Jrgunn5150
Enjoying tomorrow's success today
Funny, because I've probably built a dozen of these, but never owned a truck with one.
Pigpen has a host of transmission problems, so I'll run through them and how I fixed them, since we don't seem to have much 4L80E info here.
When I bought it, it was shifting harshly. And not, nice shift kit firm, but, going to break something real soon hard.
There is a connector on the side of the transmission, that sometimes leaks internally, and causes all manner of havoc internally. If you pull your's off from the outside, and see ANY fluid in it at all, any, one drop. Replace it. Here's an example.
https://www.amazon.com/4L80E-Internal-Wire-Harness-1994-2003/dp/B009GNB05Q
Now, since I had to replace the harness anyway, I simply bought a kit that included both shift solenoids, a new pressure manifold, EPC or force motor, and a TCC Solenoid.
Usually shift solenoids will exhibit flaky shifting (go figure right?), or a flat out failure to shift. The force motor, or EPC, is what controls the pressure throughout the trans, it's likely what Pigpens problem was to begin with.
My current problem, is that four or five miles of driving in, Pigpen abruptly shifts out of OD, into D. After that, no amount of acceleration, monkeying with the shift lever, engine restarts, or anything else will get it back into OD. Until it's cold again. Leave it sit overnight, come out, it's good to go another 6-7 miles.
My research has taught me, that if the PCM doesn't see converter lockup once the trans reaches operating temp, it will command a shift into third.
The reasons why are complicated. Could be a bad TCC Solenoid. I just changed it, maybe I got it int here wrong, maybe it was bad out of the box. Could be the TCC Valve behind it, Sonnax has an upgrade for it, here, Sonnax 34994-01K. It's 30 bucks, and worth a shot.
Why does the TCC valve go bad? PWM. GM, in designing the trucks for comfort, decided the converter lockup should be gentle and modulated, so they stroke that valve a billion times a second to slowly apply the TCC so the MILF in the Suburban doesn't get a firm converter apply. But it's a hard anodized valve in a virgin alloy bore, so, it wear's that bore out over the course of 200,000 miles, until so much fluid leaks past it, the TCC Solenoid doesn't get enough pressure to tell it to apply the converter clutch.
The next possible cause, is a bad AFL valve. This is a actuator feed limit valve, to be technical. This experiences similar bore wear to the TCC valve. After 200,000 miles of wiggling around in there, it wears the bore. This can be fixed on of two way's, that both suck honestly. Transgo 48-ACT-TL includes a reamer tool, and an oversized bore. The fix is good for at least 100,000 miles, but who knows? It's still a steel valve in a aluminum bore, so it will wear. Also, it's 100 bucks, and comes with 6 valves. Only have one truck like me? They don't care, it comes with 6. Go be a 4L80E vigilante and repair other peoples trucks by dark of night, or whatever, because you cannot buy a single one. Option 2, is Sonnax 34200-16K. It's 40 bucks, comes with a steel liner to go in the bore that will never wear, and requires a 350 dollar reamer to install. Bummer. I chose to find a shop local to me that is aware of the problem and has the Sonnax reamer install mine for me.
Another cause can be a flaky brake switch, they go bad, but your brake lights still work properly. If the PCM think's the brakes have been applied, it will unlock the converter. Thus, you never get lockup, and downshift to third.
Finally, the cause no one wants to hear, it could just have a bad converter. It happens, especially when other issues are let go too long. Replace it and be happy, if you can, get a tune that disables the PWM function, and you'll probably never have another problem with it again.
Pigpen has a host of transmission problems, so I'll run through them and how I fixed them, since we don't seem to have much 4L80E info here.
When I bought it, it was shifting harshly. And not, nice shift kit firm, but, going to break something real soon hard.
There is a connector on the side of the transmission, that sometimes leaks internally, and causes all manner of havoc internally. If you pull your's off from the outside, and see ANY fluid in it at all, any, one drop. Replace it. Here's an example.
https://www.amazon.com/4L80E-Internal-Wire-Harness-1994-2003/dp/B009GNB05Q
Now, since I had to replace the harness anyway, I simply bought a kit that included both shift solenoids, a new pressure manifold, EPC or force motor, and a TCC Solenoid.
Usually shift solenoids will exhibit flaky shifting (go figure right?), or a flat out failure to shift. The force motor, or EPC, is what controls the pressure throughout the trans, it's likely what Pigpens problem was to begin with.
My current problem, is that four or five miles of driving in, Pigpen abruptly shifts out of OD, into D. After that, no amount of acceleration, monkeying with the shift lever, engine restarts, or anything else will get it back into OD. Until it's cold again. Leave it sit overnight, come out, it's good to go another 6-7 miles.
My research has taught me, that if the PCM doesn't see converter lockup once the trans reaches operating temp, it will command a shift into third.
The reasons why are complicated. Could be a bad TCC Solenoid. I just changed it, maybe I got it int here wrong, maybe it was bad out of the box. Could be the TCC Valve behind it, Sonnax has an upgrade for it, here, Sonnax 34994-01K. It's 30 bucks, and worth a shot.
Why does the TCC valve go bad? PWM. GM, in designing the trucks for comfort, decided the converter lockup should be gentle and modulated, so they stroke that valve a billion times a second to slowly apply the TCC so the MILF in the Suburban doesn't get a firm converter apply. But it's a hard anodized valve in a virgin alloy bore, so, it wear's that bore out over the course of 200,000 miles, until so much fluid leaks past it, the TCC Solenoid doesn't get enough pressure to tell it to apply the converter clutch.
The next possible cause, is a bad AFL valve. This is a actuator feed limit valve, to be technical. This experiences similar bore wear to the TCC valve. After 200,000 miles of wiggling around in there, it wears the bore. This can be fixed on of two way's, that both suck honestly. Transgo 48-ACT-TL includes a reamer tool, and an oversized bore. The fix is good for at least 100,000 miles, but who knows? It's still a steel valve in a aluminum bore, so it will wear. Also, it's 100 bucks, and comes with 6 valves. Only have one truck like me? They don't care, it comes with 6. Go be a 4L80E vigilante and repair other peoples trucks by dark of night, or whatever, because you cannot buy a single one. Option 2, is Sonnax 34200-16K. It's 40 bucks, comes with a steel liner to go in the bore that will never wear, and requires a 350 dollar reamer to install. Bummer. I chose to find a shop local to me that is aware of the problem and has the Sonnax reamer install mine for me.
Another cause can be a flaky brake switch, they go bad, but your brake lights still work properly. If the PCM think's the brakes have been applied, it will unlock the converter. Thus, you never get lockup, and downshift to third.
Finally, the cause no one wants to hear, it could just have a bad converter. It happens, especially when other issues are let go too long. Replace it and be happy, if you can, get a tune that disables the PWM function, and you'll probably never have another problem with it again.
