ARRRGGG - differentials madness!!

[HausBimmer]

OK, I am complicating this by trying to do a double swap. New LS for my 89 535i 5 speed and the 3.46 from my 535i into a '92 525i we are converting to manual trans. I punted e32 diff. in the first junkyard (last weeks post) and ordered an e32 3.91 LS online. Hmm, won't fit the 105mm - 10mm bolt hubs on the 92 525i donor car driveshaft (so even e32's w/ 3.5 engines in auto had the smaller hub). Went to a different junkyard in KY today and got a nice 3.73 LS from an '89 525i (M20) 5 speed. Guess what, also the small hub - came back here and read that people were bolting the 3.91's from auto's directly onto the 535i manuals. --SOOO-- It seems like pre-M50, everything was small hub? This kind of suck because I still won't have a large hub diff. to put in the 525i tranny conversion car unless I go buy another diff, just to get the stinkin' hub. Any other idea? Anyone make a Frankenstein driveshaft by putting the manual front on an auto rear by replacing the u-joint?

[tfritz]

If I am not mistaken (which I may be) but I was thinking on any small case differential LSD you could swap any of the input or output hubs from any other small case LSD. The output hubs being easy to swap and the input hub more technical and difficult but can be done. Somebody else chime in...

[attack eagle]

true. but all rear shafts are the same length so yes, you can Frankenstein a driveshaft with an auto rear shaft and a manual frontshaft.
IN my m50 shafts, they both had a single 19mm bolt hidden in the u joint that holds the two halves together. Recommend balancing it before use.

I think shrike has a franken-shaft as he swapped the input flange on the diff instead of finding a rear 1/2.

[tfritz]

yes I was thinking to hard, it would just easier to swap driveshaft halves, although it was a pain in the ass to get that "hidden" bolt out of my driveshaft but im sure a lot easier than swapping diff. parts.

[HausBimmer]

Hmm, the hidden bolt thing is the kind of tip I was looking 4, thanks. It seems that many of the desirable ratios came on the pre-M50 diffs - and now it looks (from my limited search) that theses are all likely to be small hub (whether manual or automatic). The driveshaft trick looks like it is worth trying and there is a place in town that will balance them - but said they don't have metric tubing to build or mod them. I give an update on the Franenshaft.