Car goes in gear, let off clutch, car doesn't move, but car doesn't stall????

[karimnassef]

I have a 99 vert m3 5 speed. The other day my buddy and I were out drifting and he clutch kicked and a quiet but kind of loud clunk happened and the car stops moving. I let out the clutch and give it gas while its engaged in any gear and it doesn't move. I checked under the car today and found the driveshaft to be in one piece and not broken, but an interesting thing I found was that I had the left rear tire lifted up while my right side was on the ground, and I put the car I gear and only the left side spun. Im pretty sure since its LSD both tired would spin, but since one is the air, and one is on the ground, the car should stall when I let out the clutch, but it stayed on, and the lifted side kept spinning. Another interesting finding I found was #16 in this diagram https://www.realoem.com/bmw/enUS/sho...diagId=33_0371
that bolt was snapped and my diff was freely moving up and down. Any ideas as to whats this bolts purpose? But overall im not sure why my car doesn't move, my clutch is good, my driveshaft is good, my axles are good, could it be my diff? (even when 1 tire is still spinning).

[NeilM]

The E36 M3 vert doesn't have the most rigid chassis, even by the standards of the time, and isn't well suited for drifting.

Bolt #16 is one of the three that secure the diff to the rear subframe. It goes through a rubber bushing that's pressed into the subframe and then threads into the diff housing. When one of the diff bolts breaks from abuse, it's that one. A contributing cause is often deterioration of that bushing, especially if it's the two decade old original, allowing too much movement and over stressing the bolt.

If you're lucky you have no drive only because one rear wheel is lifting and spinning (despite the LSD) — is that the case? if so replacing that bolt will fix it. This may not be as simple as it sounds at first, since the snapped-off bolt shank needs to be extracted from its threaded hole in the diff case. That may in turn require pulling the diff from the car. Be sure also to replace the bushing. Not to would be a false economy at this point. It does need to be pressed out of and back into the subframe using the proper tool.

If you're not lucky and have broken something else like the diff internals, then that's another thing entirely.

Neil

[TostitoBandito]

If you're considering drifting one of these at a minimum you need to put a bigger front diff bolt in along with stiff/solid bushings basically everywhere you can. Otherwise you're gonna break stuff like this when things try to move under extreme load. There's also diff reinforcement braces which bolt into the subframe and take some additional stress off the front bolt. Check out the drifting subforum here for more specifics and builds.

[Solaris99]

Let the clutch out in gear while somebody else looks under the car (with the e-brake on and they don't cross the path of the wheels while looking, for safety) at the diff input flange to see if the driveshaft is spinning. That'll at least give you an idea of why the car doesn't move while it's in gear.

[ProAutoRC]

Like the others have said, put the car on jack stands or a lift if you have a buddy with a shop, if when you put it into gear you can visibly see the driveshaft spinning, than you know it’s not in the trans or clutch system. It’s a problem inside of the differential. If you are saying you can move the pinion up and down, than you know at this point, you have wiped the pinion inner and outer bearings at the least. Probably have done more internal damage. If the bolt snapped that holds the yoke in than you must have REAAALLLYY strained the DIFF. And yess both should spin if you are running possi or LSD!! Yank the diff out and take a look!