e30 M3 minor rust repair.

[xworks]

And then measuring the stuff thats sliding on here.
First of which is a syncro hub. Theres 3 of these in total in the box
and while the other 2 are identical to each other, the one that fits here
has 2 small important differences. The centre's of both the other
syncro hubs are smooth on both sides, like the bit marked red below.....



The one that fits here however has a small step in it on one side,
arrowed below.....



The second difference from the other two hubs is this little groove on
one side of the outside ring, which doesn't concern us right now....



right, back to what we need to measure, one of the little needle roller
bearing collars that fits inside each gear is held up against the smooth
side of the syncro hub like so.....



and using a micrometer we're measuring to the inside ledge of
the step on this side of the syncro hub, like so......



which when measured came to 53.3mm ("B"). So the height of the
stuff we're fitting to the shaft is 53.3mm and the length of shaft we
need to fill is 53.5mm to bring them flush with the end of the splines.
So taking "B" from "A" (53.5mm - 53.3mm) gives us the gap we need
to fill with a shim = 0.2mm. That shim ain't been fitted yet though, we
have a bit of assembly to do first.

The input/output shafts and the layshaft are placed together like so.....



the middle casing is popped up into the vise and the metal around the
centre holes where the bearings fit into are heated up with the heat gun
to expand them.....



and then while it's nice and hot the shafts are offered up and
slid through like so.....





and now that the shafts are fitted to the casing we can pop on that
little 0.2mm shim we measured....



followed by the bearing collar (which was heated cause it's a tight fit
on the shaft).....



and then the bearing.....



and then 1st gear is slid on meshing with 1st gear on the layshaft
beside it.....



next up was that shiny new syncro ring.....



and finally that odd ball syncro hub, making sure that the recess cut
out of the outer ring is facing in towards the casing....



the only snag is, when fitting this last syncro hub you've got to fit it's
shift fork and rod at the same time.....



like so......



because if you don't, you'll never get the fork on afterwards, and even
if you did manage it, theres no access to knock in the roll pin that
secures the fork to the rod......




There's two other things thats probably worth noting at this stage.
The first is, theres a few little notches machined out of the end of the
shift fork rod, circled below.....



theres two ways you can roll pin that shift fork onto the rod,
1) like above with the notches facing downward which is correct, or,
2) the rod rotated 180degrees from above pic,which leaves the notches
facing upwards, which you only find out much later is the wrong way around
and means dissembling the lot to switch it around again.
(the urge to take out a hammer and chisel and beat some new notches
into it out of frustration will take a lot of effort to subdue at this point).

The other point worth noting is although the 3 shift forks will only go
together in the box the right way (they won't physically fit any other
way) it still helps a lot, if upon disassembly, you scribe onto the side
of each fork, an arrow showing which way it faces (towards front of box)
and which syncro hub it came off (ie. 5th/4th, 3rd/2nd or 1st/rev).
It just saves a lot of head scratching while you try to figure it out
upon reassembly. Which when all assembled ends up looking like
this.....





once happy that all notches and forks look like they are where they
should be, then it's time to hammer in the remaining roll pins....



With all that crap done it's back to building up the end of the
output shaft again. Remember that last odd ball syncro hub that
was fitted with the little ridge in the centre?....



well now we get to see why it was important the ridge faced out
this way. These two little thrust type washers......



pop into that ridge.....



which is then followed by the last syncro ring and reverse gear.....



and the little bearing for inside the gear.....



and finally heat up the bearing cone and slip it in between the bearing
and the shaft.....





next to go on is a 0.5mm shim, no measuring or calculating for this one,
every box just gets a 0.5mm shim here.....

[xworks]

new bearing is heated up with the heat gun and popped on....



the bearing the other end is only a small bit more involved. The bearing
is behind the last gear on the shaft, so the bolt and fat washer that holds
this gear on is first removed, and then the gear is pulled off its splines
on the shaft.....



with the gear out of the way, the old bearing is pulled off and new one
heated and slid on......



and then it's time for the first bit of shimming.
When the gear is pushed back on the shaft on top of the new bearing,
its up to the fat washer and bolt to hold them all secure and tight.
If the gear was pushed back on the shaft and wasn't level
with the top of the shaft, then when the fat washer and bolt were tightened
down the gear and bearing would still be free to wobble around a
little underneath it.
So, with a depth gauge, the length of exposed shaft on top of the bearing
(marked X below) is measured....



"X" was measured at 34.8mm.
Then the length of the gear is measured (Y)....



and as you can see it was 34.7mm
So a 0.1mm shim is needed to bring the gear flush with the end of the
shaft.....



shim fitted, gear heated up and slipped on, fat washer refitted and
bolt loctited and tightened back in place. Layshaft finished.....



