SM 465 clunking

[mountainexplorer]

At idle and not moving, the SM465 4-spd in my Suburban makes a clunking (almost a knocking) noise. It is less noticeable when the clutch is engaged and not noticeable at all when driving. What could it be?

I already pulled a motor out because of the noise (thinking it was knocking), and now I found out it's in the tranny somewhere.(doing the exact same noise with a new motor).

 

[mudhog]

when you pulled out the motor did you put a new clutch in?

 

[wrathORC]

Yank the trans and look at the input shaft bearing and race. You'll probably find that there is a lot of chrome missing off both. While I was in there I'd replace the seals at both ends and check the output shaft bearing and race. I might even convince myself in to buying a couple new synchronizers.

 

[TXsizeK5]

This happened to me also...
after romping one time i was sitting in a parking lot and had it in neutral and let off the clutch pedal and there was a *knock knock knock knock* type noise and i was like wtf... but the next day I checked it out and it was cool... somone told me it could be the flywheel. I have no idea =X

 

[mountainexplorer]

The clutch was a used one that I had recently put in my other truck. It was still in good shape.
Once in a while the shifter jams in 3rd, and sometimes on a quick shift, it grinds between 3rd and 4th. It also sat half uncovered for about 6 months. When I put it in the Suburban, I drained out quite a bit of water and added new 90W gear lube.
It also sounds like my tranny-Tcase coupler sleeve has some play in the splines. I just don't want to pull the thing out, since I just put the whole thing together, but maybe I'll have to.