Transmission Solenoid?

I'm still having shifting problems. My symptoms are as follows:

*vehicle "doesn't know" whether it wants to be in OD or 3rd gear when traveling 45-50mpg. Constant shifting back and forth.

*When coming to a complets stop and then when proceeding to go again the vehicle does not downshift properly, likes to stay in 3rd gear.

*When shifting from neutral to reverse the vehicle does not always go into reverse.

Those are the majority of my symptoms. The vehicle shifts fine when manually shifting and goes into reverse with no hitch when I'm in Low Range. I've checked the MAF sensor and it appears to be functioning just fine. I have a '99 DI with just over 80,000 miles on it.

The tranny has been serviced. That was the first thing I did, althought I did not put in any additive. The MAF was cleaned off and gauged at .08g/sec. When removing the sensor there was a difference in how the truck ran, hence the assumption that it was functioning. I really don't want to have to drop the entire transmission to have it diagnosed.