mrcomps

Yesterday I took the truck out for a long drive. It was fine for about the first 30 km, until I had been doing 90 km/h on the highway for about 20 minutes, I felt this sudden braking force and strong vibration. I let out the clutch and slowed down a bit and it went away. This continued to happen and got increasingly worse - I had to drive at lower and lower speeds to prevent it from happening, and it started happening more often.

The truck has 320,000 km (200,000 miles) and I don't know it's maintenance history, which I suspect is not good. I had just replaced all of the diff, transmission, and transfer fluids before this happening. The oil in both diffs was pretty gross, probably from water, and smelled really bad. The transmission and transfer were both clean but old and foul smelling.

I think that something was overheating, but I'm not sure what. I have a feeling that it was in the rear axle. Is there a way to narrow down what it is, like wheel bearings, carrier bearings, or the pinion bearing?

I ran the truck at 90 km/h with the rear in the air for a while and nothing happened. It might be load dependent, since it went away when I let off the clutch.