After that it's on to short the input shaft, replacing the front bearing
first (making sure the recess in the outer race for the circlip is facing
away from the gears as pictured).....



and then the little bearing in the end of the shaft.
(new one fitted, old on on bench).....



After that it's on to the output shaft which holds the majority of
removable pieces.There's a collar at one end of the shaft which
means the shaft is built up in two steps as arrowed....



first up the long side is built up. The shaft is placed into special tool
p/n 959axlestand to hold it secure......



first up one of those little double row needle bearings
(like the one shown below) is slid on.....



then 3rd gear and a syncro ring is slid on....



followed by a syncro hub. The syncro hub is a tight fit on the shafts
splines so it's heated with the heat gun first to expand it and allow it
to push on by hand (soon to be burnt hand).....



after that its another syncro ring (they're all identical to each other),
followed by 2nd gear....



another of those needle bearing slides inside the gear
(like the one pictured below).....



this bearing however isn't a snug fit on the shaft, instead it runs on
a removable collar like below, so the collar is slid down in between the
bearing and shaft.....





After that, next on is the centre piece of the worlds most expensive
gearbox bearing (yeah that price really got to me)....





And thats as far as can be built up this end of the shaft at the
moment, so, the shaft is rotated in the stand and we start building up
the other end.....



first on this end is another of those double row bearings....



followed by 4th gear and it's syncro ring.....



and then a syncro hub (again heated in the centre to slide on easy)....



and with the syncro hub in place, last to go on this end of the shaft is
a fat spacer and a circlip to hold everything in place. Again everything
has to be held on tightly this end of the shaft, there can be no play for the gears
to move around.
So, with that in mind, that spacer under the circlip comes in a range
of different sizes, going up in small increments. Pop the circlip on
without the washer under it, measure the gap below it and then use the
largest size spacer that will fit to keep everything packed tight
(use a new circlip going back, they only cost buttons and if the
old one fails it'll cause the box to go "boom") .....





and with that done the input and output shafts are fitted together
(one just slides in to the end of the other)....





and then the whole lot is popped back up in to the stand again
for a bit of measuring.....



The measurement we're after this time is is marked "A"
in the pic below. And it's the distance from the top of
the expensive bearing inner race up to the next "ledge"
on the shaft at the top of those splines.....



same idea again as the layshaft shimming. The stuff thats going
on the shaft here needs to be held tight by the stuff that comes
on top of it. Only problem is the stuff coming on top of it will only fit
down as far as this "ledge" in the shaft. So we've got to make
sure this stuff fits on level with the top of the ledge.
And this is done by measuring the piece of shaft with
a depth gauge ( "A" = 52.5mm)......

[xworks]

With everything cleaned, checked and replaced if worn, it was time to
try and figure out how it all went back together.
Starting with the rear casing......



and this little collection of bits whose job it is to spring load the gear
lever when your moving it from side to side in neutral....



smaller of the two springs dropped in like so.....



flat washer and circlip on top, to stop it wandering....



and then this little tube whose job it is to grab the selector rod....




as you can see the tube has a specially cut internal section which allows
the selector rod to side back and forth inside it undisturbed, but when
the selector rod is rotated left or right (when you move the gear lever
left or right) it rotates the whole tube left or right......



the selector rod is kept free during all this movement thanks to 4
little rollers stuck on the shaft (one hidden underneath)....



the tube sits into the casing like so.....



making sure the leg attached to the tube is the right side of that first
spring that was fitted.....



the second bigger spring goes on next, the legs of which sit like below......



followed by a washer and circlip.....



next up is the method of stopping the gear lever from being pushed
to far to the left or right. The little tube just fitted has an elongated
notch cut into it like so......



and when in place this notch lines up inside with this hole on the casing.....



into which is screwed this little locater bolt....



before screwing it in, its given a dab of loctite to lock it in place but
also to seal it so gearbox oil can't weep out.....



when it's in theres the head of the bolt and the casing has been drilled
for lockwire.....



so some lockwire is fitted....



when all that crap is fitted this next little selection of stuff is hammered
in, in this order....



into this hole....



this little plunger gives you that extra bit of spring force to overcome
when your pushing the gearlever all the way over for reverse. A little
bit of gasket sealer on the sides of the black plug below on fitment
helps keep it oil tight.....




After that it's onto the centre casing and the fitment of the worlds most
expensive gearbox bearing. Only fitting the outside piece of this at the
moment, the inner ring will be used later....



the aluminium casing around the bearing hole in the centre of the casing
is given a nice heating with the heat gun, to ever so slightly expand it,
which allows the colder bearing to slide easily into place. The bearing
only fits in from one side as theres a ridge to stop it sliding through....



then the two little countersunk allen key head bolts are fitted through
the casing and screwed into the 2 little retainer tabs which stops the bearing
falling out the other side. Bit of loctite on these two bolts does no harm....



