need some help 4l80e experts

[Dmax21]

just did a ls swap on 84 and bought a 4l80e from the junkyard with unkown of the condition but the fluid looked good, now that i have it installed you can feel it go into reverse but will not move and it will go into D and not move but i can put it into 123 and it will pull fine, has anyone had a problem like this? it did have p1810 code which is the manifold pressure switch and i am replacing that but i'm positive that will not fix it. Do any of you guys have any suggestions?

[Ziegelsteinfaust]

Have you called tech support for your controller.

They should have a series 9f steps to determine function

[Dmax21]

I do not have a transmission controller

[truckin 79]

I am no expert but sounds like what my Avalanche was doing when transmission went out. I was driving one day and came to a stop, I then went to accelerate and engine revved up but vehicle went nowhere. I figured out I could manually shift Avy to get it home. The dealership did not ever tell me what was the problem just said bad tans and swapped it out. Did you make sure fluid level is correct?
Good luck

[mongocanfly]

you saying you dont have a TCM for it?
this would be better moved to engine/trans section...maybe clinebarger will see it

[kwmech]

Did the Ls you swapped in have a 4l80e in it originally? Computer come with the engine and harness?

[Dmax21]

yes the fluid level is good, i was figuring it would be bad but was also hoping that maybe it could be something simple since i know very little about automatic transmissions.

[Dmax21]

Originally Posted by kwmech

Did the Ls you swapped in have a 4l80e in it originally? Computer come with the engine and harness?

no it had a 4l60 but i had a harness built for the 5.3 and 4l80 trans and a local guy tune the computer for the 4l80.

[Nick_R_23]

It sounds like you either have a bad pressure switch manifold or incorrect wiring (or possibly tune) for the transmission, as when you are engaging Reverse and Drive, you are likely engaging more than one gear, which is why the transmission feels like it’s binding or won’t move.

[Dmax21]

I'm taking a chance and changing the pressure switch but after I drained the fluid it doesn't look good.

[Honest Bob]

You need to check that the dipstick is actually reading correctly. You may be low on fluid and not even know it.

This video steps you through the process of calibrating your dipstick.
https://www.youtube.com/watch?v=DBULieFxGsk

What ecu are you using? If the ecu originally controlled a 4l60e its not going to work right on a 4l80e. Its also possible if you sent it out to have the ecu tuned that it might not be tuned correctly.

The trans connector can sometimes be positioned upside down. Try unplugging rotating and reinstalling it.

Jack up the truck put it in neutral and see if the wheels can spin freely. Maybe something is locked up causing the truck not to move.

[GRADYS Performance]

If it moves in 1,2 and 3 the trans is probably ok. It would seem that the problem you have is in your computer system not being compatible with the 4l80E.

[Dmax21]

the computer was for the 5.3 dbc and it did originally have a 4l60 but was no good so i swapped it too a 4l80e, I had a stand alone harness built for the engine with the 4l80 transmission as far as tuning goes it was done by a local guy that did a base tune and he said he set it up for the 4l80, i know nothing about tuning so i'm just going by what he said.

[GRADYS Performance]

Originally Posted by Dmax21

I'm taking a chance and changing the pressure switch but after I drained the fluid it doesn't look good.

What did the fluid look like? Bottom of the Pan, Sediment, Clutch and band material, Bass shavings, Steel shavings, and or pieces of anything? That will give you a good idea of the condition of the mechanical parts of the transmission. You can also take a pressure reading to see what the hydraulic condition of the transmission is. You can get pressure readings both low and hi at the TCIATUO.com website under the technical resources.

[Honest Bob]

Originally Posted by Dmax21

the computer was for the 5.3 dbc and it did originally have a 4l60 but was no good so i swapped it too a 4l80e, I had a stand alone harness built for the engine with the 4l80 transmission as far as tuning goes it was done by a local guy that did a base tune and he said he set it up for the 4l80, i know nothing about tuning so i'm just going by what he said.

If you've tried flipping the round trans connector 180 degrees and its still not working right the wiring and tune need to be checked out. The 4l80e defaults to 2nd gear in limp mode.

[Dmax21]

Fluid is new with only about 10 min run time and just putting it in gear to see if it would move and it looked awful, I'm pulling it and taking it to a shop.

[GRADYS Performance]

Did you have the pan off and clean it when you put the fluid in before this drain? If so what did the fluid and pan look like then?

[Dmax21]

Originally Posted by GRADYS Performance

Did you have the pan off and clean it when you put the fluid in before this drain? If so what did the fluid and pan look like then?

yes i bought it from a pull a part and when i got it home i drained what fluid it had left in it and it was really dark but i dont know anything about this trans like how many miles or service history but i do know the pan had been off before and the drain plug was pretty much stripped. so i took the pan off and cleaned it really good and put a new gasket on and put new fluid in it and that is what it looked like after only putting into drive and reverse a few times but low gears 123 it would pull but when you put it into D nothing and R nothing, you could feel it try too engage and would act like it wanted to pull while idling but soon as you press the gas it would do nothing.

[GRADYS Performance]

That much sediment from a few minutes running means the transmission most likely has internal issues that would require a rebuild.