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Old 07-13-2021, 02:55 PM   #1
Dmax21
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need some help 4l80e experts

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?
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Old 07-13-2021, 03:48 PM   #2
Ziegelsteinfaust
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Re: need some help 4l80e experts

Have you called tech support for your controller.

They should have a series 9f steps to determine function
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Old 07-13-2021, 03:54 PM   #3
Dmax21
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Re: need some help 4l80e experts

I do not have a transmission controller
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Old 07-13-2021, 04:27 PM   #4
truckin 79
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Re: need some help 4l80e experts

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
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Old 07-13-2021, 05:17 PM   #5
Dmax21
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Re: need some help 4l80e experts

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.
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Old 07-13-2021, 04:48 PM   #6
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Re: need some help 4l80e experts

you saying you dont have a TCM for it?
this would be better moved to engine/trans section...maybe clinebarger will see it
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Old 07-13-2021, 05:03 PM   #7
kwmech
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Re: need some help 4l80e experts

Did the Ls you swapped in have a 4l80e in it originally? Computer come with the engine and harness?
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Old 07-13-2021, 05:19 PM   #8
Dmax21
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Re: need some help 4l80e experts

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Originally Posted by kwmech View Post
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.
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Old 07-15-2021, 03:59 PM   #9
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Re: need some help 4l80e experts

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.
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Old 07-16-2021, 12:29 AM   #10
Dmax21
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Re: need some help 4l80e experts

I'm taking a chance and changing the pressure switch but after I drained the fluid it doesn't look good.
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Old 07-21-2021, 02:08 PM   #11
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Re: need some help 4l80e experts

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.
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Old 07-22-2021, 12:07 PM   #12
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Re: need some help 4l80e experts

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.
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Old 07-27-2021, 03:14 PM   #13
Dmax21
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Re: need some help 4l80e experts

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.
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Old 07-27-2021, 04:13 PM   #14
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Re: need some help 4l80e experts

Quote:
Originally Posted by Dmax21 View Post
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.
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