HELP - 4L80-E won't lockup, then looses 4th gear entirely.
07-24-2009, 05:12 PM
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HELP - 4L80-E won't lockup, then looses 4th gear entirely. Gentlemen,
I did a google search for "automatic transmission forums" and stumbled upon this site. After reading a few threads it seems the members here are pretty authoritative.
I'm complete noob here, but not to forums in general. I tried the search function to find my answer, but came up short.
Also, I'll admit my problem isn't in a car, or with an LS1, it's in a GM truck with a 5.7.
Here's the problem:
It's a 99' GMC K-3500, pushed by a stock 5.7 Vortec, and rarely tows anything at all.
I've run Mobil1 or Amsoil ATF in it since it was new, installed a HUGE B&M cooler, deep aluminum pan, and an external spin-on filter with a Magnafilter on the side. I've also used a Hypertech programmer to firm up the shifting. All this before it had 10,000 miles on it.
Mine just started having hiccups this morning on the way home from work. While driving on the interstate, I totally lost overdrive. When I got home, I noticed the cooling lines were much warmer than normal.
Typically, I can place my bare hand on the cooler lines, and leave them there, when it's at operating temp. Not so today. I assume the higher temp came from not having Torq-Conv lockup.
I allowed it to cool for a few hours, than took it for another spin. It seems the T-Converter never goes to lockup. Then after about 5 miles, I lose overdrive again. Once I lose overdrive, it shifts far firmer than it ever has before, almost barking the tires at times. I understand this may be a "fail safe" mode when things get overheated or otherwise out of whack.
If I stop, kill the ignition, then restart, it goes back to normal shifting. Once I loose 4th, the hard shifting starts.
I've got the OEM service manual set, and it lists one potential cause as "no signal to the solenoid". It says check the VCM/PCM. I have a scan tool and there are no DTC's.
The fluid looks new (was serviced <10,000 miles ago), it's still bright red and doesn't smell burned. The fluid level is normal and there are no signs of a leak, and no odd vibrations. It also shows no signs of lost power. Shifting 1-2-3-4 is fine until I lose 4th altogether.
Any help from the forum members is appreciated.
I did a google search for "automatic transmission forums" and stumbled upon this site. After reading a few threads it seems the members here are pretty authoritative.
I'm complete noob here, but not to forums in general. I tried the search function to find my answer, but came up short.
Also, I'll admit my problem isn't in a car, or with an LS1, it's in a GM truck with a 5.7.
Here's the problem:
It's a 99' GMC K-3500, pushed by a stock 5.7 Vortec, and rarely tows anything at all.
I've run Mobil1 or Amsoil ATF in it since it was new, installed a HUGE B&M cooler, deep aluminum pan, and an external spin-on filter with a Magnafilter on the side. I've also used a Hypertech programmer to firm up the shifting. All this before it had 10,000 miles on it.
Mine just started having hiccups this morning on the way home from work. While driving on the interstate, I totally lost overdrive. When I got home, I noticed the cooling lines were much warmer than normal.
Typically, I can place my bare hand on the cooler lines, and leave them there, when it's at operating temp. Not so today. I assume the higher temp came from not having Torq-Conv lockup.
I allowed it to cool for a few hours, than took it for another spin. It seems the T-Converter never goes to lockup. Then after about 5 miles, I lose overdrive again. Once I lose overdrive, it shifts far firmer than it ever has before, almost barking the tires at times. I understand this may be a "fail safe" mode when things get overheated or otherwise out of whack.
If I stop, kill the ignition, then restart, it goes back to normal shifting. Once I loose 4th, the hard shifting starts.
I've got the OEM service manual set, and it lists one potential cause as "no signal to the solenoid". It says check the VCM/PCM. I have a scan tool and there are no DTC's.
The fluid looks new (was serviced <10,000 miles ago), it's still bright red and doesn't smell burned. The fluid level is normal and there are no signs of a leak, and no odd vibrations. It also shows no signs of lost power. Shifting 1-2-3-4 is fine until I lose 4th altogether.
Any help from the forum members is appreciated.
Last edited by txgp17; 07-24-2009 at 07:24 PM.
07-24-2009, 08:33 PM
#2
If your scan tool can see pending codes, look for a P1870.
Common problem on higher mileage 4L80Es and some years (99-00 IIRC) had a TSB on a cracked converter lockup piston.
Your symptoms are spot on but USUALLY there is a code.
I have seen them without.
The VB will need som new valves installed and sometimes you can get away with just that for a temp repair.
Common problem on higher mileage 4L80Es and some years (99-00 IIRC) had a TSB on a cracked converter lockup piston.
Your symptoms are spot on but USUALLY there is a code.
I have seen them without.
The VB will need som new valves installed and sometimes you can get away with just that for a temp repair.
07-25-2009, 12:30 AM
#4
I have a '92 C3500 with a '98 4L80E.
It was losing lock up, I wasn't looking forward to dropping the pan so I checked the brake pedal switch, thats what it was.
I kicked my foot sideways on the brake pedal a few times and it locked up, I changed the switch, it fixed the problem.
My truck has an OBD1 computer with a chip, I have the equipment to read and burn chips. The trans fault temp varies between the years. It seems the newer the truck the lower the fault temp gets. When it loses lock up the trans gets hot and will either force a lock up or go into limp mode. The chip in my truck is set at 284 degrees, I've seen earlier years like the '91s in the mid 300 range.
