4L80E running hot

jeepinmatt

jeepinmatt

..l.
Joined
Mar 24, 2005
Location
Stanley, NC
I had the 4L80E in my truck rebuilt after a major planetary failure. Now it runs in the 200-220F range with no load and no trailer under normal driving. If I keep the rpm's down (try to stay under 2000 everywhere), it will run more in the 150 range. But once it starts heating up, it doesn't cool down. It is equipped with the through the radiator cooler and the small factory external cooler. I just added an 11x11x3/4" cooler this weekend hoping it would make a difference, but it didn't really seem to (maybe 5 degrees). On hot days, it will start getting up in the 240-250 range around town, easy driving. I've verified the temps with a known good thermometer, and the gauge is correct.

There are no check engine lights, speedo works, torque converter is locking and unlocking appropriately, and the tranny shifts normally and correctly (except for a delayed shift from 2-3 when cold). I'm suspicious that its something pump related since higher rpms lead to higher temps, regardless of airflow on the coolers.

Anybody got any insight?
 
I don't have a scanner, I'll see if I can find someone around here. I know Matt (RHSCTJ) has a scanner, but I don't know how much it can read off the tranny.

The pump was not replaced when it was rebuilt. The damaged parts were replaced, and then a "standard" rebuild was done (just clutches, bearings, seals, I believe).
 
IIRC the ttc lock up was working correctly when I scanned it initially. And the converter itself seemed to have a pretty tight stall. Did you ever get the stalling issue resolved? I could bring my scanner back up there...I need to shorten my front d shaft and I like what you did with that red tj. Although Im not sure you got your moneys worth last time we bartered, lol. 3 hours and all I could figure out was there was a broken wire. Couldnt even find it!
 
there is a difference between the lock up working and the slip. i don't know what kind of scanner you have but there should be a pid where you can watch converter slip in real time.
the tcc can work and the converter could still have too much slip.
 
My scanner is a OTC genisys with relatively new software. It was several weeks ago and I was trying to figure out why the speedo didnt work. It will record all the trans slip data, we just didnt at the time. Help me out because im a little confused. Are you saying the tc clutch is slipping and causing it to heat up the trans fluid? Wouldn't that cause a noticable shudder? Or a problem with the converter unlocked?
 
Matt, last time you were up here, I didn't have the Trans Input Shaft Speed Sensor connected or Trans Output Speed Sensor or the VSS. Now they are all corrected and working properly, and all of the problems are fixed except the overheating.
 
RHSCTJ said:
My scanner is a OTC genisys with relatively new software. It was several weeks ago and I was trying to figure out why the speedo didnt work. It will record all the trans slip data, we just didnt at the time. Help me out because im a little confused. Are you saying the tc clutch is slipping and causing it to heat up the trans fluid? Wouldn't that cause a noticable shudder? Or a problem with the converter unlocked?
Click to expand...


no, it isn't the clutch that you need to check.
the clutch will have a % of apply, as long as that reaches 100% that is not the issue. the sprag in the converter is what i'm referring to. you will find a pid for converter slip, it will be seperate from tcc.
another thing to watch is rpm vs. input speed sensor. if you graph them you should see that they run together, if one jumps higher than the other you either have slip in the converter or input clutch.

on the converter slip, if it is above 150rpm slip it's creating too much heat (i'm not sure of the exact number but a 4l60e anything over 150 rpm slip sets 1870 codes, i wouldn't think their programming allows for much more than that)
 
was the cooler flushed? (in the radiator)
the problem could very well be in the cooler also, if it is restricted it will not have the proper cooler flow. you may want to try bypassing the cooler in the radiator and see if it still does it. also check to see if it has an inline filter anywhere.
 
transman731 said:
was the cooler flushed? (in the radiator)
the problem could very well be in the cooler also, if it is restricted it will not have the proper cooler flow. you may want to try bypassing the cooler in the radiator and see if it still does it. also check to see if it has an inline filter anywhere.
Click to expand...
I flushed the cooler and the lines. There is no inline filter. I did not flush the tank in the radiator, but I had no trouble with flow in one line and out the other in either direction.
 
jeepinmatt said:
I flushed the cooler and the lines. There is no inline filter. I did not flush the tank in the radiator, but I had no trouble with flow in one line and out the other in either direction.
Click to expand...

