He's right about the Dot5, I assume you rebuilt the system before you used it. Anyway U joints clunk pretty good loose and by then they make noise and vibrate too most of the time. I am leaning to the above post also motor mounts. Put a block of wood under the oil pan and a jack. Don't try and lift the car! Just start to unload the suspension, see if you dont have a broken mount or mounts.

 

is it a brass button clutch?



Looking at your post i think it is.



Brass button will shudder when they have been glazed/slipped. Or when you are riding it too much.



If your not doing the above, once you have fully released the clutch does the shudder continue or does it stop?

 

It stops once I release on mine. The shutter happens when the power is transfered. After that, riding smooth. If that makes sense...

 

Hey I am pretty sure I know the fix, one guy touched on it with the brace but that's extra weight. My 87 n/a I just started dealing with the same problem, not as severe but hot sometimes had to feather the clutch out. Fresh clutch as I just put the car together. Anyway I had the car on my lift (yeah I have a lift) and tranny mounts were sagging. Well found this site www.banzai-racing.com ordered up the poly mount set motor and tranny. Talk about a change of attitude! The mounts are supposed to soften a bit and it's pretty solid right now, so I hope they do. It's amazing how much more power the car is putting down right away and it shifts better. Before it felt notchy and slow to up shift and drop a gear. I switched to synthetic in the tranny and rear two weeks ago. I built this car for mileage so it's running the 3.91 lsd out of the auto car and I started turning tires pulling off a corner! Took it out and drove it like I stole it, clutch works great! Buy the way it's getting 20 mpg to and from work 87 pump and hope to see 26 true hwy.

 

Give it a couple hard launches. Your clutch could be beginning to glaze as someone suggested.



Was there any evidence of a leaky rear main seal?