I have 86 Camaro with 700R4, 350 after market, I drive it about 1 time every 2 to 3 weeks, no air to hot during summer. Drove it for about 15 minutes to get the temp up. Stopped and brought the RPM up to about 1500 on the converter, stock, and and flored it. Normally it will spin both tires for about 6 to 8 feet, never any hop, this time the car shook really bad and did not move more than a couple of feet. I lifted as soon as I could. The car drove fine afterwards, however I have NOT tried to launch again since this happened. Trans mount and torque arm bushing looks fine. I have brought the rpm up to about 2000 on the converter, sounds fine.
Could this shudder have been caused by the POSI unit??, Can the posi unit be rebuilt?

Any thing else that could have cause this shudder??

 

If everything seems fine, I would try it again and have someone watch what happens. It could have been just really bad wheel hop. Before I boxed my control arms in, my car would wheel hop bad. It felt the car was self destructing.

 

I agree with "built", sounds like really bad wheel hop.

Dan