AW4 1st gear slipping everytime

OK I have a 1990 Jeep Cherokee with an AW4 trans. Its 2wd right now btw. Recently it has been slipping from 1st gear into neutral at stoplights. It wont shift back into 1st gear until I rev up the engine a bit and then 1st gear kicks in (litterally the whole jeep jerks forward). Its only a problem when it is in drive. If I have it in 3rd gear or 1-2gear its fine. Reverse works fine also. I checked the trans fluid and its red and doesnt smell burnt. I also can feel a very bad vibration when decellerating (idk if its relavent). Seems to me like its the rear u-joint but I checked it and it seems fine. Any thoughts?

Sounds like your tranny fluid might be low.

classic faulty throttle position sensor.

The fluid level is good. I checked it when I checked the fluid. I will check the TPS later today when I get home.

EDIT: Im in class right now and cant save links so ima post the link to adusting my TPS here.
http://naxja.org/forum/showthread.php?t=1015963&highlight=TPS+adjustment

Sounds like a TPS issue to me but could also be low fluid, misadjusted TV cable, or bad solenoids/TCU leaving you trying to start moving in OD instead of 1st, in that order.

I just adjusted the TPS. It seemed to be off quite a bit. I drove around a good 5 miles and it totally stopped doing it. Im soo happy now. YAY. Thanks for the reply guys. I wasnt aware the TPS could cause that.