Transmission Gear Slack?
 

Turboll Transmission:
In first gear sitting still, when I dissengage the clutch I get about a 1/5 of a turn in the driveline before power is distributed to the diff. I can see this happen with the shifter boot and everything removed. Then when in motion, still in first gear at a low speed I can feather the gas and watch the driveline bounce back and fourth between accel and decel. This is enough to give me the "bucking" characteristic. I also receive the "chatter" sometimes starting in first and almost always starting in reverse.

I've had this same problem with two trannys. I've checked both front and rear u-joints. Had the diff rebuilt to specs.

I saw in the Transmission / Diff FAQ section at Post #5.
Q. Abnormal noise from transmission?
A. Probable causes:
1. Insufficient oil
2. Deterioration of oil quality
3. Worn bearing
4. Wear of sliding surfaces of counter-shaft gear
5. Wear of sliding surfaces of gears
6. Excessive gear backlash
7. Damaged gear teeth

Has anyone else ever experienced this specific problem before? If so, is it resolved with a rebuild or gear replacement?

if the driveshaft turns, but the car doesnt move, thats the diff. The guy who rebuilt it may have left excessive backlash in the ring/pinion. I set mine up pretty tight, and theres still a little slop. Cant get it all out...

When I had got the diff back from the shop I checked it for play. There was none. Unless it takes the force of the engine to expose the play in it.

so just to clarify, you see the driveshaft turning about 1/5 rotation prior to the car moving forward?

Yup.

then i would say its slop in the rear. Try holding the driveshaft in place and rotate the wheels.