Ok this might be a little long but trying to understand what I don't understand might be accruing.
Ok the last few times pulling I think I'm feeling what might be tqc slippage I guess? So @ 18-2k rpms in 4th in TH @ 60-62 mph Jr sw1/2 default/default or any other setting, if I give it more throttle to go i'll get quick increase in rpms but no more movement. Like quick rpm jumps about 200ish So I back off. Won't do this in 3rd at all. Well the last 2 pulls I'm now getting a new feel. You know those groove they put on the shoulders of the highways to get your attention if you fall asleep and the feeling and sound you get. Well thats happening in 3rd and 4th gear under load pulling 5th wheel up hills/mountains worse in 4th. It quite erie I must say. I can make it daminish by lightening the throttle.
So is this possible tranny or something else coming apart? I hope not as I really like this truck and it almost paid off too.
Thanks for reading.

 

It sounds like a TC to me. Mine did the same thing when it was going out. Tried to pass on the freeway didn't even kick down but just shook the truck. I ordered a Sun Coast triple disk and a Valve body, big difference now just gotta do all the internals. When I got the truck back the guy told me I need to do a complete rebuild, all my clutches and internals were shot. OH heck whats another $$3700.00 any way, doesn't it grow on tree's???? Any one got a $$$ tree???