Busted LSD

[OTT]

Awhile back I broke my small case lsd. I needed the car back on the road so I put in an open small. I just got around to inspecting it and found that my spider gears were in a pile at the bottom of my diff case... I think the clutch packs locked, stressing the spider gears that eventually gave but I haven't taken the LSD apart to know for sure.

Does anyone know if open diff spiders will fit in an lsd? I'd like to just get a new set of clutch packs and gears if possible... if not does anyone have a LSD unit for sale?

[SkiFree]

Spider gears between the small open and small lsd are not interchangeable.

You're reasoning behind the failure is sound, a locked clutch plate means you got essentially a fully-locked diff with all that stress going straight to the gears. It'd be interesting to crack the case and see what caused the perma-lock.

BMW still lists LSD components for the E21 small case, but I believe the clutch plates and dog-eared plates have a different ID between the E21 and E30 (will varify with my notes tomorrow).

[OTT]

Maybe I can order e21 gears and porsche clutch packs... maybe.

[SpeicherBimmer]

how did you figure that out? This is Patrick, BTW

[Wanganstyle]

the small case LSD units usually shear the left side bearing surface. remove the side caps (4 bolts) and drop out the center unit to see the carnage

[OTT]

I'll post pictures

[SkiFree]

Maybe I can order e21 gears and porsche clutch packs... maybe.

The number of teeth on the friction plate are different from E21 to E30. The spider gear that the out-put flange slides into on the E21 has a shorter neck for the clutches to slide onto.

EDIT: as a side note could you snap a picture of the pumpkin top cover for me?

[TobyB]

However, you CAN stick an E21 carrier into an E30 small case...

...you'll just (probably) lose your speedo.

t

[Eric]

Why not source a medium case LSD?

[OTT]

They're all like 500€ over here and a med case is to heavy to ship APO... Any ideas? I need a 3.15-3.45.