Hello!

I have a 2000 silverado with the 4.8L and nv3500 transmissions. Recently put a new clutch in it and everything was working great until a few days after. Now when I release the clutch to get moving in first gear there is a "thud" coming from what sounds like the transmission. Can actually kind of feel the shifter move in my hand a bit as the motor torques up but all the mounts and bellhousing bolts under neath are tight. There is also no grinding or vibrations, and it doesn't pop out of gear. It doesn't happen all the time either. Any ideas as to what this could be?

 

Just from past experience with an older rear wheel drive car, I had a similar issue. All bolts were tight, but one of the mounts was broken. the rubber part of the mount was broken or split. dont know if this is an extended cab or not, if your truck has a double shaft check the carrier support bearing and slip joint......

 

Check all the u-joints to.