Clunk noise when shifting upwards

Dartnut said

The clunking noise you are experiencing is from a bad u-joint or joints or rear end slop is excessive.
They didn't do this when new, so why now?
Your question will be answered when you check both out compared to factory specs.
I'll bet it's a bit of both.

Click to expand...

You might be correct on something being worn but I have seen a few do it right from the factory when things were tight. One I remember real well is back in the early 80's a buddy of mine had a 78 Diplomat that did it. It also engaged into reverse hard. My only guesses are the pressure regulator got cranked up too high, and/or the accumulator spring was broken or left out. Something else that I already mentioned is if it has a shift improver kit installed a clunk like that can happen because even a tight drivetrain has a little slop in it. If the trans shifts real firm into 2nd and it happens right when he lets off the gas that little bit of slop can sure make a heck of a clunk. The OP doesn't seem to know if it has a shift kit or not by what I read.

Just my .02