I'll give you all alittle history on my 84 z28 H.O. to maybe help matters somewhat. I restored it over a 2 year period from front to back and did some up grades on the h.o. 305, nothing super radical. The trans is the origional 700r4 and the car has 3.73 in the rear. We decided to rebuild and upgrade the trans beings it was out, but really needed nothing. We put heavy duty clutch pack in it, transgo shift kit with servo and new pump ect, everything. The car go's good and quick shifts hard when you row through the gears. The only thing I didnt rebuild was the rear end, it looks pretty good, tho I did clean it out and put new rear end fluid in it. Question now is when I launch and go through the gears and after its done and said and back off the gasser why would I get a mild clunk for say as the car slows down and automatically drops into the next gear? Im not sweatin over it and am not afraid of replacing or fixing, cost isnt an issue. The car has always done this and its been done for a year now, I take it on the interstate and drive 65 pluse in overdrive right to alittle getting on it and going through the gears. Nothing seems hurt tho. I've also got all new poly bushing's for the trans mount, torque arm and motor mounts, pluss new bolts and nuts for the rear torque arm to rearend mounting. Anyone who has a good educated guess to kill my curiosity? Thanks. The clunk is only from 1st to 3rd, but not in drive/overdrive.