How many spring washers in factory LSD?

[b*saint]

So instead of swapping back in the open diff due to lack of drivability with the "new" one, I opened up the LSD assembly. First Whoever "rebuilt" this thing is an idiot. They put the spring washers back to front. There is 4 spring washers. I know some people add washers. This thing has a LOT of lockup. I don't think the factory diff had 4 washers. For some reason I thought the factory LSD only had 2 or 3 spring washers.

Anyways its 4.44 so any spring info would be great.

Also there are 2nd set of custom ramps ground into it. I am going to use the factory set of ramps. This should be ok right?

[b*saint]

So I put two springs back in because the diff is more for winter, than for performance. Assembled the LSD unit correctly. Shimmed up the bearings correctly. It is now officially back to factory driveability. I'm never buying a "modified" diff from an unknown source again.

[FredK]

There are two Belleville washers that preload the friction discs in a factory LSD. Swapping back to the factory ramps will be fine.

[CorvallisBMW]

You can run 3 washers safely and get about 40% lockup, never tried 4 though

[b*saint]

You can run 3 washers safely and get about 40% lockup, never tried 4 though

with 4 springs, it sounded ridiculous. Ever hear an eaton locker? It was almost like that in a way. Im suprised my little axles with 250k and my driveline didnt explode.

2 washer is perfect. Its so quiet. Its like my old medium case LSD. I guess I dealt with it so long I didn't know what it was suppose to be like.

[b*saint]

So I read that if you stack the washers in the same direction it will increase the spring rate more than alternating. So since they had 2 plus 2 in the same direction it must have had a huge amount of lockup.

[Wanganstyle]

Spring washers increase preload; not lock up.
(more) Preload is designed to allow heavy (heavier) cars to have extra traction in poor conditions; i.e. a 7 series e32 at 3800lbs has a thicker set of spring washers in the LSD unit than a e30 at 2800 lbs ; This was the original manufacture intent and use of "spring washers" in the differential.


if they constricted motion to the point that no differential motion can be done anymore inside the LSD capsule then the person who set is has managed to remove the "Differential" part from the LSD. Basically set it up to be= welded.

BMW did spec 4 clutch disc LSD units in some cars with no spring washers at all; a flat spacer is in the case instead to take up space.

[b*saint]

More preload in a little car = more lockup. This diff only had 2 clutch discs.

[FredK]

More preload = more STATIC lockup.

However, whenever you're on throttle or decelerating, the pinion cross shafts exert pressure on the LS unit guts through slots cut in the spider gear housing, which pushes outwards against the clutches and steels, which in turn gives you the locking effect.

So why are the Bellevilles there? Well, when you're in a low traction situation where acceleration doesn't actually wedge the pinion cross shafts into the spider gear housing, the Bellevilles must provide the clamping force.

[b*saint]

Yes its basic physics/mechanical engineering. I know how it works. Its why this always feel locked and a helical or ratchet doesn't.

Maybe I should've said more preload = more nuts to break free this thing. My tires will prove it to you.

[Wanganstyle]

More preload = more STATIC lockup.

However, whenever you're on throttle or decelerating, the pinion cross shafts exert pressure on the LS unit guts through slots cut in the spider gear housing, which pushes outwards against the clutches and steels, which in turn gives you the locking effect.

So why are the Bellevilles there? Well, when you're in a low traction situation where acceleration doesn't actually wedge the pinion cross shafts into the spider gear housing, the Bellevilles must provide the clamping force.

the pinion cross shafts ALWAYS touch the ramps on the gear housing in 4 places at static. This is the ZF design; you can see it when stacked up.

BMW (and others) that spec the ZF LSD unit sometimes deliver it in cars with NO BELLEVILLES. At all

Alfa romeo setup has no belleville springs, the unit is designed to work well with either some or none (as long as setup properly).

One can give ZF engineering a phone call if really in doubt; BMW did ship a non-belleville spring 188mm LSD unit with 4 clutch discs and steels and a 1.5 way center section stock OEM. Some people on R3v may own these cars and not even realize it-

One could theoretically increase the static preload/lock to a level of never-unlocking. This would be like a welded / spool. Sometimes it happens to be this way when setup strangely; a spool (like a shifter kart) is actually really predictable handling.

[!kid]

this might help a little.