4L80E Transmission Problem

fbhart@wk.net · 03-06-2008, 08:04 PM

I have a 2000 Chevy 3/4 ton, 350 engine (255 hp, 330 # torque) with a 4L80E transmission. Transmission serviced at 60K. Spec said it would tow 7100#, but believe me it cannot even tow 6000# without breaking down.

The piston cracked in the torque converter at 78K miles. This truck has never pulled over 6000# and that was few times, even then it was always pulled in thrid gear, never in OD.

The truck is down getting a new troque converter installed and general transmission review.

This transmission must be weak, I cannot believe GM would place this transmission behind a diesel engine truck.

Just venting,
I thought I had bought enough truck to do the job. Guess I should have gotten a Dodge diesel with manual transmission.
Should have figured it out, cars have automatics and trucks have manuals.

75K30 · 03-07-2008, 01:40 AM

Too bad about your mis-fortune with regards to your trans.
However I have to completely disagree with,,,,well, about everything you have stated about the 4L80E. This is a great transmission, and is extremely reliable, and plenty capable of surviving small loads like 6,000 Lbs.
I am a little fuzzy on this piston that failed in the converter. I can only assume that the converter piston responsible for the lock-up of the converter itself. This can fail for many reasons, and proably not a result of towing. As a matter of fact, towing in OD for newer transmissions is not only a decent idea, but often recommended to keep the transmission cool. You could have overheated the transmission and created a problem with the lock-up clutch itself, or even made the dampening spring fail. If this fails, the torsional force applied upon clutch engagement will promote shock transfer, and failure will result. This will occur whether or not you have a trailer, and rear axle gear selection is really very critical here.
Have you changed the rear axle ratio by any chance? Lower ratios are far superior for transmission life than a highway gear, especially when small engines and trailers are thrown into the equation.
I hate to hear of any unfortunate failures, and in this case it sounds rather unfortunate, but I believe you have been dealing with a damaged trans for a little while, and this is probably due to a variety of factors, and not directly related to the design of the 4L80E.
FWIW, I have pulled (on several occasions) a 3 axle, 36 foot toy hauler (over 10K lbs) with a Big block, and a 4L65E. (no correction needed, it is a 65, not a 60, although they are almost identical, and still much smaller than a 4L80E.)
Have pulled this trailer on many trips loaded to the gills, with not a single transmission related issue.. I would not hesitate to do this with a 4L80E any time. Key to success is to keep it cool, and auxillary coolers are a must, but just as important, the ability to lock-up the converter while towing. I see temps vary over 50 deg while towing out of OD, and no lock-up.
MAybe try a gauge on the trans, and you will see what I mean. If you have been towing 6K lbs on a stock cooler, and running without lock-up, I believe you will experience this problem again unless it is addressed.
Just a thought.

fbhart@wk.net · 03-08-2008, 03:26 PM

Quote:

Originally Posted by 75K30

Too bad about your mis-fortune with regards to your trans.
However I have to completely disagree with,,,,well, about everything you have stated about the 4L80E. This is a great transmission, and is extremely reliable, and plenty capable of surviving small loads like 6,000 Lbs.
I am a little fuzzy on this piston that failed in the converter. I can only assume that the converter piston responsible for the lock-up of the converter itself. This can fail for many reasons, and proably not a result of towing. As a matter of fact, towing in OD for newer transmissions is not only a decent idea, but often recommended to keep the transmission cool. You could have overheated the transmission and created a problem with the lock-up clutch itself, or even made the dampening spring fail. If this fails, the torsional force applied upon clutch engagement will promote shock transfer, and failure will result. This will occur whether or not you have a trailer, and rear axle gear selection is really very critical here.
Have you changed the rear axle ratio by any chance? Lower ratios are far superior for transmission life than a highway gear, especially when small engines and trailers are thrown into the equation.
I hate to hear of any unfortunate failures, and in this case it sounds rather unfortunate, but I believe you have been dealing with a damaged trans for a little while, and this is probably due to a variety of factors, and not directly related to the design of the 4L80E.
FWIW, I have pulled (on several occasions) a 3 axle, 36 foot toy hauler (over 10K lbs) with a Big block, and a 4L65E. (no correction needed, it is a 65, not a 60, although they are almost identical, and still much smaller than a 4L80E.)
Have pulled this trailer on many trips loaded to the gills, with not a single transmission related issue.. I would not hesitate to do this with a 4L80E any time. Key to success is to keep it cool, and auxillary coolers are a must, but just as important, the ability to lock-up the converter while towing. I see temps vary over 50 deg while towing out of OD, and no lock-up.
MAybe try a gauge on the trans, and you will see what I mean. If you have been towing 6K lbs on a stock cooler, and running without lock-up, I believe you will experience this problem again unless it is addressed.
Just a thought.

