Help! Transmission (4L60E) intermittently does not work

[Isaac Riffel]

So I have this 2000 Silverado with a 4L60E auto transmission. It’s got over 200k miles. The 4.3 v6 engine runs great, but half of the time the transmission will barely move the truck. (This is a standard cab 2wd version.) if I’m stopped and I put it in reverse I have to give it a really heavy push on the gas to get it to move.. but on the other side of the coin it will work fine sometimes. The transmission will search aimlessly for a gear but works fine once it finds one. Some days it won’t go over 30mph and other days it works just fine. Could I just have a bad filter or something or do I need a new transmission? Thanks!

[Mike GMC]

What does the fluid look like, and is it full?

[sefiroxx]

And drop the pan to see if anything is in it. If clean fluid and clean pan, then valve, colonic or wiring work.