I have an E4OD with 35 inch tires and a towing package.
The transmission had been rebuilt about 10,000 miles ago.
I have no problems with the transmission until I get on the Interstate for about 30 miles @ about 75 mph in Overdrive then once I get off it starts to upshift extremely hard, especially 1st to 2nd.

What could be the cause of this? Possibly overheating?

After driving around tow for a while the shifts slowly become smoother until there is no harshness.
Also, this problem has been going on since it was rebuilt.

Any suggestions would be appreciated.