After that it's on to the replacing the 2 layshaft bearings......



the front old one is pulled off....

[xworks]

and these 3 selector forks are solidly connected to 3 rods....
(only 2 forks in picture)



Theres also another rod in there too, its the "selector rod" and its
the only one thats connected to your gearlever. When you move your
gearlever right it rotates right, move your gearlever left it rotates left.....



attached to this "selector rod" (the funky green one) is a finger (also
funky green). And as mentioned when you move the gearlever left
and right when in neutral the green rod rotates left and right moving
this green finger up and down between the 3 selector fork rods
(funky purple, blue and yellow).........



move the gearlever all the way to the right, the selector rod
rotates all the way to the right and the finger moves all the way up
to engauge with a cut out in the purple rod. Now when you move
the gear lever back or forward in to 4th or 5th gear position the
green finger moves the purple rod backwards or forwards, which
in turn moves the purple fork which moves the syncro hub forward
to engage 5th gear or backwards to engauge 4th.....



Leave the gear lever in the middle position and move it backwards
or forwards between 2nd and 3rd gear position and the green finger
hooks up with the blue shaft and fork moving the 2nd/3rd syncro hub
locking in either 2nd or 3rd gear.....



and finally move the lever all the way to the left over for reverse
and first, the green finger gets rotated all the way down to hook up
with the yellow shaft and either select 1st or reverse down the back
of the box......



And thats roughly how it all works,

I think,

maybe.

The main reason for pulling the box asunder was I wanted to replace
the bearings in there. A couple of months before pulling the car off
the road a nasty clicking sound came into the front end of the gearbox,
so we pulled the box and stripped off the front casing to try and find
the culprit before the clicking progressed to a knocking and finally
the big "boom". The front input shaft bearing looked ok, a little bit gritty
when spun but not the cause of the noise....



and then we went on to the one under it, the front layshaft bearing.
We had a sneaky feeling this could have been the cause of the noise.
Call it a sixth sense if you will but there was something bugging us
about this bearing. Here's the two of them side by side, it takes a
sharp eye to spot the difference, but if you look close enough you
should be able to see the tiny defect.....



Yeah, the bearing cage had completely shit itself, allowing the balls
to move around as they pleased, which had resulted in the clicking
sound. The cage that holds the balls spaced out is made out of a hard
plastic type stuff (*might not be correct technical term). And the reason
it had broken up was the inner race of the bearing had started to pit,
and got worse over time, which meant the little balls were bouncing
over the pothole created......



Eventually it got to hard for the plastic cage to hold on to the balls
as they bounced and it broke up. Next up had the box been kept
driven would probably have been one of the balls getting jammed
or popping out of the bearing, either of which would probably have
resulted in a nice little explosion of bits inside the box. Thankfully
due to that clicking sound we got a little warning that the end was
coming. At the time we only replaced the front end bearings because
the car is my everyday car and I needed it back on the road as soon
as possible. So now it's all coming asunder and all the 5 main bearing
in the box are getting changed.....



Number 4 and 5 in the pic above are on either ends of the layshaft (bottom shaft)
and are just normal bearings available aftermarket. The front layshaft
bearing (on left in pic) 25x62x17mm was replaced with a Timken
bearing p/n 6305/C3. The rear one (on right) 72x30x19mm was
replaced with a SKF bearing p/n 6306/C3....



Number 3, the rear bearing on the output shaft is identical to
the number 5 the layshaft rear bearing, and again was replaced with
a SKF bearing p/n 6306/C3.....



So that just left us with number 1 and 2 to source. I could only get
these from the main dealer as they're a bit odd ball bearings.
The first one (number 1 bmw p/n 23121204580 ) the input shaft bearing
is special because it has a groove cut into the outside race to take a circlip
as seen below......



This must be made from rare minerals as thats the only reason I can
see why it cost 80 something euro! But if that one was made from
rare minerals then they must have to travel all the way to the moon
to get the stuff to make bearing number 2 (bmw p/n 23231205191).
This is a 2 piece needle roller bearing and it weighs in at 208 euro.
That hurt.....





With all the main bearings done it was time to move on to the smaller
ones. The red arrowed one below was changed because it has one of them
hard plastic races holding it together and these get brittle over time....



bmw p/n 23221207784.......



all the blue arrowed ones are the little double row needle roller
bearings that fit inside the gears. These were available after market
but had a 4 week order in time so I just got them from the main
dealer instead (bmw p/n 23221228279)......



Only 2 of them little needle roller bearings ride on the shaft, the rest of
them ride on their own little separate inner race's pictured below.
None of these needed replacing as there was no marks on them
and they showed no signs of wear.....



