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4l80e still broke

Wolfrida

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Brand new here hopefully im not in the wrong spot. Hopfully you guys can shed some light on my issues.
Ive got and 06 2500hd with the 4l80e. Started out the tcc was unlocking on the highway as time went on it got more frequent until it just never locked up again? also i notices when in tow mode at higher speeds if i let off the gas the rpms would return to idle?. In addition i noticed when i let my foot off the brake at a light or stop etc, it doesnt move forward as automatics do, when i do accelerate torque gets to the rear wheels but feels as if it lers go a bit, more noticable in reverse? Felt like a bad tranny mount but its solid. Eventually the tranny would go into limp mode, moths later code 1870 trans component slipping started coming up and it started getting hot also i get a random misfire code on the highway if i go over say 60-65 mil flashes. The engine IN NOT missing.

So i pulled the trans brought it to a shop to be gone thru and it still doing every single thing i listed EXCEPT the 1870 code, limp mode and over heating. Oh ya and it whines/whirls in first and second. Took me 6mo to come up w the $$ and the tranny shop has no idea hes telling me try a computer ugh. Frustrated. Day one of my complaints to him about still not locking up he took it for a ride with the scan tool said everything is great! Hes watching it lock etc... day 2 i went down and told him flat out it in not locking up.... then he says ah ya i can comand it on but the computer isnt calling for it well now i just flat out dont believe him. He was hiding the fact it had an issue the first time he drove it so im convinced he knows whats wrong. INSIDE.
During a rebuild do all the electronics get replaced? Because none of the sensors on the outside were replaced. Any direction to the cause or potential issue would be great thank you in advance.
 

WarWagon

Well it hits on 7 of 8...
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i get a random misfire code on the highway if i go over say 60-65 mil flashes.

Day one of my complaints to him about still not locking up he took it for a ride with the scan tool said everything is great! Hes watching it lock etc... day 2 i went down and told him flat out it in not locking up.... then he says ah ya i can comand it on but the computer isnt calling for it well now i just flat out dont believe him.

2+2=4

The engine HAS a problem, period. If there are enough misfires the computer will not lockup or drop out of Torque Converter Clutch lockup. This is to reduce load on the engine and reduce emissions. Less load = less chance of a misfire. Driving it without the TC clutch locked up will heat it up real damn quick and toast the transmission. Park it till it's fixed or buy another replacement for a burnt out transmission.

You should look up MIL light flashing in the owner's manual ... get your foot out of it and if it doesn't stop flashing it's cheaper to tow it than keep pushing it to ruin despite the clear warning to pull over and STOP desperately flashing on the dash!

Your transmission guy isn't an engine mechanic and frankly assumptions that there isn't an engine problem may not be correct. The computer is seeing something wrong, period. Likely it's an engine problem, but, rare to be a computer problem although possible.
 

WarWagon

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when in tow mode at higher speeds if i let off the gas the rpms would return to idle?

FWIW: This is a classic overrun clutch burnt out. Other than a toasted clutch not holding the truck back in 3rd (direct) when engine braking it doesn't prevent the truck from moving forward. I have run a couple 4L80E's this way for over 50K miles. Locking the TCC up when engine braking is a quick way to burn this weak clutch pack up via an override switch or tune. This transmission is HORRIBLE for doing any engine braking: it's cheaper to use the brakes up.
 

dbrannon79

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you need to run a scanner where you can read live data on the sensors, look to see if the ECM is commanding TCC Like @WarWagon says, there are engine issue that will cause it not to allow the TCC to function. simple things like running lean or rich can cause this. look and verify your coolant sensor and others are reading accurately.
 
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