My LSD just blew up, now I have some questions..

[strictlyJDM]

Went to move my car, right when I pulled off, I heard a loud clunk from the rear end and now im getting extreme clutch chatter even when going straight..cant even go over 5 MPH cause its that bad.

Its a 3.15 LSD

now my questions,

I want to replace it with another 3.15 but since I have a 540i/6, I can only source diffs from another 540i or 750i's right? There are medium case and large case diffs ?

I also read that 3.15 LSDs off the 7 series, I would need to swap the input flange going from driveshaft to LSD?

Share some insight on LSD compatibility please!

[me78569]

3.15s came in the 750 sport models. The stock diff from a 540 was with a 2.81 or a 2.93 (both open diffs). The large case diff is what you need. You can't pull a diff from a 530 or 525 or 535 as a direct bolt on. You are limited to either 7 series diff, stock 540 or m5 diff and 8 series diffs as far as factory replacements.

[PorscheH6]

You can only find them on '88-90 750iL. 91+ came with ASC and phased out the LSD.

I have a large case 3.91 LSD from an E34 that wold be a direct fit for your car, if you are interested.

[me78569]

3.91 lsd would be crazy in a 540/6 haha I say do it....

[strictlyJDM]

3.15s came in the 750 sport models. The stock diff from a 540 was with a 2.81 or a 2.93 (both open diffs). The large case diff is what you need. You can't pull a diff from a 530 or 525 or 535 as a direct bolt on. You are limited to either 7 series diff, stock 540 or m5 diff and 8 series diffs as far as factory replacements.

Thanks for the info...what will be needed to fit medium case diffs? too much work im assuming...axle/driveshaft swaps probably...or output shafts on the diff

also, is the 3.15LSD only out of a 1988-90 750il? or the 8 series were also fitted with it..I know the E34 models never came with it


You can only find them on '88-90 750iL. 91+ came with ASC and phased out the LSD.

I have a large case 3.91 LSD from an E34 that wold be a direct fit for your car, if you are interested.

I want to stay with a 3.15, its perfectly geared for my needs.

[me78569]

Easiest car to find the 3.15s is a 88-90 750il . the 8 series had an open 3.15 and a lsd 3.46 or 3.64 I believe.

Swapping the medium case diff is a bit of a pain since the input and output flanges on the diff are different between the med and large case diffs. The hub input is also different. I think you can Frankenstein something together, but it's a lot of work if you aren't looking for more diff choices from the e36 crowd.

[strictlyJDM]

Easiest car to find the 3.15s is a 88-90 750il . the 8 series had an open 3.15 and a lsd 3.46 or 3.64 I believe.

Swapping the medium case diff is a bit of a pain since the input and output flanges on the diff are different between the med and large case diffs. The hub input is also different. I think you can Frankenstein something together, but it's a lot of work if you aren't looking for more diff choices from the e36 crowd.

yeah sounds like ill be going 88-90 750il 3.15S now

[Hoolie]

If it's the crown wheel and pinion that gave out... Find a normal pumpkin and switch in the LSD.. . Peaked in to see the extent of the meyhem?

[strictlyJDM]

If it's the crown wheel and pinion that gave out... Find a normal pumpkin and switch in the LSD.. . Peaked in to see the extent of the meyhem?

Yeah, i plan on taking it out first, disassemble and see if I can swap it out from another diff

[RVAE34]

Just curious why you think the diff blew up? Are you sure you didn't just lose your CSB and are hearing the DS smacking around? I find it hard to believe you destroyed a diff just moving the car.

[Sneezy]

Just curious why you think the diff blew up? Are you sure you didn't just lose your CSB and are hearing the DS smacking around? I find it hard to believe you destroyed a diff just moving the car.

Agreed, unless we are missing part of the story...

[strictlyJDM]

Just curious why you think the diff blew up? Are you sure you didn't just lose your CSB and are hearing the DS smacking around? I find it hard to believe you destroyed a diff just moving the car.

i wasn't being completely serious when I said that, obviously moving my car would not explode my diff.

I plan on taking it out this weekend and seeing what exactly happened, hopefully a "easy" fix

[ArnZ]

Maybe broken front diff bolt?

[RVAE34]

i wasn't being completely serious when I said that, obviously moving my car would not explode my diff.

I plan on taking it out this weekend and seeing what exactly happened, hopefully a "easy" fix

Either way, I still find it hard to believe you destroyed a diff on a stock car. Much more likely it's a number of other things. Flex plate/guibo, CSB, diff mount, CV axle etc.

[strictlyJDM]

Either way, I still find it hard to believe you destroyed a diff on a stock car. Much more likely it's a number of other things. Flex plate/guibo, CSB, diff mount, CV axle etc.

you can only imagine how shocked I am...I never destroyed any differentials in any of my cars...I do all sorts of motorsports also...track days/auto-x/drifting

and right when I moved my car, clunk and i already knew something went out.

Funny because when I parked my car there couple days ago, nothing was wrong with my car. It's like it broke overnight..but I believe something was worn inside the diff already as there was small chatter when turning really tight.

[PorscheH6]

Do you leave your car keys in plain sight? :shifty

[RVAE34]

Check the wheel bearing as well if you heard noise when turning.

[T444E]

3.15s came in the 750 sport models. The stock diff from a 540 was with a 2.81 or a 2.93 (both open diffs). The large case diff is what you need. You can't pull a diff from a 530 or 525 or 535 as a direct bolt on. You are limited to either 7 series diff, stock 540 or m5 diff and 8 series diffs as far as factory replacements.

Sport model? Wat.
They were an option on all early 750iLs, Cold Weather Package had it included.

[strictlyJDM]

Check the wheel bearing as well if you heard noise when turning.

Good call, wheel bearings are fine, checked them out already. The sound was definitely coming from the diff. It just sounded like clutch type LSD chatter. Ill report back with what went wrong as soon as I get the diff out..

[me78569]

Sport model? Wat.
They were an option on all early 750iLs, Cold Weather Package had it included.


Meant 88-90 750ils

[strictlyJDM]

okay with further investigation...it seems like its NOT the diff and something in the driveline. I am pretty sure something failed with the driveshaft...

what components are bound to fail on the drive shaft?

[ArnZ]

Center bearing or guibo. Both very common to give out.

[TGreene]

Or the U-Joint.

[RVAE34]

Not likely though ^ Most likely the csb or flex plate/guibo. Seems there are a lot of threads on driveline vibration recently. Going to replace my guibo next.

[strictlyJDM]

UPDATE - after finally getting the car up in the air, it is a broken diff bracket

http://forums.bimmerforums.com/forum/showthread.php?t=1803312&highlight=broken+front+diff+bolt

exactly like in the thread above

[ArnZ]

nice one. i had my strengthened, ill get around to uploading pics later tonight

[strictlyJDM]

nice one. i had my strengthened, ill get around to uploading pics later tonight

where did you order the part from??? its a 420 dollar part from pelican parts..i would like to avoid that if possible. Might have to go the pick n pull route.

do you also have the part #?