The other thing that I wanted to pay special attention to while in here
was the syncro rings. 1st gear had a habit of being awkward to select
in this box in stop go traffic, especially when warm. So all the syncro's
got checked while assunder.....



to check them the syncro ring is placed on top of it's gear, lightly pressed
down and the gap (arrowed below) measured with feeler blades.....



for a new syncro ring sitting on a gear the gap is 1.0 to 1.3mm
if the gap on the old one is below 0.8mm she kaput.
The only difference is reverse gear, 0.5-0.6 new less than 0.4mm replace.
Given I couldn't fit a fly's pubic hair bewteen my 1st gear syncro
ring and the gear I could safely say it was fu*ked...



One of the other things that got checked was the shift forks. These
sit into the groove on the syncro hubs and push them backwards and
forwards. As the syncro hubs are allways spinning and the fork are
allways held still, the side faces of the forks can tend to wear, giving
a slopply gear change (you have to move the gear lever move before
a worn fork actually starts to move the syncro hub)......



minimum fork thickness is 4.8mm, thankfully mine were all good to go.....

[xworks]

With the driveshaft out of the way, there was no avoiding it any longer,
next up was going to be the big aluminium box full of gears.
First thing to note is, the following waffle is all about the Getrag 265/5
dogleg gearbox. The bit thats worth noting about that, is, the 265/5
gearbox is the dog leg gearbox, meaning that 1st is all
the way over to the left and down (under reverse).
The Getrag 265/6 which was also fitted to M3's (mostly
American versions I think) is the non dog leg 5 speed overdrive gearbox.
It pays to make a mental note of the difference between a 265/5 and
a 265/6 cause when your looking up parts on real.oem or looking up
the manual for torques or proceedures theres a difference between
the two internally. And its frustrating ordering in parts for your
box only to find upon collection that the bits you've ordered are
for the wrong one and are non refundable. (And despite trying,
no amount of hammering will make them fit)
On to the actual disassembly of the box. This is
a very complicated proceedure, and I'm now going to attempt to
explain the highly skilled, meticulous, disassembly of my gearbox.
Measure in exactly 253 mm from the rear output flange and
up 176mm from the bottom of the casing on the left hand side and
mark this spot with a large red x.....



Then hit this spot an unmercyfull wallop with special tool part
no. 959sledgehammer.....



and ta-daaaa......



(click on this link for full size image:
http://www.xworksmotorsport.com/m3%20build%20(12)/gearbox%20panaromic.jpg)

For anyone who's not comfortable using the sledge hammer method of disassembly,

the the full strip down procedure is given here in the Bmw workshop manual....[/color]

http://www.bmwtechinfo.com/repair/main/421en/index.htm

[color=white]click the link, click on the "contents" box, click on "23 manual transmission"
and then make sure you click on the right gearbox 265/5 or 265/6.
With the gearbox assunder it can help a little to know how all this crap in
here is supposed to work. If for no other resason just so you can easily
identify what part of the rebuild has gone t*ts up.

WARNING: You will most likely know less about the workings
of a gearbox after reading my explanation than before reading it.
Inside the gearbox casing theres 3 main shafts.....



Theres one or two cogs missing from the above picture but its enough to
get the idea. Pictured are the 3 shafts, the input, output and layshaft. The first
thing thats makes fuck all sense, at first, is how is the top shaft in the picture is
in fact two shafts (input shaft & output shaft)?
The input shaft as seen below is short and only has one gear
and one bearing on it, and in the end of the input shaft is
a hole with a small roller bearing in it which allows the other
shaft, the output shaft, to sit into it and be supported......



new bearing in the hole, old one out on the bench....



The whole idea behind this setup is that the two shafts can move at
different speeds to each other. The input shaft at the front of the box
is connected through your clutch to the engine flywheel. So, with
the clutch let out this shaft is always spinning at engine speed. The whole aim
of the game is to pass this drive through a series of gears to reduce the revs
coming out the back of the box. 1st gear reducing it the most, working
right up to 5th gear which in this box is 1:1 ie one turn in = one turn out.
And heres the selection of gears it uses to do this......
(1st and reverse are missing from right of pic)



With the input shaft spinning the one gear thats solidly connected
to this (5th gear) is also spinning....



and because 5th gear on the input shaft is also connected to
5th gear on the layshaft (underneath it) then the whole layshaft
is also spinning too. And because basically the layshaft is one
big solid lump of metal, then all the other gears it's in contact with
are spinning too.
So, gearbox in neutral, engine turning over, all thats marked
red is spinning at engine speed....



So how the fu*k is the output shaft coming out the back of the box
not spinning if all the gears on it are spinning?......



The answer is all the gears on the output shaft (top shaft), while sitting on it, are
not actually connected to it. Between the centre of the gears and
and the shaft are little roller bearings, so no matter how fast you
turn the gears you wont turn the shaft.....



So to get the output shaft to turn you have to "lock" one of these
gears to the shaft and to do this you use the syncro hubs.....



