4L80E running hot

Well, still chasing things down to no avail. After burning my arm on the exhaust and the t-case at the same time last weekend, I felt like the exhaust could be causing extra heat to build up in the transmission. So I spent some time with some exhaust wrap and covered the entire pipe from where it crosses in front of the tranny, till about midway on the t-case, including the cat. Drove home like normal, and it seemed to help ever so slightly in the around town portion, but really made no difference. I was quite disappointed, because I really felt like I could be onto something.

Then I tested the airflow to the coolers by putting a piece of paper in front of them. Radiator, AC condenser, and Hayden cooler all held the piece of paper tight. The factory auxiliary cooler didn't have as much pull (but it is like 4" from the radiator with 3 gaps...). So I made up some awesome cardboard shrouding, that covered almost the entire inside of the grill and 50-60% of the radiator, and routed all that air to the cooler. That made the paper stick to the factory cooler very strongly. Took it for a test drive, maybe helped a little, but nothing measurable.

Also, took some more readings on the lines:
Temp gage 240, cooler supply 230, cooler return 130, pan bottom 150, pan top 235ish (pre-cardboard shroud, after driving 30 minutes, 15 miles interstate, 2 miles town, 10 miles country roads)
Temp gage 220, cooler supply 220, cooler return 120, pan bottom 150, pan top 230ish (post-cardboard shroud, after driving 10 minutes, 10 miles country roads, was already hot, but cooled down to 200F first)

So it looks like the cooler is doing it job, but something is still putting major heat into the fluid.
 
jeepinmatt said:
Well, still chasing things down to no avail. After burning my arm on the exhaust and the t-case at the same time last weekend, I felt like the exhaust could be causing extra heat to build up in the transmission. So I spent some time with some exhaust wrap and covered the entire pipe from where it crosses in front of the tranny, till about midway on the t-case, including the cat. Drove home like normal, and it seemed to help ever so slightly in the around town portion, but really made no difference. I was quite disappointed, because I really felt like I could be onto something.

Then I tested the airflow to the coolers by putting a piece of paper in front of them. Radiator, AC condenser, and Hayden cooler all held the piece of paper tight. The factory auxiliary cooler didn't have as much pull (but it is like 4" from the radiator with 3 gaps...). So I made up some awesome cardboard shrouding, that covered almost the entire inside of the grill and 50-60% of the radiator, and routed all that air to the cooler. That made the paper stick to the factory cooler very strongly. Took it for a test drive, maybe helped a little, but nothing measurable.

Also, took some more readings on the lines:
Temp gage 240, cooler supply 230, cooler return 130, pan bottom 150, pan top 235ish (pre-cardboard shroud, after driving 30 minutes, 15 miles interstate, 2 miles town, 10 miles country roads)
Temp gage 220, cooler supply 220, cooler return 120, pan bottom 150, pan top 230ish (post-cardboard shroud, after driving 10 minutes, 10 miles country roads, was already hot, but cooled down to 200F first)

So it looks like the cooler is doing it job, but something is still putting major heat into the fluid.
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I also have a 2005 gmc with a 4l80 mines two wheel thow anyway it was just rebuilt and new torq converter I ran it for 10 min if that. And it's at 210 the tranny yes it has fluid but I have not checked nothin else yet it just happened 10 min ago and I was woundeding what did u do on yours to fixes it prior to my rebuild it never got that hot especially that fast
 
Never figured it out. As far as I know, neither did the guy I sold it to. @Blaze did you create a fake account just to bump this thread? :lol:
 
jeepinmatt said:
Never figured it out. As far as I know, neither did the guy I sold it to. @Blaze did you create a fake account just to bump this thread? :lol:
Click to expand...

No way, that truck has been banished from my memory. Only vehicle I ever lost money on. :lol:
 
Did you flush the heat exchanger and external cooler (if it has one) ? The heat exchangers in the radiator usually catch all the crap in them. Best bet is replacing the radiator.
 
Croatan_Kid said:
Did you flush the heat exchanger and external cooler (if it has one) ? The heat exchangers in the radiator usually catch all the crap in them. Best bet is replacing the radiator.
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BY passed the radiator completely (per the builder's recommendation) and added a new 30k cooler in front . I've read a lot about overheating trans after rebuilds but not finding anyone who finds the cause. So many end up trading the trucks.
 
I think keeping it running through the radiator is generally a good idea to help regulate temps. Helps it warm up faster, but will also draw heat out if it gets tooo hot.
 
Blaze said:
In my experience, the best way to fix the problem is to sell the truck and get one that the transmission doesn't overheat on.
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I'll second that motion :laughing:
 
My former truck was a 98 Silverado 1500 Z-71. 5.7 Vortech, 4L60. Mobile 1 syn atf, & sold at 110,000. Towed my trailer & CJ, many a time, & never had a problem. Had no idea what the temps were. Now my 2016, 1500, 4x4, 6.2 & 8L90, has the info cluster that will dial up the tranny temp. I tow heavier trailer & CJ, up Fancy gap, on cruise control, at 60 mph. Engine stays a constant 210, & tranny runs 170 -175. That's one Hell of a Cooler!
 
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