Here's the story. 2003 5.9l auto 4x4. Everthing seemed fine until today when driving to work it seemed like it switched outa gear. Pressing the gas just reved as if it were in neutral. I tried shifting it into reverse, first, second, and nothing in any gear. I shut the truck off and started it up again and it began working again. On my lunch I went back out and again it wouldn't go into any gear just kept reving. Again I shut it off and retarted and after 3-4 times doing this it finaly started working but after driving for 2-3 min it just went back to reving. I had a engine code before of P0740(i think, it was something with the torque converter) but i cleared it and it hasn't come back. I'm thinking it has to be something electrical like a sensor or something but not sure. Any ideas? Need any other info?

 

You could start with changing the fluid and the filter, a clogged dirty filter could cause this. Be worth a try, anyway. Doubt very highly it's just a sensor, because that would usually generate a CEL, but the tranny should perform as normal.
Most likely you are looking at a rebuild...

 

I did have a code of p0740 or p0720. Would either of these codes have anything to do with my problem?

 

yeah, could be the start of your issues. The output speed sensor and the torque converter out of spec. Again, these are not "major malfunction" codes. If it were just the sensors failing, your tranny would perform normally. The fact you have shifting problems and a torque converter that is not "grabbing" properly is indicative of a problem inside the transmission.
If you want to try the only possible easy fix, then change the fluid with fresh, change the filters and hope for the best. I think it's gonna need a rebuild, but I've also seen a clogged filter throw codes and make the tranny not shift...

 

Couldn't hurt to tighten the bands, since you're in there anyway. Will require an in/lbs torque wrench. Could just be low fluid, but certainly worth changing fluid and filter(s).

 

I would take it to a reputable Transmission shop (ask your local car parts store's they usually will know who is good) have the shop look at it. I lost Reverse on my truck but every other gear worked perfect. I dragged my feet and tried the whole change fluid, filter deal to no prevail. Once I had the tranny pulled for rebuild they showed me the inside. I really beat up the case and did a lot of additional damage because I dragged my feet. I would get it looked at by a professional immediatley. Good luck

 

Couldn' hoit. The diagnostic fee can be applied to the repair. Nationwide seems reputable. NOT Cottman or Aamco, though.

 

Well got it towed to a tranny shop today. He called and said that the filter was clogged and also that the torque converter is "loading up" or something like that. He's going to drop the pan tommorow or monday to see if there's any particles floating around. Hopefully nothing in the tranny is messed up.