aw4, torque converter / jumping/hard surge. need help troubleshooting!!!

ok guys, im new to this forum thing. havent used it other than to get tech tips for different things, but i am having a problem. my 98'xj,135k. is shifting fine until it goes from 3rd to 4th and only stays in 4th for 2 seconds before the torque converter locks up. that so much does not concern me as much as once it locks in and you gradually get into the gas pedal to accelerate it surges,lunges,jumps kicks,shakes, cant exactly find the right word to descibe it.:rattle: it is like someone it flipping the light switch up and down really fast. locking and unlocking the torque converter or something. it goes away if i tap the brake(thus diengaging the tc) or let off the gas. i have an extra aw4 trans and tc, but not so sure it isnt an electrical or sensor issue. just trying to find some answers or maybe someone who has had the same thing happen and prefereably fixed it lol! thanks guys appreciate any advice
Matt,

Good grief man, what's with the font? That's really hard on the eyes.

My first suspicion would be the Throttle Position Sensor. Second would be the solenoid in the trans which controls the t/c lockup. Here's some info on testing the solenoids with a meter. http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html

Definitely test the TPS.