It was losing lock up, I wasn't looking forward to dropping the pan so I checked the brake pedal switch, thats what it was.
I kicked my foot sideways on the brake pedal a few times and it locked up, I changed the switch, it fixed the problem.
My truck has an OBD1 computer with a chip, I have the equipment to read and burn chips. The trans fault temp varies between the years. It seems the newer the truck the lower the fault temp gets. When it loses lock up the trans gets hot and will either force a lock up or go into limp mode. The chip in my truck is set at 284 degrees, I've seen earlier years like the '91s in the mid 300 range.
07-28-2009, 06:03 PM
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UPDATE:
I took it to my local GM dealer so he could use a Tech2 device to scan the PCM, which revealed P1870, which translates to "Transmission Component Slipping" in the Service Manual. That was something I already knew, I just didn't know why.
They dropped the pan and valve body and said my Torq-Conv was shot.
I've ordered a replacement from Hughes Performance (part# 25LFuel), and a Premium Overhaul kit (part# HP2589K).
Also, the salesman at Hughes recommended Castrol Type F fluid, rather than Dexron. He also recommended not using any synthetic at all. I'm still on the fence about that one.
I took it to my local GM dealer so he could use a Tech2 device to scan the PCM, which revealed P1870, which translates to "Transmission Component Slipping" in the Service Manual. That was something I already knew, I just didn't know why.
They dropped the pan and valve body and said my Torq-Conv was shot.
I've ordered a replacement from Hughes Performance (part# 25LFuel), and a Premium Overhaul kit (part# HP2589K).
Also, the salesman at Hughes recommended Castrol Type F fluid, rather than Dexron. He also recommended not using any synthetic at all. I'm still on the fence about that one.
07-29-2009, 09:01 AM
#7
type f is not good for a daily driver..it will wear the hard parts eventually. You should use dexron III or dexron VI.
If the converter was working in gears 1-3 then the only thing that could be wrong with your converter is the lockup clutches are toast which would call for a replacement. Unfortunately you were not able to use any of the sponsors here as I feel you may have gotten a better deal and higher quality service for your transmission but a stock rebuild should be fine
If the converter was working in gears 1-3 then the only thing that could be wrong with your converter is the lockup clutches are toast which would call for a replacement. Unfortunately you were not able to use any of the sponsors here as I feel you may have gotten a better deal and higher quality service for your transmission but a stock rebuild should be fine
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07-29-2009, 03:15 PM
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cablebandit,
Thanx again for your input on the fluid. I think you've convinced me to stick with Mobil1.
About using site sponsors.... In hind sight, you're probably right, but where's the best place to look for a full list? I only saw one listed, and they didn't seem to offer anything that appealed to me.
I'm heavily involved in another non-automotive forum and I use site sponsors there almost exclusively.
I've got a 72' TH-350 that will eventually need some freshening up. Maybe I can use them on that one...
Thanx again for your input on the fluid. I think you've convinced me to stick with Mobil1.
About using site sponsors.... In hind sight, you're probably right, but where's the best place to look for a full list? I only saw one listed, and they didn't seem to offer anything that appealed to me.
I'm heavily involved in another non-automotive forum and I use site sponsors there almost exclusively.
I've got a 72' TH-350 that will eventually need some freshening up. Maybe I can use them on that one...
08-25-2009, 10:05 PM
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Gentlemen,
My mechanic has completely rebuilt my 4L80-E, including replacement of all the shift solenoids, the torque converter, the internal wiring harness, the PCM computer, and the brake switch.
The torque converter will still not lockup.
My mechanic removed the tranny, disassembled it to insure he put it together correctly. Reassembled and reinstalled it, and it still does the same thing.
Pretty much every component in the transmission has been replaced or rebuilt.
Does anyone else have a suggestion on what to check?
My mechanic has completely rebuilt my 4L80-E, including replacement of all the shift solenoids, the torque converter, the internal wiring harness, the PCM computer, and the brake switch.
The torque converter will still not lockup.
My mechanic removed the tranny, disassembled it to insure he put it together correctly. Reassembled and reinstalled it, and it still does the same thing.
Pretty much every component in the transmission has been replaced or rebuilt.
Does anyone else have a suggestion on what to check?
08-25-2009, 11:42 PM
#12
Gentlemen,
My mechanic has completely rebuilt my 4L80-E, including replacement of all the shift solenoids, the torque converter, the internal wiring harness, the PCM computer, and the brake switch.
The torque converter will still not lockup.
My mechanic removed the tranny, disassembled it to insure he put it together correctly. Reassembled and reinstalled it, and it still does the same thing.
Pretty much every component in the transmission has been replaced or rebuilt.
Does anyone else have a suggestion on what to check?
My mechanic has completely rebuilt my 4L80-E, including replacement of all the shift solenoids, the torque converter, the internal wiring harness, the PCM computer, and the brake switch.
The torque converter will still not lockup.
My mechanic removed the tranny, disassembled it to insure he put it together correctly. Reassembled and reinstalled it, and it still does the same thing.
Pretty much every component in the transmission has been replaced or rebuilt.
Does anyone else have a suggestion on what to check?
So your mechanic, is a transmission rebuilder or just a general mechanic?
What all did he do to the valve body, specifically the actuator feed limit valve and TCC apply valve?
If he doesn't do transmissions frequently and he didn't take care of the issues with these valve specifically, he could "rebuild" it 50 times and it still not work.
