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4L80E problems

bigirondog
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bigirondog Enthusiast

bigirondog

Posted
Posted

I have a 06 GMC 2500HD 4x4 6.0 4L80E 4:10.. 85,500 milage.....

 

my issue is the torque converter will unlock at random at about 70 mph.

I can pull a trailer with a heavy load and stay under 70 mph and all is great. power is good. however with NO load and level ground the torque converter unlocks and will not lock back up until I slow down to below 65 mph.

 

NO CODES.....

I have extra parts from other trucks to which I have changed the throttle position sensor, throttle body, ECU on the firewall under the hood, and the torque converter lock up in the trans. also changed the fluid, added lucas all with no change.

it takes it a long time to lock up when its cold, first thing of a morning.

 

this truck does great under a load or empty as long as I stay below 70 mph.

using the cruise or with out, no change.

 

any suggestions as to where to look and what at would be great.

 

 

 

Grumpy Tooch Enthusiast

Grumpy Tooch

Posted
Posted

@ about 75000mi I had problem with my tranny over heating. I had to have the TC replaced, along with all the lines too. They told me it was common with 4l80e

bigirondog Enthusiast

bigirondog

Posted
  • Author
Posted

I have owned it since 45,000 miles......I never drove it on the interstate or got above 70 until a year ago.

 

the temp guage never gets hot, trans seems to run cool. I replaced the stock cooler with a larger trans cooler.

 

it does this when its cold also. first thing of a morning takes a long time for TC to lockup.

ZachM1 Enthusiast

ZachM1

Posted
Posted

I had a similar issue with my 4l80e. Put a larger cooler on it and the same thing happened.

There is a temperature sensor in the transmission. When the trans fluid goes below a certain temp, torque converter lockup is canceled. When the temp goes above that temp, it is re-enabled.

When your torque converter is in lockup mode, the transmission is in a "cooling and overdrive planetary lube" mode.

 

With the larger cooler it is going below the temperature range that allows this when in lockup.

 

Not going into lockup with the 4l80e due to over cooling will not damage anything. It will just affect your mpg.

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted (edited)

I had a similar issue with my 4l80e. Put a larger cooler on it and the same thing happened. There is a temperature sensor in the transmission. When the trans fluid goes below a certain temp, torque converter lockup is canceled. When the temp goes above that temp, it is re-enabled. When your torque converter is in lockup mode, the transmission is in a "cooling and overdrive planetary lube" mode. With the larger cooler it is going below the temperature range that allows this when in lockup. Not going into lockup with the 4l80e due to over cooling will not damage anything. It will just affect your mpg.

 

 

what ?,where did ya get that info ? i must check my blue book if i can find it lol

Edited by govtech4
ZachM1 Enthusiast

ZachM1

Posted
Posted

 

 

what ?,where did ya get that info ? i must check my blue book if i can find it lol

 

Oh just being a transmission specialist / rebuilder for well over a decade.

scooby5121 Enthusiast

scooby5121

Posted
Posted (edited)

Mine always unlocks on hills, pulling or not.

Scooby

 

Hot or Cold.....

Edited by scooby5121
Badass69 Senior Enthusiast

Badass69

Posted
Posted

Yeah but locking and unlocking at random is not normal. The most annoying thing I found was the wide open throttle lockup in 2nd gear that the 80E's do.... dumb. So neither of mine have that ability anymore lol.

 

I was convinced my 04's transmission was toast. My convertor would lock and unlock at random.... wouldn't unlock properly etc. Then the trans itself shifted really hard ( line pressure was maxing), hang up in gears etc... I had no codes, nothing that really stood out. So because I have parts I swapped the 3 things one at a time enginewise I thought it could be, being my throttle body ( so I got a known good tps), map sensor and MAF sensor. Low and behold it was my MAF... Now I have scanning software and I had very odd fuel trims at idle, random knock retard at WOT etc. The truck ran well enough and never did anything weird that without seeing the data no one would have noticed the engine issues ever.

 

It's worth a look anyhow. I have had a check engine light or anything either, and if the OP has parts to swap since you tried the throttle body give the mass airflow and map sensors a try.

  • Like 1
97CAIVIAROSS Enthusiast

97CAIVIAROSS

Posted
Posted

I didn't have the exact same symptoms as you but mine would lock then unlock and not lock again on the highway. Did some reading on this site and the solution to mine was a crank position sensor relearn. Did they with a SnapOn scanner believe it was a Modus and all is good now.

Grumpy Tooch Enthusiast

Grumpy Tooch

Posted
Posted

I have a 06 GMC 2500HD 4x4 6.0 4L80E 4:10.. 85,500 milage.....

 

my issue is the torque converter will unlock at random at about 70 mph.

I can pull a trailer with a heavy load and stay under 70 mph and all is great. power is good. however with NO load and level ground the torque converter unlocks and will not lock back up until I slow down to below 65 mph.

 

NO CODES.....

I have extra parts from other trucks to which I have changed the throttle position sensor, throttle body, ECU on the firewall under the hood, and the torque converter lock up in the trans. also changed the fluid, added lucas all with no change.

it takes it a long time to lock up when its cold, first thing of a morning.

 

this truck does great under a load or empty as long as I stay below 70 mph.

using the cruise or with out, no change.

 

any suggestions as to where to look and what at would be great.

 

 

 

I have the same truck same mileage and I had the same problem 6 months agohad to have the dealership replace a torque converter and all the lines going to the raditormy issue was is that the transmission was overheating

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