As you can see I am new to this forum so I’ll ask for your forgiveness and your help. I have a 1966 GT convertible with a four speed. The car still retains all of its original drive train parts such as the engine, transmission and rear end even though ALL have been rebuilt. We restored the car COMPLETE and to our dismay it still has a very bad clutch shutter starting off in 1st gear. After the car is moving it shifts fine from 2nd, 3rd and 4th however it does have a very fast shutter in a down shift. The same can be said in reverse gear. The car will shake just as bad as it will in 1st.

So, the history of the car, it ALWAYS had/ has this problem with numerous three fingered clutches installed until recently. I just installed a NEW diaphragm style clutch and pressure plate with a roller pilot bearing. Pressure plate was reground
on both sides checking (on the engine with a dial indicator) .002 of an inch. Checking the bell housing on the engine the I.D. is .005 T.I.R. and the face is .005 parallel.

In a desperate attempt I changed the pinion angle 2 degrees lower and there was no change to the car. This is a solid car (NO RUST) we would love to drive but not in this condition. Any help in solving this mystery will be greatly appreciated!  ?  

Welcome to the forum. This issue has come up a few times. Most folks go to the mcleod setup and make sure their  Z bar and pedal activation mechanism is in good shape. If you back to July 2008 and look you'll find a post on this subject with several recommendations.  

Thank you very much!!