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4L80E problems

bigirondog
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bigirondog Enthusiast

bigirondog

Posted
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Posted (edited)

I don't believe its the temp being to high.......I did block the cooler to raise the temp but no change.......being unblocked and cool to the touch plus in 30deg weather it still does it.........

the trans is running cool....

Edited by bigirondog
  • 4 weeks later...
5Alive Enthusiast

5Alive

Posted
Posted

If the trans is overheating, why would there be a strategy to unlock the torque converter when cruising down the highway? Wouldn't unlocking the converter put more drive pressure on the fluid, creating more heat? If so, I don't understand the reports where people said the dealership replaced the TC due to overheating, and when they experience overheating, the trans strategy was to create more heat.

 

I do believe the posters when they say that whatever the dealer replaced remedied the problem. I just have a hard time understanding the reason given for why?

warrab Enthusiast

warrab

Posted
Posted (edited)

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.

 

 

.

 

Mine does exactly the same thing. Doesn't matter what the temp is, loaded or running empty. Seems like 65 mph is the magic number to get it

to lock again. It's done it ever since I've owned the truck. I gave up on trying to find the problem

Edited by txab
  • 7 years later...
swilson143 New Member

swilson143

Posted
Posted

Anyone come up with a solution for this? I have a 1991 Suburban v2500 with 4L80E. At around 75 mph the torque converter begins to lock and unlock every couple seconds.

If I drop my speed back below 70 it stays locked again

Sent from my Pixel 4 using Tapatalk

swilson143 New Member

swilson143

Posted
Posted

I was experimenting with the issue on my commute home. I found that (at least on level ground) the issue occurs only between 72-75mph. Once I exceeded 75 the TC locks up and behaves normally again

I wonder if the TPS could have a bad spot in it that would cause the tranny to get a bad reading and not know the throttle position. Maybe that would cause it to think I was off the throttle for a sec and take the TC out of lockup?

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