rear diff. rumble - help sought

Hi,
My new (to me) '99 ext cab 4 cyl 5 sp truck with locking rear diff. has a rumble in the rear. It was evident on straight road, acceleration and deceleration, especially up to about 40 mph, then it becomes less evident. I lifted it up and ran it to listen to the rear end. The wheel bearings sounded silent. The noise came from the diff. The drivers side axle has a sort of catch as it gets rotated.

We removed the 3rd member and put it in a vise. There was a small metal "thing" stuck to the magnetic plug. It looks like a piece of metal from the bottom of a drilled hole - sort of like an egg shell, about 5/16" diameter, and NOT all chewed up. The drivers side output (where the axle engages with the diff) has the "bump" or whatever, evident by putting your fingers in where the axle fits, and rotating the spider gear assy. The "bump" is more noticeable if you also push the spider gear assy in from the passenger side, while rotating the driver side.

The ring and pinion gear look and feel great.

My buddies and I are hesitant to tear down the diff. as we don't have some of the tools called for, and have never done one before. We're trying to decide if I would be better off taking the 3rd member to the local Toyota shop or just buy a new/rebuilt/used 3rd member and be done with things.

I've searched this forum, but haven't come across this particular complaint. Any ideas or suggestions?

Thanks very much. Paul Underwood

 

Hey Paul, sounds like the course of action you took was good, being a locker rear end it's best to make sure it's operating correctly, what ever was making the noise or vibration certainly wasn't going away, I wonder how much slop it would take to do this ? I bet they find a piece thats broken off inside, and doesn't start trouble until the speed builds up. Good luck

 

Thanks Jedi for the reply. An update: We've found one tooth on a spider pinion gear (Not the ring/pinion) with a small chip on one corner, but it does not appear to be a mating surface. The drag is noticeable when pushing in on both side gears and turning the spider assy. We've checked tolerances in the spider and they seemed within specs.

I plan to reinstall the 3rd member and axles as before and retest things, paying special attention to any other noises (tranny, xfer case, etc.). If the problem is still on the drivers side axle, I plan to switch axles side to side. If the problem is still drivers side, the axles should both be ok. Assuming they are ok, I'll pull both axles and try to get the rumble. If it isn't there at all, I have to assume it is in the spider assy, which shouldn't be moving at that point (if I'm not mistaken).

Paul