02 Tranny

[dwelch44805]

I just bought a 2002 3500 4X4 with a Duramax (my wife works at a Ford dealer LOL). It has 185K miles on it but it runs great up to 70 MPH or as long as I stand in it. I drove it home to Ohio from Florida and 17.5 MPG. The problem occurs at a cruising speed. Anything 71 MPH or over and it acts like it is in and out of lock up or overdrive. It seems to be triggered by speed and not RPM. It does not do it in the lower gears at the same RPM. Is it the convertor or possibly a solinoid?
Your comments will be greatly appreciated.

[Kennedy]

How many miles on the fuel filter?

How many miles on the trans fluid and particularly the spin on filter?

Seriously this is the first place to check.