Clutch slipping, transmission slipping, or something else

[GShail]

I just pulled off of the highway about fifteen minutes ago from transporting some cars. On the highway the truck flys right along like a mean machine. However when I pulled off the exit and up a steep hill going into town I started getting a herky-jerky motion from the truck, much like you might experience if you were going over a bad washboard road or perhaps had a flat tire. Got out and looked at the truck and crud, no flat tire.

The herky-jerky motion is barely and I mean barely pronounced in first gear, it is quite strong in second, and fairly strong in third. In fourth, fifth, and sixth it seems pretty nonexistent but I kind of think I ran out of hill plus momentum puts a different load on the clutch and trans.

I took a spin around town and went down a hill using my exhaust brake and get the same herky-jerky motion in third and second going down hill.

The trailer has only one heavy car on it, a 61 Deville, and I estimate my load with trailer and car to be about 11,000 to 12,000 lbs.

I got under the truck and don't see any fluid leaks or broken U-joints that I can detect. I have been meticulous about changing fluids in the transmission and the differentials. I am about due for a new clutch.

Please tell me I probably just need a new clutch and that my transmission is likely OK. My transmission has about 90,000 miles on it and the clutch has about 110,000.

Help I need to go to work this week and need to know what you fellas think I am probably up against.

I sure appreciate all the help I have received as a member of this forum.