The syncro hubs sit in between the gears and have two main pieces.
The centre of the syncro hub is connected solidly to the output
shaft by splines (red bit in pic below) and the outside part (blue bit)
is also splined onto the red bit, the only difference being the
blue piece can slide over and back on the red piece.....



The reason it can slide over and back is so it can lock on to these little
teeth on the side's of the main gears (red piece below) while also staying
connected to the centre of the syncro hub.........



So when the blue piece of the syncro hub slides over to grab these
red teeth in the pic below it's also still connected to the centre piece
of the syncro hub, and bingo, you've just locked one of the gears
to the output shaft. Now the output shaft is being driven......



In the pic below the red syncro hub is slid to the
left and the gear to the left of it (3rd gear) is "engaged" and locked to the
output shaft, hence the output shaft (To Differential) is now
been driven by the engine.....



The other bit in here thats important is the syncro ring.....



It sits in between the gear and the syncrohub and it has the shittiest job
of the lot. When the syncro hub moves over to grab them little teeth
on the side of the gear and lock it on to the shaft it runs into a little
problem. The hub and the gear are rotating at different speeds. So
if one tries to mesh with the other like this then theres going to be
a horrible sound in the gearbox and a whole lot of new little bits
stuck to that drain bung magnet. What needs to happen is the two
need to be rotating at the same speed so they can lock together.
This is where the syncro ring comes in. The inside of the syncro ring
is cone shaped.....



and the bit of the gear it slides on to is also cone shaped.....





so as the syncro hub sleeve moves across it grabs the brass syncro
ring first and then squeezes this up against the gear to get it rotating at
the same speed and then as they synchronize it can then slide fully across
and lock onto the gear......



And then at last, the final bit, for anyone left that hasn't got bored and
logged out to go look for porn sites. How does moving one simple
gear lever from up in the drivers seat move all these syncro hubs
down in the gearbox?
The box has 6 gears, 1st 2nd 3rd 4th 5th and reverse that can be selected.
Each syncro hub can slide forward or back to select the gear in front
of it or behind it, so thats 3 syncro hubs that need to moved.
A brass "selector fork" sits on to each one of these syncro hubs....

[xworks]

Evenin all,
Bit of a gap since the last update, was so busy working on the car
I couldn't get time to write up all the work. Managed to get a lot
done since the last update.

And when you run that through the "Babelfish Bullsh*t Translator" it comes out
as:
Ages since the last update cause the shed feels like the inside of a freezer
at this time of year and everything you pick up brings frostbite a step closer.
The heater heats itself and nothing else and the camera took on a life of its own
and decided to mix up all the photos for the crack.

So heres what actually got done.
The driveshaft....




despite looking their age both joints on the shaft still rotate in all directions
without any sticking or tightness, so a clean up and they're good to go.....




what is getting changed is the centre bearing. Before splitting the shaft
a quick check for the original marks to help align it correctly when going
back together. If they're gone, two small dabs of tipex will do.....




collar screwed back off the shaft and splines slid apart.....



a slice around the rubber allows the outer piece of carrier bearing
to be cut away (along with tops of fingers).....



pop the circlip and the large washer behind it off....



and then simply pull the bearing off the shaft with the pullers....



which is how it goes in the fantasy world of "workshop manual land".
However in the real world no amount of pulling, beating or swearing
would remove the bearing. So the special bearing removing tool had
to be used, also known as an angle grinder.....





shaft gets a quick lick of sandpaper to clean up where the new
bearing is going to sit....



the new carrier bearing has the bearing recessed on one side like so......



and flush on the other side like so.....



the bearing in the centre is heated up using the heat gun....



which allows it to slide up on to the shaft easily, with the recessed
side facing in and the flush side facing out like so.....



then the washer and circlip go back on and if you've fitted the
bearing the wrong way around you now realise the cirlip won't
reach in to fit in it's groove anymore, which will mean the whole thing has
to come off again to be flipped around, which is nice......





then the threaded cup is slid back up on to the splines, some copper
grease on the splines and then the other half of the shaft is slid back
on with the white marks aligned....



The threaded cup isn't tightened up to lock the shaft length till it's
all refitted back on the car and extended to the correct length....



The last thing to do then was rebolt the rubber "guibo"
or donut onto the gearbox end of the shaft. Mine was in
good nick as i'd only replaced it a while back. Unfortunately
shortly after replacing it I read about the E34 M5 one
(p/n 26 11 2 226 527) being a straight forward replacement,
only its alot thicker and as such most probably longer lasting,
(f*ck it anyway)......

[CorvallisBMW]

Wow. I was getting ready to rebuild my diff this winter, but after seeing all this and the amount of work it takes I may just send it to a shop. that PDF you linked takes like 50 pages to explain it and uses dozens of special tools. Not to mention I'm rebuilding my limited slip unit at the same time since mine seems to no longer be working.

