Truck has 159k miles
Auto Trans (I believe the 4R44E)

Runs great but 1st gear is a bit rough.

Its reading codes:

P0732 - 'Gear 2 Incorrect Ratio'
P1756 - 'Solenoid B Performance'

Bought the truck about a month ago and have not been driving it much, but sometimes when driving the O/D light will flash on and off.

I have the pan dropped and the trans fluid is very clean.

Based on the research I've done I'm thinking the problem is most likely solenoid b but just wanting to get a 2nd opinion before I change it out.

 

I have a similar experience did you ever figure it out. I put a rebuild trans into the truck worked great for a few months went thru a puddle of water and ever since it loses power, like it doesnt want to go up a hill, the OD light flashes. Put all new sensors on VB all the same codes come back, tried a different VB made things worse, reinstalled the old one and then tried a computer which made it really bad. Before had to drive for about 20 minutes to act up after new computer was installed. So changed everything back to original adjusted the bands a little and thought it was fixed. Went to pass another truck in a hurry and boom issue again, all same codes came back. PLEASE HELP, can anyone help me figure this out.