Bad Thump in Drivetrain "Not The Driveshaft"

[DrGonzo]

For the longest time now I have had a really bad thump in the drivetrain that usually occurs when I'm in a gear and give it gas. The issue is too much slack in the drivetrain and when I give it gas it will thump bad until the slack is taken up.

I initially though it was the driveshaft for two reasons, Every thread about drivetrain thump gets directed to Bad Carrier bearings and I had a lot of slack in my driveshaft.

I swapped out the driveshaft with another and still the same issue, I swapped out the read diff and still the SAME ISSUE!!!!

So I checked the Driveshaft again and even the used replacement had a lot of up/down - side/side play. Well I was not going to drop almost $200.00 on new carrier bearings as I was still not convinced it was the carrier bearings caused the thumping. So I took my spare driveshaft and willed in the carrier bearing doughnut with polyurethane. Let it setup for about a week and re-installed it. There is ZERO play in the driveshaft now but I can twist it almost two inches either direct.

Why is there so much slack in the driveshaft? This slack is what is giving me the damn thumping and I don't know how to alleviate it. Any Ideas??

[futurevr4man]

Check your motor mounts

[DrGonzo]

Check your motor mounts

There Solids......

[Chris GTO TT]

Output shaft stripped

[DrGonzo]

Here's pics of the output shaft I took in Nov 2011. Car had pretty much been sitting since then as I didn't drive it much in the winter.

[DocWalt]

T-case slop or tranny internals then.

[Nihil]

You try adjusting rear diff backlash? That's on my to do list...there's an informative thread on the other site...

[DrGonzo]

You try adjusting rear diff backlash? That's on my to do list...there's an informative thread on the other site...

Got the URL for that thread? All the ones I have read don't have any decent details on it. Manual is pretty shady about the procedure also.

[Nihil]

I hate linkin to the other site ha but yeahhhh....here ya gooooo Adjusted Rear Diff Backlash, some hints - 3000GT/Stealth International Message Center

[Jimvr4]

It's pretty easy to measure the backlash and see if you have a problem. I had a leak at the pinion seal and ended up measuring BL just to make sure everything was OK. I just needed a new seal as the old one was worn out.