M3 differential? What?

[gusT_EthirT]

Please help an idiot out.
I don't know what I'm talking about, so please help me.

First of all, what is a differential anyway?
What role does it play in moving the car from point A to point B?
Is it easy to come by a M3 differential for sale?
What would one of these fetch $-wise?
Is it mad to even think about swapping an M3 differential into a 325i/S?
What would this do?
What about swapping this into a 318i/S?
What differance would this make?
Is there another less expensive differential out there that would enhance the performance of an e30? ...say putting a 318i/S differential into a 325i/S?
Is this swap even worth the trouble?
What burdens to the car would this do?
Could anyone explain to me...whatever you have time for?
Thanks so much. I worship you. :bow:
Sincerely,

Gus

[randomtask37]

i c u have much to learn, as we all did at one point. so here we go.

1. a differential is part of the drivline that connects the driveshaft to the halfshafts. and if u dont know what all that is; the driveshaft comes from the transmission and travels to the rear of the car, into the diff, to turn the rear wheels. the diff (from the driveshaft) connects to the halfshafts, which are commonly and mistakenly called axels. the halfshafts connect to the wheels.
2. ^^^
3. finding one for sale isnt TOO hard if u keep your eyes open
4. anywhere between 300-500
5. absolutly not, i have one in my 87 325is
6. swapping an m3 diff into my car changed my final drive ratio from 3.73 to 4.10 which in-turn lowered my gear ratios.
7. u dont wana swap one into a 318 becuase they had small case diffs. the stronger motor cars had large case diffs to handle the extra power.
8. see #6.
9. there are many different diff swaps u can do in e30's. it just depends on what model u have and what gear ratios are necisary for the power or use of the car.
10. i think the swap was worth the trouble. i havnt regret the swap.
11. burdens, again, depend on the orignal model of the car and what u swap. say you have a 3.73 stock diff. and u swap a 4.10, that would give u shorter ratios for quicker accelration but lower top speed and higher rpms at highway speeds. but say u swap a 2.93 for the 3.73. that would give u an outragious top speed (if u could get there) and would generally be the opposite of swapping the 4.10.

a few other pointers are:
the higher the final drive, the lower your gear ratios are going to be.
the tranny and diff work together to produce your gear ratios.
318's have small case diffs whereas m3's and 325's have large case.
LSD = limited slip differential.
lsd diffs have a "clutch" like thing in them that transfer power from wheel to wheel depending on if one is slipping or not.
there were many many different diffs placed into e30's and generally u "get lucky" to find that yours has one.

well then, that being said i may have forgot a few things so hopefully others will chime in.

[OreoGaborio]

Re: M3 differential? What?

Well... let's see if i can tackle these one-by-one... and these probably aren't the best answers, but they'll give you an idea 8)

and i'm sure by the time i'm done typing this all out, someone will have beaten me to the punch ;)

"First of all, what is a differential anyway?"
A- it's what connects the rear 1/2 shafts to the drive-shaft. they have a number associated w/ them and that number is the ratio of turns the drive shaft makes vs the number of turns that the rear 1/2 shafts make... for instance a 3.73 rear end means the driveshaft makes 3.73 revolutions to the 1/2 shafts' 1

"What role does it play in moving the car from point A to point B?"
A- turns the wheels that move the car ;)

"Is it easy to come by a M3 differential for sale?"
A- eh... not especially... but they're out there

"What would one of these fetch $-wise?"
A- depends on condition... usually an e30 M3 differential (a 4.10 Limited Slip) go for around 500 in decent shape... but that's a total shot in the dark

"Is it mad to even think about swapping an M3 differential into a 325i/S?"
A- nope, not at all...

