Driving on the highway, the engine rpm started fluctuating between 1900 and 2400. Seems pretty random but, more noticeable when it is hot. Not so noticeable when started cold it takes about 30 minutes for it to start happening.
Was 400 miles from home when it started. Took it to shop and had it scanned on a Snap=on scanner. Came up as trans solenoid. mechanic thought it was TCC but not sure. Suggested I should be able to get home without using overdrive.
Drove the 400 miles home, had to stop and let it cool down several times,
It would act up even in drive after an hour or two. Seems to drive fine in first and second. Whats my next move?

Get the exact code and check the condition/level of the transmission fluid....

the exact code was p1671 ml solenoid.
Just had the trans out about 10 months ago to replace the rear main seal. Changed the fluid and filter at that time. First thing i did when it started acting up was check the fluid level. It was just a shade above the full line so I bought a little suction pump at the truck stop and syphened a pint out of it. It did not seem to have any impact on the symptoms.

Not sure what P1671 is, but it is not a transmission solenoid issue......Transmission codes are P07XX or P17XX.....

I must have wrote it down wrong. He had a Snap on scanner and it said ML solenoid. It did not say TCC solenoid specifically. He thought it meant TCC solenoid was not not sure. He had just purcchased the scanner a few weeks before. I have been wanting to buy a scanner, I guess now is the time. Do you have any suggestions?

Update. Let the car sit until November then started driving it again. Have not driven it more than an hour yet but, it shifts fine and have not had any problems.
I plan to continue driving it until it acts up again. I think it is going to be fine until it gets hot next summer.

I have been driving it daily ever since my last post. Probably put 25.000 miles on it.. Has not missed a beat. The wonders never cease.