Well not too long after my LS7 flywheel and clutch swap I have been experiencing a very loud griding (sounds like you missed a shift from idle to 1st) when I shift above 2500 RPM's.

Also, while driving above 25 MPH and I put the clutch in to give a few revs it sounds like a bad rattle in the bell housing.

I do have 100K on the tranny now, and the car has about 450-500 HP. I am thinking about just having it rebuilt.

What do you guys think it is?

 

Start by changing the fluid, and use GM Dextron III, not synthetic anything. If that does not fix it, the synchros are toast.

 

Yeah it sounds pretty bad. I think it could be the synchros. I am thinking I may just take this time to get a properly built tranny from T56 rebuilds...

Any other suggestions?