1997 Pathfinder torque converter locking and unlocking

[AlwaysWrenching]

During normal short drives the transmission works fine. However on long drives the torque converter starts locking and unlocking at around 60-70 mph. Over 80 mph it's fine. I'm thinking it the torque converter control solenoid. Is there any test for it or just replace it and see? 

[XPLORx4]

Does this happen on all long drives at between 60-70mph, or only on certain sections of the road? It is possible that the road grade is just barely steep enough to cause the TC to unlock and lock. Do you have oversized tires? Does it also happen when you lighten up on the accelerator or only when under low load?

[AlwaysWrenching]

Totally stock tires. New transmission filter and fluid. The torque converter locks and unlocks so much it's annoying while driving. Usually a bit of hard acceleration and it stops for a while. It did get better after changing the transmission fluid and filter, but then after about 1700 miles started acting up again. There was a lot of sludge in the transmission. 227000 miles. 

[Slartibartfast]

If you've got a code scanner that'll do live data, plug it in and check the throttle position sensor. Press the gas pedal slowly, see if the percentage changes in proportion to where the pedal is or if it jumps all over the place. If you've got a dead spot where the reading jumps around, that could be why the computer is reacting to inputs you're not giving it.

 

IIRC the R50 has the same blinky-lights trans diagnostic system as the WD21, should be spelled out in the AT section of the service manual. Worth running those codes too on the off chance the computer has any idea what's wrong.