2004 Chevrolet Cavalier Transmission Band Issue

I think you have a different issue going on, but to be safe, have a transmission specialist take the car on a test-drive. The bands keep the rotating gear assemblies in manual low and reverse. They aren't in use in the higher gears. What I suspect you're feeling is the torque converter locking up. It's supposed to do that above around 40 - 45 mph, in the highest one or two gears, when the engine is warmed up. That gives you better fuel mileage. It should unlock at wide-open-throttle to give you more torque, and at released-throttle in preparation for coming to a stop.

The clue is once it's locked up, engine speed can only change when road speed changes, just like with a manual transmission. If engine speed is going up and down while the car is going at a steady speed, the torque converter is unlocking. You can prove this yourself by driving at a steady highway speed, hold the accelerator pedal steady with your right foot, then briefly tap the brake pedal with your left foot. You should see engine speed go up about 200 rpm, then go right back down two or three seconds later.

If that mimics what is happening by itself, you may need a scanner to see why the lockup function is being turned off. There could be a glitch in the throttle position sensor's readings, or more commonly, the brake light switch is misadjusted and one of its multiple sections is activating over bumps in the road.