4L80E transmission problem

my 2003 2500hd has the 4l80e.

I can tell you the Torque Converter (TC) unlocks in 3td and it creates a lot of heat - so much that I try not to tow in it. I have a 16 pass stacked plate trans cooler (downstream from the radiator cooler) and on flat level ground I run at 165 - 175 consistently (when it's about 90+ degrees outside).

When I pull in 3td gear, that temperature rises up to between 195 - 200 degrees.

Climbing hills it's similar in temperature (sometimes up to 210-220) but it's on a 14mile hill climb, in 2nd gear, wide open throttle). As soon as I crest, the temp drops back down (depending on the gear of course).

I have often lamented about my 4l80e and how it shifts and it's random shift points (both in and out of haul mode). The longevity of the transmission, towing though is a sign that the engineers know what they were doing with this transmission. I've got over 152,000 miles on it, pulling my 5er and daily city driving. I do have the pan dropped, and the filter changed annually and had the fluid flushed. That allows me to have the particulate matter inspected and thus far, nothing has been burned.

I wish I could control the shift points as well as the TC though!

Will try and get to that first of the week, Thanks.

Here is one link from a bing search for cable. Cable adjustment

Here is one in question shift down. Shift down

Can you tell me how to know its proper position?

Throttle position sensor is on the right side near the manifold.
Check to see if shift cable is adjusted correctly.

When I am going up hill it will drop out and if I let off on the gas it will hold but I am slowing down and if I give it any gas it will start to slip, I even would try and feather the gas but I am still slowing down and if I give it more just races (slips more)so I back down and try and feather the gas to make it up the hills, now these are not real steep hills, think my problem is in the sensors. I am not sure just where they are but it was mentioned at the throttle body, I have no idea where that one is.

The slipping you are feeling could just be the torque converter unlocking.
The t/c will lock in 3rd or 4th gear. When you downshift from 4th to 3rd the t/c will unlock then if load and speed conditions are right it will lock back up.
If loads are high (throttle further open) it will stay unlocked to let the rpm's wind up to help acceleration.

how does it behave if you just leave it in overdrive?

Does it downshift from 4th to 3rd on its own on hills and does it still give you the same slip feeling?

The 4L80 is a relatively tough transmission, with a proper size fluid cooler and routine fluid changes it should last a long time.

Just had it fully rebuilt was what I was told, supposed to be a good shop around here, I think I have the transgo kit around here somewhere but could not find a shop that wanted to install it. this was the first trip on the rebuild about 1,000 miles, I am not sure about the sensors being changed, do you know just what controls the shifting? is it separate from the transmission? I pulled this transmission out myself and took it to the rebuilder then reinstalled it, only a one year or 12,000 mile warranty, I am past that.

I have that same year trans and chassis. It will slip as you describe in 4th gear as the torque converter will unlock, if you let your foot off the gas the slipping will stop. There is no slipping in 3rd gear. Do you know what the rebuilder actually rebuilt the second time around? It may be a reoccurring failure in one of the sensors. Has the fluid ever been changed?

Did you replace the torque converter?