[xworks]

Damn good blow-by-blow writeup there.

By the way, that diff bushing looks like the reinforced M version. Do you have the part# or which model/year it came from?

Sorry for the delay replying I bought the bush here.....

http://www.c3bmw.co.uk/StockItem.asp?categoryID=73&subcategoryID=0&productID=1249&oRef=-1&section=2&Item=unassign

[evilnickwong]

Damn good blow-by-blow writeup there.

By the way, that diff bushing looks like the reinforced M version. Do you have the part# or which model/year it came from?

[funcrew]

Wow thanks for posting step by step pics. This thread deserves its on subforum.

You said it. Totally over the top workmanship and photo-documentation. Makes me embarrassed about how I take care of my E30. Also a classic thread title, "minor rust repair."

[///M42 sport]

Wow thanks for posting step by step pics. This thread deserves its on subforum.

[xworks]

(continued from previous page)
With all that done, we pop the crownwheel and cups back off again,
and start fitting up the pinion. First up drop in the outer pinion
bearing.....



followed by the seal.....



and then the inner pinion bearing is pressed on to the pinion shaft
and then the colapsable spacer(arrowed) is dropped on as well.....



this lot is then pressed into the casing and up through the outer
bearing. The pinion flange is popped back on and special tool
reattached.....



and the pinion nut is retightened.....



Theres no torque for this nut as again your using it to "preload" or
squeeze the two bearings below it just the right amount.
When retightening it you can feel the nut first tighten a little bit as
the outer bearing gets squashed up against the collapseable spacer,
but the pinion still is able to slap up and down in the direction below....



What has happened here is the both bearings have not been squeezed
close enough together yet and they can lift up and down off their races
because that collapsible spacer is keeping them apart.
So, the nut is tightened down more, slowley, crushing the collapsible
spacer till theres no up and down play and the bearings are sitting snugly
in their seats and then ever so slightly tightened again in little steps till the
right preload is got on the bearings. This extra bit of squash (preload)
on the bearings is done because when you nail the accelerator pedal
if the bearings were just fitted loosely they'd start to lift out of their
races and the pinion would start it's break for glory out through the
diff casing. Instead of leaving two nice big black tyre marks you end
up leaving one nice big trail of diff oil and gears.
Again there is a special tool for measuring the correct preload and
the figures for it are in the manual.

With everything tightened up correctly and a quick splash of holy water,
the lock washer is bent in to place....



casing is flipped over and crownwheel unit and cups refitted....



and halfshaft flanges refitted....



And then finally on to the most important check of the lot,
tooth contact. Some engineers blue....



spread evenly on 3 crownwheel teeth.....



and then rotate the diff gears by turning the front pinion flange while
putting a bit of loading on it by holding one of the output flanges loosely....



and what your left with should be a marking on the crownwheel teeth
of where the pinion teeth are contacting it. What your looking for is a
nice fat contact patch in the middle of the tooth, something like below....



If the contact patch is too high up towards the tip off the tooth you'll need
to move the pinion gear closer to the crownwheel by putting a fatter
shim under the inner pinion bearing.
And if it's too low to the base of the tooth you'll need to fit a thinner shim
to move the pinion gear back away from the crownwheel.
If the contact patch is too far towards the inside of the crownwheel tooth
then you've got to change the crownwheel bearing cup shims to move
the crownwheel away from the pinion gear.
And likewise if the contact patch is towards the outside of the tooth
change the cup shims to move the crownwheel towards the pinion
gear.
Again if none of the main components have changed during the overhaul
then the contact patch should be pretty close to right, but you still
gotta check. If you get the tooth contact patch badly wrong, then don't
worry to much about it, you'll be getting a chance to rebuild it all again
after a few miles, when it sh*ts itself.

After all that mind numbing crap is done, a bit of gasket sealer....



under the gasket and a little smear above....



bolt the rear cover back on....



pop the speedo sender back in with a fresh o ring....



bungs back in and fill with oil and thats it....





and all that waffle was for a case with 2 gears and 4 bearings,
I'm buying a new keyboard for whats coming next.....



till next time....

[xworks]

With that done it's on to setting up a clean area to place the parts
on once their washed.....



Below is a picture of everything and a list of what we've chosen to replace.....



