Educate me on Limited Slip Differential Wear

[yinzerinmass]

I'm trying to gather some info on what possibly may be this winter's project.

I have a 2000 M roadster and want to assess the function of the Limited Slip Differential. How would I go about doing this. When the wheels are off the ground they do spin in opposite directions (historically i have heard this meant that the diff is essentially open). I have also read somewhere on this forum that may not entirely be the case.

I'm looking for those of you who have rebuilt failed BMW limited slips, can this be assessed somehow externally with diagnostic testing?

My plan was to call around to my go to shops and see if they would be willing to restore with a Thayer motorsport kit with the differential I brought to them, I think taking the guts out of there might be out of my wheelhouse

Thanks!

[bluptgm3]

It is likely that the Z3 came with a non-clutch style Torsen differential, which behaves differently.
Though, I see you have a 2000 ‘M’ Roadster that has a clutch pack.

Secure the car (chocks), Jack one rear wheel, place on JS, apply a torque wrench to the off-the-ground wheel lug nut. The www.newTIS.info specifies a minimum ‘break away’ torque value.


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[BimmerBreaker]

M roadsters came with clutch type LSD's - Torsens came on the non-M's in the later years.

OP I think there better things to spend your money on especially if it isnt even showing symptoms

[rf900rkw]

The M Roadster uses an M-Sport clutch type diff that is different than the typical BMW clutch-type in clutch plates, ramp angles and preload. As such it is quite easy to turn static making you think it's an open diff, or slam worn out. As long as your power-on transitions in and out of the church-lot doughnuts are smooth and controllable, I'd leave it be.

[yinzerinmass]

Thanks so much for the expertise, I appreciate it as always. I do about two autocross events a month and its definitely smooth during full power out of turns, (and no corner workers have mentioned I'm lighting up the inside wheel, as one friend pointed out to me when i used to run my E46 325)

[cpallenjr]

The VIN decoder reports that my 1996 1.9L Z3 has an option 209 Limited Slip Differential (25%). Is that a Torsen type? What kind of oil should be used to service it?

[lelandr]

M roadsters came with clutch type LSD's - Torsens came on the non-M's in the later years.

OP I think there better things to spend your money on especially if it isnt even showing symptoms

Huh, Don Fields told me that he thought that very likely my 2000 MCoupe would have one of the Torsen units. How does one verify this? I do have to do the diff bushings, so I suppose that I could pop the cover off.

If, in fact, mine has a clutch type, then it's finished. Spinning one wheel doesn't spin the other. Spinning both wheels with the input flange, only takes slight pressure from an index finger to stop it spinning.

Thanks! You're like the Wiki of Z3s.

[solimans]

I’ve also been told that the m’s have the clutch types. The non-m’s are open or Torsen in later years.

I have a torsen...off the ground when you spin one wheel the other turns in the opposite direction

Give Diffsonline.com a call...they will get you sorted

The disadvantage of a torsen is that it turns to open when one wheel leaves the ground. The advantage is that you don’t have to replace clutches every five years...


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[BimmerBreaker]

Huh, Don Fields told me that he thought that very likely my 2000 MCoupe would have one of the Torsen units. How does one verify this? I do have to do the diff bushings, so I suppose that I could pop the cover off.

If, in fact, mine has a clutch type, then it's finished. Spinning one wheel doesn't spin the other. Spinning both wheels with the input flange, only takes slight pressure from an index finger to stop it spinning.

Thanks! You're like the Wiki of Z3s.

To the best of my knowledge the M's got clutch LSDs the whole production run. Torsens were a non-M only thing

Take the cover off and look inside. Clutch LSDs and Torsens look different internally. Or remove the speed sensor and fish a borescope in there...

[Muzz258]

A picture will help in identifying the type of diff you have. Try this one.