Started slipping while in Tow/Haul mode coming out of 1st. Have to get heavy on the throttle and fan it to get it to finically hit second. 2nd to 3rd is a little better and once in 3rd and O/D seems ok and holds.

 

How many miles? When was the last trans service?

 

178,000 miles on truck and transmission was serviced around 120,000 miles. Was told everything looked great then. Could this be a solenoid issue? How would I diagnose to tell if it is the solenoid?

 

Started slipping while in Tow/Haul mode coming out of 1st. Have to get heavy on the throttle and fan it to get it to shift into second. 2nd to 3rd is a little better and once in 3rd and O/D seems ok and holds.

 

While towing? If so, how much weight? The way I understand an automatic transmission, it's supposed to slip until locked up in higher gears than 1st. Mine will lock up if I hold 2nd, 3rd or 4th and it is slipping at least a little until locked. I can make the torque converter slip after its locked if I really get on it, whether towing or not.
On the 04.5 it's OD on /off not tow/haul....semantics.

 

Yes was while towing my 23' jet sled which weighs about 3,000#. I have not yet unhooked it to see if it continues without the boat. Problem is that I am a Professional Fishing Guide and have a boat hooked to the truck just about 24/7. Started off while in tow/haul (OD) off mode and then progressed to doing it with tow/haul (OD) off. I know it says OD, but the readout says tow/haul?