I took my car down the road today for the first time after building it. I have regular radials on the back for now. It also has an auburn posi in it.

1rst gear was useless,,spin ,spin spin
2nd gear had a violent side to side movement untill I let off and got back in it again, it was spinning while it was doing this.

The best way to describe this is to say that someone was at the back side of the car and was shakin it as hard as they could from side to side..

What the hell is doing this? It did it 3 times!!!!!

 

help me????

Could it be the lca flexing and stock bushings??

 

It could be a lot of things. I would say it is most probably the motor or transmission mounts. It could also be that the drive shaft is way out of wack. Meaning that the driveshaft is not balanced or is bent.

 

new motor and transmission mounts,
only does this under hard acceleration, no other time

 

surely someone else had this problem before????

 

back up top..

 

It could be that there is something wrong with your torque arm, is damaged, missing or modified. Mine used to do this on my th350 tranny in my 1982 Z-28. But it was not violent and only occured when i was coasting, engine braking in second going 20 mph. I fixed it by building braces that loosely bolted from the body to the torque arm.

 

Go to the back tires of your and push on the quarter pannel. Does the car body move side to side while the tires stay in place? Mine had this problem, I replaced the LCA's, panhard, and rear sway bar bushing with poly parts, and no more problem.

 

no, the axle moves with the body.. there is some tire flex but that's it..

 

it has sfc too!!!!!!

 

Might be kinda off but what about your diff? Is it working properly and locking both tires together? might be jacked up and is alternating power left and right....

 

Could be wheel hop, mine used to on the 1-2 shift.

 

My car used to do that, when it had a 400 in it... LCA relocation brackets and LCAs finally fixed it. The car had SFCs and a Spohn torque arm, neither of which affected it much. It was so bad that people would ask me if I was doing it myself with the steering wheel. I could hold the wheel still & stand on the gas, and feel the rear end swinging itself from side to side. It did it both with a on-wheel-peel and a posi.