My 1998 lumina hesitates sometimes as it goes up an incline. It almost feels like a miss. The check engine light does not come on. I have replaced plugs, wires, and fuel filter to no avail. The car has a 3.1 engine with 77,000 miles.
What is a TCC solenoid, where is it located, and could this be the problem?

if you shift out of OD, does it still hesitate? if yes, then it's engine related - if no, could be the Torque Converter not releasing correcly - but they tend to shutter.

Have you changed the Ign Module? On my 93 (same engine 3.1) I found it would run really badly when the engine was really working... heat from exh manifold kills these Ign Modules - dumb design in my opinion - they should have mounted it somewhere else, away from heat.

does your tach jump around at all when this problem happens? classic sign of failing ign module... or CPS, but usually, when those fail, they really fail!

just my 2 cents