My 1997 T100 4x4 just started making a grinding noise that sounds like its coming from below the bed right behind the cab. It's worst when around 45mph in 4th I let off the gas, it sounds like a loose grinding sound, kind of high pitched.

I was reading something about the carrier bearing in between the driveshafts, would that be making the noise? How do you check that without a lift (or a garage, with 8" of snow on the ground)?

Thanks

probably an axle bearing, you can put the truck on a lift and have somebody listen to the axles while its spinning in gear, be careful though...

If it is an axle bearing, do a hard left / right while at 30-40 mph. A bad bearing will sound off under load and not when unloaded.

If it is an axle bearing, do a hard left / right while at 30-40 mph. A bad carrier bearing will sound off under load and not when unloaded. Another possibility is the rear end itself. Check your gear oil for metallic paticles and see if there is excessive play in the pinion / ring lash.

And the carrier bearing WS refers to is in the differential. The carrier bearing you cited in your original post is usually called the center bearing.

I had a bad center bearing replaced that I never noticed til the driveline shop called to say they couldn't balance the shaft because that piece was shot. It seems by what most folks here report that the outer axle bearings and ujoint closest to the pinion are the ones to go out first, pinion bearing the next most popular offender, and the center bearing quietly goes somewhere in the middle along the line, but every post I've read about the center bearing here has had a "wth, I never noticed it" kind of reaction.

hey, just read your problem on your 1997 T100, 4x4, x cab problem. I think I have the sme problem w/ my 1997 T100, 4x4, X cab and 205,000 miles on it.

Can you tell me what was the problem and what was done to fix it.
Thanks a lot!!! wawsee

This problem can't be a wheel bearing since it changes sounds between power and compression. Wheel bearings, axle bearings will be constant. Since it's there all the time but is worse when on compression, it won't be a differential pinion bearing because the problem is related to forward and reverse thrust. My best guess would be the center carrier bearing on you drive line. It's possible that the bearing is going bad and the noise is worst because the dust shield is rubbing against the bearing housing on compression which pushes the drive line forward.

Make a mistake. I meant the drive line pulls back. Pushes forward on power.