Again, guess I am just venting, because I expected this 3/4 ton truck to pull #6000 easily as it has a #7100 tow rating. I also have taken excellent care and maintenance of this truck.

Now the repair tech could be blowing smoke up my butt on whats wrong with the transmission. Transmission works proper in all gears, but it will kick out of OD on a hill and then not shift back into OD. When this happens, transmission shifts hard until I stop, turn off ignition for about 15 sec. Then restart and all is fine until you get to the next hill.

Repair tech said he did not think anything was wrong with transmission as fluid was clean and no burned smell. That's why he said the torque converter was piston was busted/cracked, etc: I was losing hydraulic pressure and this low pressure would not let torgue converter lock up.

Does this reasoning sound proper or am I still going to be walking after I get this transmission back with new torque converter?

75K30 · 03-09-2008, 09:57 AM

Again, I can apprecieate the frustration with a transmisssion that operates poorly, or at least one that does not meet your expectations.
I would be very interested to have a diagnostic computer hooked up to the truck during this operation, and see in real time what is going on, while it is going on.
without the aid of the transmission controller / computer to tell you what is going on, anything (though probably very educated) might be speculation, or maybe even a wild **** guess.
Again, your technician might be right. There is a dighram responsible for the lock-up, and this could have a crack, but this would not explain why the problem will go away. The crack is still there right? I would think that a hard component that has failed, is either working or it is not, and would not repair itself when the truck is shut down for a little bit of time.
One could argue that the crack becomes worse when heat is applied, but waiting a few minutes with the engine off would not allow the fluid in the converter to cool enough to support this theory.
I cant say for sure, but I am leaning towards a simple solenoid problem, or controller problem. Your 4L80E has these shift solenoids that are external and do not even require the pan to be dropped. They are very inexpensive and can cause some real problems if not addressed. Might not be this simple, but a true, real time diagnostic will tell you.

stelmadl · 03-09-2008, 11:19 AM

I've had my 98 since day one....the transmission has not skipped a beat. I currently have over 120k miles that's seen sand dunes, travel trailers (30ft), and tree trunk removal. The hardest abuse being the dune buggy I had to pull out going uphill with 4 low engaged, last year, and the other would probably be pulling trees (12in diameter size) with chains up a hill...again, only way I could do it was with 4-low and the tires screaming...never thought you could hear tires scream when on dirt! BTW, I've changed my transmission fluid according to the manual.

03-06-2008, 08:04 PM	#1
fbhart@wk.net Senior Member Join Date: Mar 2007 Posts: 90	4L80E Transmission Problem I have a 2000 Chevy 3/4 ton, 350 engine (255 hp, 330 # torque) with a 4L80E transmission. Transmission serviced at 60K. Spec said it would tow 7100#, but believe me it cannot even tow 6000# without breaking down. The piston cracked in the torque converter at 78K miles. This truck has never pulled over 6000# and that was few times, even then it was always pulled in thrid gear, never in OD. The truck is down getting a new troque converter installed and general transmission review. This transmission must be weak, I cannot believe GM would place this transmission behind a diesel engine truck. Just venting, I thought I had bought enough truck to do the job. Guess I should have gotten a Dodge diesel with manual transmission. Should have figured it out, cars have automatics and trucks have manuals.

