I have a 1990 Toyota 4wd, 4cyl, Manual. I have this loud noise under my truck somewere from my trans to rearend. It sounds like a knocking noise when i start in 1st gear through 2nd. It gets faster with speed. It does it in 2wd and 4wd. I put it up on blocks and ran it through the gears while I was underneath but it did not make any noise. Put it back on the ground and makes the same noise. It has a new clutch assembly and new diffs. It made that noise before the clutch and diffs. Any Ideas?

 

T-case mount and/or u-joints?

 

They look fine. No excess movement but looks can be deceiving.