Differential Refresh, what's needed?

[Wanganstyle]

So I took the input shaft bolt off my bad diff today, just to get familiar, before buying parts for my good diff. So the bolt came off waaaay too easily, I put the impact gun on there and with a super short burst, like one second maybe, the big bolt was completely loose, and I took it off the rest of the way with my fingers.

So I got the seal out w/ a screwdriver (not that hard), I could see the bearing. However, all attempts to take the bearing out failed, short of destroying the bearing. does this come out through the back after removing the LSD unit?

Thanks

top pinion bearings comes out under seal after you remove the pinon gear, the pinion gear must be pressed out with proper press and set to avoid damage to threads. inner pinon bearing must be pressed off the pinon gear

LSD carrier bearings are press fit also, you will want a dial indicator and a Drag tool; part numbers for BMW factory tools are listed in the above TIS link :)

[blefevre]

is NOT torqued to crazy high value.

here is the FACTORY BMW procedure :)

http://tis.spaghetticoder.org/s/view.pl?1/00/50/34

Bentley says the input bolt is ~230 ft/lb min?

[Wanganstyle]

Bentley says the input bolt is ~230 ft/lb min?

perhaps inch pounds or incorrect?

BMW TIS uses a Drag indicator to set this, NOT torque.

if you torque your pinion 30mm nut to 230lb-ft.........you will have a dead diff after you drive it for a while!!!

from the factory TIS; when swapping the imput seal-


************
If the friction torque determined prior to assembly, plus 20 Ncm for the new shaft seal has not yet been reached, continue tightening down the nut until this level of friction torque is reached.

Example:

Friction torque prior to disassembly 160 Ncm
New shaft seal + 20 Ncm
Adjust friction torque to 180 Ncm


************

No where have I ever seen Torque when looking at diff setting; its always by DRAG :)

[blefevre]

Well yes, that is friction torque. The bentley stated the bolt will be at ~230ft/lb minimum and you continue until you have the correct friction torque. I will check it again when I get home.

The service manual you linked doesn't list the torque spec, it says to reference a table, then continue torquing until the correct friction torque is reached.

[Wanganstyle]

Well yes, that is friction torque. The bentley stated the bolt will be at ~230ft/lb minimum and you continue until you have the correct friction torque. I will check it again when I get home.

The service manual you linked doesn't list the torque spec, it says to reference a table, then continue torquing until the correct friction torque is reached.

There is no reason to believe the bently, or even reference it when the BMW TIS is avail fopr $0 - straight from the factory.


Bently may be great for explaining all sorts of beginner stuff, but when it comes to serious serious work - only trust the TIS
Nobody @ a proper BMW factory or BMW dealership trained to work on your car will be referencing a bently or similar
.



I have come across issues in aftermarket service manuals for many different cars; just learned eventually to only use factory manual as its what the dealership references when they work on your vehicle.


There is no set Torque spec!!!! that's why it is not listed. I could be totally wrong, but I have not seen one listed in any TIS yet- there is just a chart of how to set the clamping bush- no "number" - its not a easy set kind of operation here......

the more you tighten the 30mm bolt, the more the center spacer is compressed- you can go as much torque as you want to add, and it will just keep going untill its so tight that the pinion bearings will bind.

if pinon was torqued to 230 lb-ft it would NOT MOVE. You can try this to a bad diff if you like to test...

Its set from the factory nowhere near 230lb-ft...

I have torn down more factory diffs than you want to know........and I can just undo the nut with hand tools if its fixed, If I hit it with my impact to loosen it comes right off- and my impact is not very powerful (electric consumer quality 18v).......


No where in BMW manuals has a torque spec- Subaru has one on their diff, jeep may also, but the style of compression on the BMW pinion is just different-


I have seen and examined with my own hands many BMW differentials RUINED by over tighten of the pinon; the bearings go, the gear mesh up changes............ all bad.

Too tight and the teeth of ring and pinon chew each other up. too loose and you can shatter the ring/pinon on shock loading.

here's the factory procedure for input seal only;

http://tis.spaghetticoder.org/s/view.pl?1/00/13/07

As stated in TIS, bolt should be marked so that the clamping bush cannot be compressed more past its current setting on re-assembly, and friction torque before and after need to be noted to add additional drag for new seal break in. using a pre-set torque value may not always meet this specification- That is why its set to drag.

And yes, rear diff is really black magic on setting - you can build a engine with all exact torque specs including torque to yield, but diffs are still fuzzy logic on drag, Bearing load, teeth mate up - there is NO 100% bianary explanation for these things.

[blefevre]

Nah man, it's cool. Just trying to see if there is another error in the Bentley. I will update tonight.

[Wanganstyle]

Nah man, it's cool. Just trying to see if there is another error in the Bentley. I will update tonight.

awesome thanks! would be good to give people a heads up so no diffs are destroyed during seal change.

We must protect the lifespan of the E30!!!!

[iamsam]

whoa man info overload!!!

This is all awesome stuff, I am super excited to see the factory BMW procedures, I will make sure to follow them!!!!

Thanks Brad and Wangan!!

[blefevre]

Do you have a link to this "technical data 33 12 2AZ"? Here is what was confusing me.

"Brace input flange with special tool 23 0 020 and tighten down nut to tightening torque,
refer to Technical Data 33 12 2AZ "

"Measure friction torque.
If the friction torque determined prior to assembly, plus 20 Ncm for the new shaft seal has not yet been reached, continue tightening down the nut until this level of friction torque is reached."

[blefevre]

Here is E30 specific. This is one detailed site!

http://tis.spaghetticoder.org/s/view.pl?2/08/62

It just says tighten, then check friction torque, tighten more, check, etc.

[Wanganstyle]

Here is E30 specific. This is one detailed site!

http://tis.spaghetticoder.org/s/view.pl?2/08/62

It just says tighten, then check friction torque, tighten more, check, etc.

b wewy kareful, we r hunnting wabbits!!!!!