Okay, I bought my car like this about a month or so ago, I don't really have any idea what it is though.

When I put the car into D, it makes a thud from the back by the differential, and then the car lurches forward for a split second. Sometimes it's loud, and sometimes it's not really noticable. I've also noticed that sometimes it makes a thud when upshifting or downshifting from 1st and 2nd.

The last owner told me that it's some bushing related with the driveshaft... I dunno. What I do know is that the last owner replaced the differential at 90k with one from a car that had 60k, and currently, my car has 180k on it.

Please help, I did try searching, but didn't really come up with anything.

 

Take the car to a mechanic to have it examined. There is a driveshaft bushing which could go out as well as a tranny mount which could also cause the symptoms. Have a mechanic examine the car as well as have the tranny looked at. This problem could be a multitude of things.

 

driveshaft bushing, rear trans mount, and/or potentially the rear carrier bushing/mount

 

Okay, I'm not really sure what to make of this.. I put the car on jackstands today and put my camera under it. I went Park --> Drive --> Neutral --> Drive --> Park

http://s50.photobucket.com/albums/f3...t=MVI_1494.flv

The car got much worse today. Now below 1.5k rpm, the car shudders and jerks really bad, and over 2k rpm, I can hear the damn driveshaft or driveshaft coupling hitting something (probably the body).

 

That really does not sound too good. Aside from the driveshaft bushings being worn, sounds like you have multiple problems going on there. RPM range should have very little to do with the car jerking really badly. Which end is the noise coming from, the tranny or the differential. If from the tranny, you may be due for some serious tranny work. If from the differential, sounds like something is locking up and you are trying to force it to move. Sorry to break it to you, but it sounds like an expensive fix. I am not an expert, and I know PD will chime in since he is so knowledgeable, but this is just my 2 cents worth,

 

have ur mech check these out:

-rear transmission mount.
-driveshaft bushing
-rear axle carrier bushings
-check the diff mounts for damage/play/looseness

 

Just an update...

I replaced my whole driveshaft in early June because it ended up cheaper just to buy one out of a car with 102k miles than changing out the joint. It made a huge difference, since the joint on the old one was totally shot.

The car still shifts rough and I think the transmission is still moving under heavy acceleration. I daily drove the car for over 3k miles with no problem after replacing the driveshaft, so it's fine under normal acceleration. I've experienced the same problems on my friend's LT1 T/A, and it turned out to be the trans mounts... so that's my next plan of action while the car is in storage. Does anyone have any how-to's on how to do this?

Also, when I changed my rims, I noticed that when the car was in neutral, the wheels off the ground and the parking brake off, the rear wheels spin only so much in one direction and then just stop and won't move with my own strength. Is this normal or is it a sign there's something going wrong with the diff?

 

il have a rear trans mount tutorial up soon