When I accelerate hard in first gear I hear and feel a slight sound kind of like marbles crushing against each other. Any ideas out there? First I thought it might be the U-Joint on the drive-line. The transmission has about 5000 miles on a rebuild, so that is why I doubted it was the transmission. I don't seem to feel or hear the noise in 2nd, 3rd or 4th gear. I do not have any problems shifting between gears.

1968 427 w/M-21 Transmission

Any ideas?

Mark

Perhaps a U-joint, either on main shaft or half shaft...

Without noise in the other gears, it really points at first gear. The only other thing that could only make noise in first it the torque applied. You get more torque in first. Now the question is, is it on hard acelleration, or just in first in general?
If it's on hard acell, look at other drive line components. If it is in mid range acell but only in first it is indeed the trans.

I talked to a local friend and he said the clutch could be the problem. Possible warped pressure plate. I'm not sure. I can feel the chatter on the shift handle. It is only for a very short time. Does this make sense to anyone about the clutch? I've only been pushing it moderately hard. Haven't been dropping the clutch at high rpm's.

Mark

A clutch usually does not chatter when fully engauged, unless it's slipping. And that would be consistant in all gears. I don't think it's the clutch.

2 solutions,1 don't use 1st gear,2 crank the stereo up full blast,and drive it like you stole it.