(blue font is the changed parts)
1. Pinion flange
2. Pinion
3.Pinion nut lock ring (oe) 23 21 1 490 120
4. Pinion nut
5. Collapsible pinion spacer (oe) 33 12 1 744 368
6. Pinion seal (oe) 33 10 1 214 099
7. Pinion shim
8. Pinion inner bearing (aftermarket)
outer race- SKF fk-hm 89410-2-cl7a
bearing- SKF ak-hm 89449-2-cl7a
9. Pinion outer bearing outer race (aftermarket)
SKF fk-h 88510-2-cl7a
10. Pinion outer bearing (aftermarket)
SKF ck-hm 88542-2-cl7a
11. Crownwheel bearing cup shim
12. Crownwheel bearing cup O ring (x2) (oe) 33 11 1 214 144
13. Halfshaft flange
14 Crownwheel bearing cup
15. Crownwheel bearings (x2) (aftermarket)
outer race- SKF fk-lm 503310
bearing- SKF k-lm 503349-cl7a
16. Halfshaft flange seals (x2) (oe) 33 10 7 505 602
(comes with part 17's included)
17. Halfshaft lock rings (x2) (oe) (comes with above)
18. Limited slip differential and crownwheel
19. Casing
19. Casing gasket (oe) 33 11 1 210 405
20. Speedo sender locking plate
21. Speedo sendo and O ring
22. Z3 rear cover

In the list above the renewed parts listed in blue are marked
(oe) for bought off BMW, and (aftermarket) were sourced
at a local bearing supplier. The bearings sourced "aftermarket"
are either SKF or KLM bearings which is exactly what you'll
get from Bmw, only they won't come in a nice little Bmw jiffey
bag, but they will cost less than half the main dealer price.

With everything together it was time for reassembly. I've taken
the decission not to open up the limited slip diff unit as before
the car came off the road it was working perfect, and I know
if I open it I'll start replacing things, and, well, that money can
be better spent elsewhere.
Beer.

First up on the list of reassembly is to press on the crownwheel
bearings.....






then fit the races for these bearing into the crownwheel cups....



flip the cup over and pop in the halfshaft seals. The seal goes in till
it butt's up against the back of the bearing race(arrowed)....



One thing to be careful of is when driving in the seal up
against the back of the bearing race, is, if you go a little to
far you can possibly knock the bearing race back out a bit.
So, when done the cup is flipped over again and the race is
tapped back in again to make sure it's home.



Then on to the pinion bearing races. First up the inner bearing race.
This was the one that had the shim under it, so, shim dropped in
first and then bearing race popped in on top of it....





then flipped over and the outer race fitted....



With all the races refitted the next thing to be done is pop back in
the diff unit and refit the cups and shims(arrowed) remembering
to keep them to the sides they originally came out of....



with the cups bolted back in tight both sides it's time for the first
setup check. The cups should now be holding the diff unit tightly,
it should be able to rotate but have no noticeable play in the direction
of the arrows below....



and aswell as having no play the cups should also be slightly squeezing
the diff bearings which is known as preload. This preload is measured
by a special tool which basically bolts on to the halfshaft flange and
measures how much effort it takes to rotate the crownwheel. To little
force, remove some shims which tightens up the preload on the bearings
when the cups are refitted. To much force required to turn it and
you pop in the next size up shim to ease off the preload.
There is figures given for it in the workshop manual.
If all you've changed in the overhaul is bearings and everything else is
original to that casing going back together then odds are the shims
that were there already will be fairly spot on.
If you've built a lot of diff's there's another special tool you can use to
measure the preload....

[xworks]

Evenin all,
Thanks again for the kind words, much appreciated.
As mentioned in the last post we're taking a break from the shell
for a while and moving on to the drive train overhaul, and, starting at
the back and moving forward, first up we have the differential. That
magical lump of metal that sits in the back axle and lets you move
in a sideways fashion when the opportunity arises.
First and foremost, as usual, we'll just take a second to say the
obvious, this isn't a guide on how to build a diff, for that, go here
http://bmw.ctcms.net/BMW/Software/E3...0Bmw%20e30.rar
(password to unzip the files is bmwfaq )
download the full workshop manual and follow the smart people
at Bmw's guide, The section on the diff starts at 33-101.
Unfortunately they don't use a large selection of hammers to do
their overhaul, so I have trouble relating to it.
Anywho, back to my diff. This is a medium case diff as identified
by the 8 bolts that hold on the back cover, the small case diff
has 6 bolts holding on the rear cover and the large case diff is
easily identified by snapping your spine while trying to lift it as
it weighs 14 ton.
First up pop the 8 bolts off the rear cover and remove, spilling the
remaining horrible smelling diff oil over your clean bench.....



then using special tool no. 959bigbar, we popped out the halfshaft
flanges....



in the middle of the diff that big gear you can see is the crownwheel
and to the right of it is the limited slip differential.......



and next up was the crownwheel bearing cups. One on each side of
the diff and these house the crownwheel bearing outer races which
hold the diff unit in place. Theres a ring of six bolts that hold each
one in place, and before you undo them it pays to take a second to
notice that each cup has a square notch on top of them (as arrowed)
which alligns with a corresponding notch on the diff casing (as arrowed)....



