Im looking on differentials on ebay, rebuilt one. Theres this guy sb06ca whos store is Metrix Motorsport (anyone ever order something of them or heard about them?) They sell several different differentials, mostly limited slip and for older models (E30, E34) and of course a bunch for the E36 :shifty
He states that he can configure these to fit various cars. For instance, he can modify the E34 M5 differential to fit the M3 for an additional $500.

I am looking to buy a 3.91 LSD w/ 40% Lock for $1200. Does what this guy say sound legit? Hes got a good score and everything.

Is it possible to configure a diff. for one car to fit another?

Go to the Metric Mechanics web site and look the diffs. BMW made 3 different sizes, small, med, large. Within those sizes there are several different variations. There is some interchangability, some will fit with no mods.

You did not clarify what car you're working with here. Your signature suggests it might be an E39 528i.....

The variations on BMW differentials are mind boggling even within a single series (E39). Do NOT assume that diffierentials can be swapped between different vintages/series unless you have specific information proving it. Since you're in the E39 forum, I'll tell you with high confidence that non-E39 diffs will NOT fit.

The size of the ring gear and differential carrier is only one issue. For example, the beefy E38 posi unit uses the same carrier & ring gear size as an E39 M5, but it these diffs will not fit in E39. It does not fit because the E38 and E39 suspension and subframe design is not shared.

1) cases are shaped differently to allow mounting on a specific subframe
2) length & size of the pinion varies and this affects driveshafts.
3) size and positioning of the output splines & carrier side bearings have an impact on half shaft type and length.
4) rear cover bolt pattern and shape varies
5) the rear cover is specific and used as a subframe mounting adapter

You did not clarify what car you're working with here. Your signature suggests it might be an E39 528i.....

The variations on BMW differentials are mind boggling even within a single series (E39). Do NOT assume that diffierentials can be swapped between different vintages/series unless you have specific information proving it. Since you're in the E39 forum, I'll tell you with high confidence that non-E39 diffs will NOT fit.

The size of the ring gear and differential carrier is only one issue. For example, the beefy E38 posi unit uses the same carrier & ring gear size as an E39 M5, but it these diffs will not fit in E39. It does not fit because the E38 and E39 suspension and subframe design is not shared.

1) cases are shaped differently to allow mounting on a specific subframe
2) length & size of the pinion varies and this affects driveshafts.
3) size and positioning of the output splines & carrier side bearings have an impact on half shaft type and length.
4) rear cover bolt pattern and shape varies
5) the rear cover is specific and used as a subframe mounting adapter

I am not gonna try to put a regular differential from another model in my E39. The shop that is selling these say they are going to configure (for some extra cash) it to fit the E39. I am asking if it is possible to do this, or are they lying out of their ass?

I'd be leery myself. Why not just get an LSD thats made for your car specifically instead of having someone "configure" one for it? I just ordered a Quaife for my BMW brand new for $900. Does this place offer any sort of warranty on these diffs they sell? Are they new or used for that price?

Not trying to sound all negative, just playing devils advocate =)

-Brad

yes but he wants an lsd, you cant get an lsd for 900 or even 2000 dollars for the e39. I dont see why one couldnt be modified to work, its not rocket science.

List on a quaife is $1200, if he has a hookup at a shop he can get it as low as $900 (granted, this is a straightline diff, and probably an OK road racing diff).