Rotational thump while under power

I picked up this 2019 taco In my signature about a month ago. I bought it from the OO with 80k on it. Since I bought it, I’ve changed every fluid, the air filter and the sparkplugs. The two differential fluids were pretty used up. I don’t think they had been changed before. When I go down the highway especially going up a hill. I’m getting a thump thump thump from what appears to be the back of the vehicle. It’s pretty light. I took a visual inspection of everything and didn’t see anything. My rear shaft has no grease fittings. My front shaft has two grease fittings which were dry and I have since greased. All thoughts would be appreciated.

 

Maybe swap the wheels around

 

It seems to be while under power. If I’m coasting it’s not really there? Do you think the tire/wheel could still be the issue?

 

Possibly a bad u-joint. I'd try to wiggle the driveshaft, especially the rear. That sounds like what my 2nd gen sounded like when one of the u-joints took a dump.

 

Get the rear off the ground and try rotating while the truck is in neutral.

 

I moved the driveshaft and ujoint around as best I could while the truck was on the ground. I didn’t notice anything obvious.

 

Good idea. I’ll do that.

 

Has the rear diff oil ever been changed (not like it makes any difference, I guess)

 

Third sentence in OP.

 

My bad.

 

The fluid in both differentials was pretty used up. It was black and gray and not recognizable as the original product. There was a bunch of metal dust/shavings on the magnet, but no pieces of metal.

 

I’d change the center bearing and u joints anyway at that mileage. I’m at 177k and ready to do mine again.

 

I jacked up the rear end and spun everything. I felt the ujoints etc. didn’t really notice anything obvious.

 

Interesting. Did you change all 3 ujoints? Was it a big job? Rockauto des not have the center bearing in stock. Did you put that Ford Blue grease in the spline/yoke?

 

I bought it from the original owner a month ago. . He was a regular 50 year old guy that used it as a car. Trailer hitch was never used. I’m sure he took care of it. He took it to the Toyota dealership for maintenance but just did the bare minimum oil changes, etc., the truck spent some time not too far from the ocean. I’m trying to go through it and clean off any salt etc. that might have accumulated. I’m kind of thinking the salt in the air might’ve been a little tougher on differential fluid and spark plugs, ujoints etc. I’m not sure if that’s true or not or if I’m just making it up

 

Someone else mentioned, move the rear tires to the front, and the fronts to the rear.

Stick to the simple stuff first. What tires, what size and what is tread wear like?

Are the rear brakes sticking? Drive a bunch and brake a bunch downhill. Get them hot, and do the finger check on drums to see how hot they get. Maybe one is seized up?

 

I’ve got a reg cab and yes, I did both ends. I got about 100k out of the oe u joints. Don’t quote me but I think the joints were moog 280 (for mine, anyway)