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4L80E Questions

B

BronKitis

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I have a 1992 K2500 W/6.5 TD. For a while now, at freeway speeds she would shift in and out of OD very quickly and sometimes take about 3-4 min to shift back into OD. It has recently gotten worse. Also, at a stop, I would get the check engine light. When I would go to accelerate I noticed it took about one second for the torque converter to engage and actually move forward. Last Friday I was on my way to work and all the sudden she went in to limp mode. I drove it to my local tranny shop in hopes they would fix it.

They told me that shift solenoid A and B were bad and that my ECM needed replacement. It only threw two codes total and for the life of me they would not tell me exactly which codes were thrown. I am presenting all the info I have to the fine member of this forum in hopes that I can really dig into whats going one with my poor old girl.

They wanted to charge me over 400 dollars to replace the ECM alone, so I told them no and that I would take care of the issue. I found a 4L80E from a buddy with 50K on it with t-case for 600 bucks including wiring harness. I plan on just swapping this setup into my truck to see if this fixes the problem. Can anyone think of anything else I should check before or after doing the swap? I really need my truck back and have no experience with this type of transmission at all. Thanks in advance!

AJ
 
check ALL your gounds they reak havok on the trans, also on my 95 i thought i needed a trans it was doing similar things and i found a bad CTS i changed it and the problems went away.

recently i had a 2-3 shift problem for a day and it went away on its own but then to day i got in it and it would not shift out of 1st. , no codes. I have plans to pull the pan pop out the shift sol. and clean them along with the presser manifold. I have had good luck with this in the past.

also try unpluging the speed sensor on the tail shaft and drive it. you will not have a speedo but it will make the trans shift at its defaults.
 
Ok. Grounds... Just love grounds! lol. What is a cts? I don't know if I should replace the ecm first or go for the gust with the tranny... Suggestions?
 
So I didn't get the code numbers but I did find out the 2nd code thrown was "quad drivers module" which is in the ecm. I have no idea what that means...
 
check the harness at the transmission end. If you've got the old style(91-92) with the bolt in the middle they have a bad issues with leaking. wiring + tranny fluid makes funny things happen.
 
i would check the wiring and pass trough harnass connector for corrosion and the ground on the pass side rear of head.
you can ohm test the solenoids at the connector,I think 20 OHM min.

Or you can drop the pan and replace the solenoid,good idea anyway,they're cheap.TCM would be your last resort,only 150 buck or so.
If you delete the codes, they will reset after the problem re occurs
 
the mess of the ground hookup is just horrible. on mine they was 4 different ground going to the computer. add that to the TPS, fuel heater and something else(can't remember) you can figure out what the wiring looks like.
 
They told me that shift solenoid A and B were bad and that my ECM needed replacement. It only threw two codes total and for the life of me they would not tell me exactly which codes were thrown. I am presenting all the info I have to the fine member of this forum in hopes that I can really dig into whats going one with my poor old girl.Thanks in advance!
Click to expand...

If your PCM didn't throw a code for bad solenoids then the circuits are good to those solenoids.
However the pressure testing could have verified the shifting solenoids. I doubt the shop pulled the 1-2 and the 2-3 and pressure tested the solenoids.
I doubt it if they checked for shift times either.

They told me that shift solenoid A and B were bad
Click to expand...
Kind of a coincidence that both would go bad.


ECM needed replacement. It only threw two codes total and for the life of me they would not tell me exactly which codes were thrown.
Click to expand...
For the life of you they want your paycheck.

I really hate people like this. They piss me off like no other. Either the PCM is bad and will not command shifting solenoids or a solenoid goes bad. Rarely do both go bad.
Sounds like a fear to fix. I lay on the fear to you to fix.

Chances are these people would have replace the pcm/ecm, solenoids and not fixed the problem. You would have then been stuck with the bill.
Verify voltage from Pin E at the passthrough connector at the transmission. Ignition on, Pin E is the only one in the middle.
12 volts dc. Pin E and A for the 1-2 transmission end. Ohms @20 or so. E to B for the 2-3. Same ohms.

Computer controls through grounding. 1-2 through pin A. 2-3 through pin B.
It is as simple as that.
If you are shifting from 1st to second to third these people are blowing smoke.
 
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