1994 GMC K1500 4x4 Transmission Problems

Be sure that you used the right ATF.For example if F fluid is used in a transmission designed for dextron-type fluid, the shifting will be harcher.

start the engine and allow it to idle for at least one minute. with the parking and service brake applied, move the gear selector momentary to each position ending in park.
recheck the fluid level and add to the level to about 1/8 inch below the add.
# On transmissions with a governor,after starting the engine , move quickly the gear selector to reverse
by quickly placing the transmission in reverse, the chance of dirt entering the governor is greatly decreased
Run the engine until it reachs normal temperature, then recheck it again.

Thanks for the advice. I will try that. I did use dextron-type fluid. I am going to check tomorrow to see if the filter has popped off again.

That an l60E? The filter in those requires a little love tap with your hand to seat in the valve body.The filter shoulkd be parallel to the valve body if its in all the way

I use all the advice above and dropped the pan today. The filter was in place and was parallel. I started the truck and did as instructed by Mathiaso. The automatic trans shifted smooth but after the truck warmed up it wouldn't shift up from 2nd gear. I guess I will need a Trans expert to look at it. I pretty much plan on having to replace the transmission. It has very high mileage. Just can't figure out why it just start doing this after I changed the filter with no pre-existing problems.