74 Duster Vibration on hard shift

Hi all... I did do some searching prior to me starting a thread, but I didn't see anything quite like the problem I am having.

I have a 74 Duster, Automatic, 318, 4bbl, headers. When I bought the car the guy said it has a 2500 stall converter in the trans.

When I put the car in drive and take it easy, it can go up to top speed, no vibrations at all.

If I put the car in drive, and hammer it, when it shifts from first to second gear it vibrates from the rear of the car badly. Either center or rear of the car. Vibrates enough so that you let out of it because I don't want to break it-- whatever "it" is.

Any ideas?

Author: admin