I just had my trans rebuilt at 49K, the dealer rebuilt the torque converter, and a bunch of stuff in the trans. I now have 51K and I was towing my fifth wheel in tow/haul mode and at 30 mph the tran rapidly shift all the way to top gear. When I pressed on the pedal to the floor it stayed in top gear...it did this 3-4 times between 30-40mph starting from a take off. I had to manually down shift. Twice the truck would not shift down into 1st gear from a dead stop. After towing driving home for about 50 miles in reg trans mode, no issues except it is having trouble finding 2 gear.
I have a 4 speed, not sure of the model. I would like some tech advance to give to the mech, as it took may dealer/mech 20K miles and a couple of personal rides to get them to repair the tranny once already. They had to drop the pan to find parts before they rebuilt the tranny. Any advice on what this could be, I woud appreciate it...yes I have to go to the same dealer because they fixed it under waranty and now it is out of waranty and they said they would fix it again.

 

well can say the dealer themselves did not rebuild the converter they probably stuck either a new or reman in it. as for the shift concerns it sounds like you have a concern in the valve body ! did they replace or clean that? it could be the pressure sensor or transducer not giving and accurate line pressure reading, but then it usually starts in second gear, sounds like they need to drop it out and look at it again. did they drop the pan yet ? find anything again otherwise if clean would suggest valve body more than likely a 47re or a 48 re in the pickup for a trans keep us informed