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03-07-2008, 01:40 AM	#2
75K30 Senior Member Join Date: Jul 2006 Posts: 2,627	Too bad about your mis-fortune with regards to your trans. However I have to completely disagree with,,,,well, about everything you have stated about the 4L80E. This is a great transmission, and is extremely reliable, and plenty capable of surviving small loads like 6,000 Lbs. I am a little fuzzy on this piston that failed in the converter. I can only assume that the converter piston responsible for the lock-up of the converter itself. This can fail for many reasons, and proably not a result of towing. As a matter of fact, towing in OD for newer transmissions is not only a decent idea, but often recommended to keep the transmission cool. You could have overheated the transmission and created a problem with the lock-up clutch itself, or even made the dampening spring fail. If this fails, the torsional force applied upon clutch engagement will promote shock transfer, and failure will result. This will occur whether or not you have a trailer, and rear axle gear selection is really very critical here. Have you changed the rear axle ratio by any chance? Lower ratios are far superior for transmission life than a highway gear, especially when small engines and trailers are thrown into the equation. I hate to hear of any unfortunate failures, and in this case it sounds rather unfortunate, but I believe you have been dealing with a damaged trans for a little while, and this is probably due to a variety of factors, and not directly related to the design of the 4L80E. FWIW, I have pulled (on several occasions) a 3 axle, 36 foot toy hauler (over 10K lbs) with a Big block, and a 4L65E. (no correction needed, it is a 65, not a 60, although they are almost identical, and still much smaller than a 4L80E.) Have pulled this trailer on many trips loaded to the gills, with not a single transmission related issue.. I would not hesitate to do this with a 4L80E any time. Key to success is to keep it cool, and auxillary coolers are a must, but just as important, the ability to lock-up the converter while towing. I see temps vary over 50 deg while towing out of OD, and no lock-up. MAybe try a gauge on the trans, and you will see what I mean. If you have been towing 6K lbs on a stock cooler, and running without lock-up, I believe you will experience this problem again unless it is addressed. Just a thought.

03-09-2008, 09:57 AM	#4
75K30 Senior Member Join Date: Jul 2006 Posts: 2,627	Again, I can apprecieate the frustration with a transmisssion that operates poorly, or at least one that does not meet your expectations. I would be very interested to have a diagnostic computer hooked up to the truck during this operation, and see in real time what is going on, while it is going on. without the aid of the transmission controller / computer to tell you what is going on, anything (though probably very educated) might be speculation, or maybe even a wild **** guess. Again, your technician might be right. There is a dighram responsible for the lock-up, and this could have a crack, but this would not explain why the problem will go away. The crack is still there right? I would think that a hard component that has failed, is either working or it is not, and would not repair itself when the truck is shut down for a little bit of time. One could argue that the crack becomes worse when heat is applied, but waiting a few minutes with the engine off would not allow the fluid in the converter to cool enough to support this theory. I cant say for sure, but I am leaning towards a simple solenoid problem, or controller problem. Your 4L80E has these shift solenoids that are external and do not even require the pan to be dropped. They are very inexpensive and can cause some real problems if not addressed. Might not be this simple, but a true, real time diagnostic will tell you.

03-09-2008, 11:19 AM	#5
stelmadl Senior Member Join Date: Nov 2005 Location: Grand Rapids, MI Posts: 103	I've had my 98 since day one....the transmission has not skipped a beat. I currently have over 120k miles that's seen sand dunes, travel trailers (30ft), and tree trunk removal. The hardest abuse being the dune buggy I had to pull out going uphill with 4 low engaged, last year, and the other would probably be pulling trees (12in diameter size) with chains up a hill...again, only way I could do it was with 4-low and the tires screaming...never thought you could hear tires scream when on dirt! BTW, I've changed my transmission fluid according to the manual.