I realized as I was driving home from a recent car show (first time I've driven the car since September) that I have developed a significant driveline vibration in the camaro. Here is some background:

1991 Z28
LS1
T56
Stock driveshaft
Stock Rearend

Vibration happens only when on the gas (most noticable cruising at highway speeds). Take foot of the gas and the vibration goes away.

All I can think of is that I converted the T56 from a LT1 style to a LS1 style when converting to the LS1 motor. It didn't have this problem right after completing the swap, but I'm sure it's probably developed over time (I don't drive the car much).

I can't rule out anything yet, but It's unlikely to be the driveshaft or rearend since those are about the only thing left in the car that are stock and original.

Suggestions?

Did u get the driveshaft as part of the car or seperate. The only was to make sure that the driveshaft is for that tranny-rear diff combo is not have it balanced.

Befor that check ur u joints. they usually go out. I just helped a guy couple weeks ago.

Can you adjust your pinion angle? It could be at a bad angle and causing vibration under load.

The driveshaft and rearend are original to the car. the tranny was in the car prior to the LS1 swap. So effectively, the only rear changes were from the front cover/input shaft forward. I'm afraid that I left too much play in the input shaft when I swapped from the LT1 front cover to the LS1 front cover.

I will check the U-joints tonight and see how they look.