transmission question

I just got a 96 explorer for next to no $. Even if I have to replace the tranny, it's a good deal. There again, don't want to if I don't need to. The problem is when I'm doing 70 and apply gas, the RPM's increase, then begin to decrease again, without my letting off of the gas.

I have no basis of comparison for this car, as every car I've owned has been pre 1957, or a standard shift.

There are no other malfunctions, no lights, nothing.

Any thoughts?

Could be a few things, fuel filter, pressure regulator, maybe even MAF, does it do it any other time at other speeds?

If the change is about 300 rpm it is probably the torque converter clutch locking and unlocking. I would check the throttle position sensor. These get intermitant in the range they are usually at. Trans could be thinking you are trying to accelerate.

Where is a throttle position sensor, and how is it checked? Thanks!

The TPS is located on the engine under the throttle body cover. A black device with three wires. A voltmeter is connecte to the center wire and one of the others. The throttle is then moved and you look for a smooth change in voltage.