1999 JGC Tranny Noise

My 99 Grand Cherokee started making a noise that litteraly sounds like a hamster wheel spinning and rattling. It starts up in the 40 to 50 mph range and continues on up. It sounds like its coming from the tranny or transfer case. It does it regardless of whether I'm accelerating hard or cruising. It continues if I slip the tranny into neutral and coast. It doesnt change frequency when I shut overdrive off, which leads me to believe it's either in the tranny output or the transfer case, maybe a u-joint going bad?

Im getting the same problem.. mine is around 50 - 60mph.. If you find the problem reply back asap.. Im still under a Bumper to Bumper Warrenty.

You can check the condition of the driveshaft U-joints easily enough by looking under the vehicle around the skid-plate (if equipped) and cross-member - maybe a strap is loose. Use a flash-light. If you have the ball & socket style CV joint front driveshaft it could be coming from the joint - otherwise I would probably check the trans & T-case fluid levels.