Rattle? ....but not steering shaft?

[Hutch]

I have an '02 2500HD with the 8.1/Allison combo and 3,500 miles.  I can feel AND hear something rattling underneath.  I can feel it through the gas pedal and through the floor when accelerating and driving over a rough spot in the road.  It does not happen when accelerating on a smooth surface and it doesn't seem to happen when I'm going over a rough spot but NOT accelerating.  That makes me wonder if torque is causing something to move just enough to rattle against something else.  I originally thought it might be the leaf springs rattling so I wrapped the loose ends of the leaf springs with pipe insulation and that didn't help so I don't think that's it.  I don't think this is the steering shaft problem (?).

 

Any ideas?

 

Thanks,

Hutch

[CMNTMXR81]

Chassis wise, Broken trans mount/broken motor mounts, torsion bars.

 

More severe, a bad torque converter and the possibility of the flywheel being loose (which is a problem with a few 8.1's and Duramax's with the Allison).

[David Thomas]

Can you elaborate on the flywheel/torque converter problem?  Anyone on the forum that's had this problem and could describe it's symptoms?

 

Thanks,

 

David Thomas