When you undo the ring of bolts and pull out the cups the diff unit
will drop inside, so you can either let it drop and damage it or put
your hand under it and damage it instead. If your lucky enough to
have an assistant helping you then you'll not need me to tell you who's
hand to use. When you pull the cups you'll notice a shim (arrowed),
this will either be still stuck to the casing or the cup. Keep these shims
matched with the cup they were fitted with and mark which side they
came off, they'll need to go back on the same side or things will start
to get funky. When the cup's off you can see why it has a notch to
show you why it needs to be fitted this way up. In the pic bellow
you can see the cup has an oil drilling (arrowed) which lets oil splash
in the top of the cup and drip down on to the crownwheel bearings, and
obviously if you fit the cup any other way the oil aint going to drip
anywhere....



With the crownwheel/diff unit carefully lifted out all thats left in the
casing is the pinion......



to remove this you gotta take the pinion flange off the front of the
pinion....



first up bend back in the little piece of the locking washer from the
recess to let the nut loosen.....



and then use special tool part no.959rustypieceofbar....



which is basically a piece of bar with holes drilled into it to allow
2 M8 bolts to fit through it and bolt up to the pinion flange and hold
it from turning while loosening the nut....



once the nut's off, the flange should lift off, if it doesn't smack it repeatedly
with a large hammer while searing at it loudly.....



pop the nut back on to protect the threads from stray hammer blows,
it turns out fine threads and large hammers do not mix,
I know, it suprised me too....



pry out the pinion seal.....



and then strap on a pullers and push out the pinion.....



(I know the pullers is crooked, if it really bothers you, tilt your head
to the side)
and bingo, one pinion and a front and rear pinion bearing and
although its hard to make out in this pic, also a collapsible spacer ....



If your diff has started to whine, rumble or make strange noises then
usually it's these bearings that have started to sh*t themselves. Everytime
you drop the hammer in your car and unleash all that horsepower it's this
pinion gear that try's to burst it's way out of the differential casing and these
two bearings that have to persuade it to stay.

next up is to strip out the bearing outer races starting with the pinion pair
in the diff casing. The inner pinion bearing race drives out down into
the casing and flip it over and the outer race drives out through the top...



the two races out and the next thing to make a mental note of, is the
inside race has a shim between it and it's seat in the casing(arrowed).
This has to go back in to the same spot upon reassembly or again
things will get funky....



next up the crownwheel cups, drive the oil seals outwards.....



and flip it over and drive the bearing races out....



With everything stripped down it's time for clean up. As you
can see below the casing was covered in a fine blend of crap
and rust.....



So we break out the "de-scaler", as usual I've no idea what the rest of
the world calls this tool. It's air operated and when you pull the trigger
all them little needles plunge up and down pounding the crap out of
whatever you happen to be holding it against.
It does a fine job of removing all the loose crap and rust from the
casing and then proceeds to evenly spread it around the rest of the
garage while deafening you in the process.....







casing cleaned, it gets a coating of red oxide, before a final coating
of satin black....



the rear cover (which I think is a Z3 item with the extra cooling fins)
gets a steam clean. One bit that gets a little special attention is the
little breather hole. Gotta make sure this ain't clogged up, as if it is,
when inside the diff gets hot theres no where for the expanding warm
air to get out and it ends up pushing oil out past your lovely new
seals...



after that it's on to pulling off the crownwheel bearings, these little
fu*kers were tight and needed the use of the bigger pullers....



the other little thing to be careful of is the thin trigger wheel
shown below pressed on to the diff unit. Its the trigger wheel
that the speedo sender reads to tell the speedo gauge up
on the dash how far over the speed limit your going. As it's
thin, it'll bend easily and if your unlucky you'll reassemble everything
only to find out your speedo no longer works, which will mean stripping
everything back down again and repairing or replacing it, which is nice.....



after that, it was on to pulling the pinion inner bearing. To say this was
tight really doesn't convey it accurately, b*stard tight would be
a better discription. One of those one's where you strap the pullers
on and start winding, and winding, and winding, and then stop, and
rap rags around the bearing in the misguided thought that if the bearing
explodes they'll save you from harm, while the truth being that if it does
go you'll now have bits of dirty rag stuck in you along with bits of bearing....



and eventually theres a large crack and after you check for
shrapnel wounds you realise the bearing has started to come.
(mental note, must look into health insurance.)

Then with everything stripped down it's on to the "decontamination unit"....



Two basins of paraffin, one to wash the heavy crap off and the second
to rinse the smaller stuff off and then finally aerosol cans of parts cleaner
to give them the final rinse.

[funcrew]

Mind boggling. If this were being farmed out to a shop at $90/hr for labor, it would end up costing more than a new Veyron.

And holding down the opposite end of the bell curve, I will be roller-painting my POS sedan with Interlux Brightside marine polyurethane, with a roughly $100 total all-in budget. Will refer back to this thread when I start thinking that it's too much work.