"What would this do?"
A- the M3's 4.10 will give you a little more pep than a 3.73, because it basically shortens the gears a little bit... think about it in terms of a bicycle... shifting down one gear can somtimes help your acceleration

"What about swapping this into a 318i/S?"
A- i believe the 318's already came w/ a 4.10, but not all were limited slips... which means they're what they call an Open Differental. however some could be limited slip... you DON"T however wanna take a diff from a 318 & pop it into a 325 for reasons seen below

"What difference would this make?"
A- Limited Slip Differential quite literally does what it says.... it limits the amount of slip that occurs before both rear tires start pushing the car... w/ an open differential it's tough to do donuts & the like because once one tire starts slipping, the other tire doesn't push the car... basically the power of the engine follows what they call "the path of least resistance"... so if one tire starts spinning it's just gonna burn up... with a limited slip differential a mini-clutch (or whatever the manufacturer uses in their design) says "ok, this tire is spinning alot faster than the other one... lets give that one some power too & see what happens"... well, sorta ;) ... basically it'll give you a little added traction when you're accelerating out of a corner

"Is there another less expensive differential out there that would enhance the performance of an e30? ...say putting a 318i/S differential into a 325i/S?"
A- you wouldn't wanna put a 318 diff into a 325 because BMW made two different Diffs for e30's... a large case diff (physically larger & more robust) for the 6-bangers (325's & such), and a small case diff (smaller & a little less robust) for the 4-bangers (318i & 318iS)

"Is this swap even worth the trouble?"
A- sure, if you're into auto crossing or want a little more added performance... why not?

"What burdens to the car would this do?"
A- do what? wear it out?... just driving (hard) wears the clutch slowly but surely

"Could anyone explain to me...whatever you have time for?
Thanks so much. I worship you. :bow: "
A- daaaamn right you do :pimp:


EDIT: yup... bastard beat me ;)

[randomtask37]

he just got a shitload of info.

high five!

*slaps oreo five*

[OreoGaborio]

WHAT DID THA FAHVE FINGAS SAY TO THE FACE? 8)

i love it when newbies ask specific & intelligent questions using proper grammar & spelling :up:

EDIT:... um.. .that isn't the answer to my question ;)

oh BTW Drew... you got it backwards... you CAN toss a LG case diff into a 318, just don't replace a large case with a small

[randomtask37]

oh BTW Drew... you got it backwards... you CAN toss a LG case diff into a 318, just don't replace a large case with a small

doh! well waht i ment to say was that u can put a large in for a small. but, its kinda overkill. but dont swap a small for a large as u will rip it to shreds.

p.s. IM rick james bitch!

*slaps pete in the fez*

[gusT_EthirT]

Thanks so much for the help.
Glad you could spare the time...
Sorry for being the slightest bit concerned with grammar.
haha... now i'm just playin with the whole following the grammar thing...
Piece out
Gus

[AdamF 88iS]

It is true that 318s have 'small case' differentials, you can still put the big case from a 325 or M3 into a 318, this is an upgrade to consider if your driving style/car setup would cause extra strain on the small diff.

[bimmerphile]

i love it when newbies ask specific & intelligent questions using proper grammar & spelling :up:

I like this guy already. none of this "tell me EV3RYTH1NG EVAR about a differenshul!!!!111one"

[iXer]

Something that few mention that I wan't to add :
The final drive ratio of the differential tells you how many turns the driveshaft must turn before the half shafts (the wheels) have turned over once.

[KenC]

"tell me EV3RYTH1NG EVAR about a differenshul!!!!111one"

That's funny because I just read that same exact quote on DTM earlier today :nice:

[bimmerphile]

"tell me EV3RYTH1NG EVAR about a differenshul!!!!111one"

That's funny because I just read that same exact quote on DTM earlier today :nice:

:rofl:


SNAP

[OreoGaborio]

Re: M3 differential? What?

Something that few mention that I wan't to add :
The final drive ratio of the differential tells you how many turns the driveshaft must turn before the half shafts (the wheels) have turned over once.

"First of all, what is a differential anyway?"
A- it's what connects the rear 1/2 shafts to the drive-shaft. they have a number associated w/ them and that number is the ratio of turns the drive shaft makes vs the number of turns that the rear 1/2 shafts make... for instance a 3.73 rear end means the driveshaft makes 3.73 revolutions to the 1/2 shafts' 1

8)

[iXer]

OreoGaborio: He gave the poor guy too much info, didn't see that one :oops:

[EVOIIIM3]

I have one for sale $400
Stock M3 4.10 LSD, in great shape.

You can see how clean inside it is.....