I drained the differential oil, it was not black, did not smell. There was a small amount of metal dust on the magnet. I drained the oil over a rag, didn't catch any debris. Shined a flashlight in old oil, no shiny particles.

I may have found a shop press out the old bushing and press in the new one (bushing is delivered today). I found a UJ10430 u-joint at Napa. I believe there are 3 u-joints. I will pick up one or more of these. My priority is the rear-most u-joint, as I understand if this one fails it will take out the differential. Next step is to replace bushing and rearmost u-joint.

 

Check the inside faces of brake rotors on your rear wheels. The cause of similar symptoms on my 2004 AWD Sienna evaded me through multiple part replacements and repairs until finally found rust and scale on the inside rotor face of the left rear wheel that was caused realized that sticking caliper slides.

 

Thanks for the idea on rust on the inside of the rear rotors. I will check that.

I got a shop to replace the bushing in "Rear Differential Support No. 1. I needed the bushing to get the van back on the road, but I don't think bushing replacement was a long term fix. The Diff support was pretty beat up, and the shop said that the hole where the bushing mounts was more egg shaped than round. But used car prices are still super high, so some expense and hassle is worthwhile to avoid paying too much for something else.

I removed the driveshaft and checked all the u-joints and center supports. The only issue I found was that the rear most u-joint (connected to the differential) was a little stiff. After much fooling around trying to press old u-joint out, I took the faster, smarter path and cut both the u-joint out. Once the old u-joint was out, I ground out the factory "staking" that secured the old u-joint, and pressed in a new u-joint. The new u-joint has internal c-clips.

I put it all back together, and there is no more popping from the Diff Support... for now. But a new Diff Support is on my list, because the one that is on is pretty beat up. The van goes down the road with much the same noise as before, but without the popping noise from the Diff Support binding up and then thumping the bottom of the van.

One of the rear tires was flat early this week, and when I took it off I noticed a pronounced wear pattern on the inside 2-in of the tread. The wear is an irregular scallop. It may be leading edge wear, or wear from back shocks/struts. Front/rear struts and shocks have been replaced in the last 5000 miles, but the tires have 5 years/25,000 miles. I think the tire wear pattern likely explains the excessive noise. So tires are my next step.

 

Thanks for the idea on rust on the inside of the rear rotors. I will check that. I got a shop to replace the bushing in "Rear Differential Support No. 1. I needed the bushing to get the van back on the road, but I don't think bushing replacement was a long term fix. The Diff support was pretty beat up, and the shop said that the hole where the bushing mounts was more egg shaped than round. But used car prices are still super high, so some expense and hassle is worthwhile to avoid paying too much for something else. I removed the driveshaft and checked all the u-joints and center supports. The only issue I found was that the rear most u-joint (connected to the differential) was a little stiff. After much fooling around trying to press old u-joint out, I took the faster, smarter path and cut both the u-joint out. Once the old u-joint was out, I ground out the factory "staking" that secured the old u-joint, and pressed in a new u-joint. The new u-joint has internal c-clips. I put it all back together, and there is no more popping from the Diff Support... for now. But a new Diff Support is on my list, because the one that is on is pretty beat up. The van goes down the road with much the same noise as before, but without the popping noise from the Diff Support binding up and then thumping the bottom of the van. One of the rear tires was flat early this week, and when I took it off I noticed a pronounced wear pattern on the inside 2-in of the tread. The wear is an irregular scallop. It may be leading edge wear, or wear from back shocks/struts. Front/rear struts and shocks have been replaced in the last 5000 miles, but the tires have 5 years/25,000 miles. I think the tire wear pattern likely explains the excessive noise. So tires are my next step.

I replaced my rear diff support bushing about a year ago. I put the new bushing in the freezer and then tapped the new one with a hammer to get it started into the seat. I remember having a to use a strong oak board and pounding with a 3-pound hammer to finish the job. I do have a very slight play in the rear u-joint on my drive shaft, perhaps about 1/32" at the out circumference. That was not the cause of my wobble problem and I expect the drive shaft to continue for many more thousands of miles before u-joint replacement. My symptoms included what seemed to be lower power on occasion at highway speeds--always when my wife was driving; sometimes a very disconcerting (even a "death") wobble when braking from highway speed while I was driving; and a slower strong wobble at low speeds, say 5-20 mph.

 

The solution was to replace the axle bushings. I believe that the rubber bushings had broken down until road noise was transmitted into the van. The noise, and vibration was very pronounced when riding in the rear seats. With the new bushings installed the van feels very stable and runs down the road quietly.