Cyclic noise coming from drivetrain...

[ZeroOne]

Ok, before I start tearing stuff down, I'm just wondering if any of you guys would know off the top of your head what this noise is. It sounds like it might be expensive, whatever the hell it is.

A little background, I had 4.56 gears installed last June. "Something" happened, and the pinion wasn't tight, possibly because the pinion bearings were not completely seated when it was installed / tightened. Took it to another shop (since the one that did the initial install was hours away), and they took everything apart, reassembled, and it seemed good to go. Slight whine on coast, but nothing too major.

Fast forward to today, 6 months later. Driving around, there is this cyclic noise coming from the drivetrain at all speeds, but starting / most noticeable above 10mph.

The speed / cycle of the noise is directly related to the speed of the tires themselves. Doesn't matter what the engine speed is, or what gear it's in. (Thank GOD its not the engine.)

I made a chalk mark on the tire and watched it in the mirror to confirm this. If it were the driveshaft, it should be making the noise 4.56 times for every revolution of the tire. It doesnt. 1:1 with the tire. I would suspect the tires themselves except, the noise ONLY happens with a load. Letting up on the gas makes it go away... no noise on coast, even with tow/haul on, really dragging things down.

Any ideas? Ring gear problem maybe? Carrier bearings?

The sound itself is hard to explain. Take the sound of a military helicopter and slow it down to the rotation of a tire. That, or a steam locomotive. Then add in a slight metalic sound to go with it, on each cycle. I swear the metallic sound sounds like the ring gear. The pitch of it, like, if you were to strike it with something. Maybe it's the ring gear bolts letting go in one section, allowing it to rub the pinion gear incorrectly.