Hey guys. Wanted some opinions on this problem since it has me a bit concerned.

Whenever I shift gears up or down, a clunk/knock can be heard from somewhere under the car. Almost sounds like It's coming from the driveshaft/tailhousing area. It does not do this EVERY time I change gears, but I'd say about maybe 8 out of every 10 times it makes this noise.

A little more info, is that this noise was not apparent before I had the transmission converted to full manual valvebody, and I think I understand why. If you shift up/down with your foot on the gas, it makes either a very muffled sound or no sound at all. It is only when you downshift to engine brake with your foot OFF the gas, or upshift with your foot off the gas that this sound becomes grotesquely apparent. When the transmission was still automatically shifting before the valvebody conversion, I could hear the very muffled version during shifts but it was never the prominent knock/clunk sound I hear now because all shifting took place automatically when I was busy accelerating and I would never engine brake before now. I want to say that a couple times I did engine brake before the rebuild to get a feel for manual control of the gears, but I don't explicitly remember if the noise was there before.

The transmission does NOT make any abnormal noises when cycling through the gears at a standstill so I highly doubt It's anything internal. My transmission mount is fine and the crossmember is rock solid. I do NOT get a clunk if I lift my foot off the gas and then lay back into it. Only during a gear change.

Would you guys take the same guess I am and say It's the U-Joints, or is it most likely something else?

 

my car did the same thing whenever i accelerated hard. but never had it when shiftin probly cuz my auto slips back so shifts arent hard but it was a bad tranny mount. got new one and problem was gone