the problem is that when the cooler in the radiator gets hot it contracts and causes restriction( not saying that's the issue but it normally is a hot issue when it's cooler flow)
 
here is what your cooler looks like in the radiator

ai218.photobucket.com_albums_cc317_putzarerequired_2010_02_10161501_1.jpg


ai218.photobucket.com_albums_cc317_putzarerequired_2010_02_10161546.jpg


ai218.photobucket.com_albums_cc317_putzarerequired_2010_02_10161626.jpg
 
Hmmm. Not real inspiring. I may see if I can find a way to bypass the radiator cooler since I know the other one is good. I'd think 14.5qts of fluid and a small cooler should be more than enough for normal, easy driving.
 
jeepinmatt said:
Hmmm. Not real inspiring.
Click to expand...

Honestly, that's "huge & efficient" compared to most (a 3/8" tube that *might* have a small loop in it)... before the tube splits, injects water into the circuit and cooks your tranny. Without starting a shitstorm of varying opinions about them (I personally think they're worthless as coolers, but may have merit as "heaters" in sub-zero clims), I've bypassed the radiator with every auto I've owned...
 
I've tried a few things in the past couple of days. The first thing was to bypass the cooler in the radiator. It made no difference. Next, I verified flow from the transmission into a 5 gallon bucket. I would guess it pumped 1.5qts in 10 seconds, but seemed like plenty. Then I bypassed the factory trans cooler and left the radiator bypassed also, so that the only cooling was from the Hayden 10k auxillary. Still made no difference. After a 30 minute spirited drive, the trans temp gage was showing 240F when I pulled in the driveway. That seemed crazy, so I pulled out the (somewhat) trusty infrared thermometer, and got the following readings:
Aux cooler ~100-110, but its shiny so readings are unreliable
Trans pan 155-160
Trans to cooler line 160ish
Cooler to trans line 120ish
Engine block 180
Exhaust 300ish
Other surfaces that should be at ambient were within 5 degrees, so I feel pretty good about the numbers. Makes me think the gage is off. I've checked it before when it showed 160ish and the pan also showed 160ish. But it seems to just keep climbing once it reaches 180, regardless of how hard or easy I am on the tranny.

Thoughts? RHSCTJ is coming over tomorrow with his scanner, so we will see if the internal temp sensor is working correctly. Is the pan temp a good indication of operating temp?
 
Did a little more testing and measuring tonight, radiator cooler bypassed and factory aux cooler bypassed.
Gauge at 200, pan was reading 140-150ish on the bottom, closer to 180 at the top where it meets the trans case.
The line from trans to cooler was 180ish, from cooler back to trans was 135ish.

I then reconnected the factory cooler, it sat for a while, and I drove home. Got it heated up to about 150 on the gauge.
Pan was at 115 at the bottom and 150ish at the top edge.
Trans to cooler was 100ish, return line was 85-90.

I don't know if any of this is helpful, but the data is captured...
 
I'm no expert but I had my 2wd, 4.3, S10s 4L6oe's tranny rebuilt last year and the builder told me to add an auxillary cooler cause i was having engine overheating issues while towing a 2500lb +/- boat on hot days before the tranny blew a gonad. He ordered a Hayden unit I easily installed infront of the rad. He said it would make the tranny last longer than the rest of the 98 truck w 150k. It seems to do fine now on hotter days though i'm not sure if it would help at low 4wheelin speeds? I chose to bypass the GM factory rad. cooler, though it can be included per the instructions.
 
I went up to dallas to help matt sunday. Here's what we came up with:
-Factory rad cooler is bypassed
-Has factory external cooler and a 10k gvw aftermarket cooler
-average tc slip was about 900 under heavy acceleration
-TCC locks and has no slip
-All the lines have been removed and flushed
After 22 mins of normal driving back roads trans temp was >208*
Stopped at the parts store for more ATF with the truck running in N temp droppde to 190* in just a few minutes
20 mins more of back roads heading back to the shop trans temp hit 240* (temp at the pan with a laser was <10* different than what my scanner was reading)
ECT never got above 180*
Trans functions completely normal except its getting hot
 
at this point, i suggest taking it somewhere to have it flow tested. it really needs to be tested while you are driving. if you say that the flow is fine while at idle.
also, i would suggest a bigger cooler. a 10k is not enough in my opinion, usually i install nothing smaller than 20k coolers.
by getting it flow tested, it will tell you if it's a valve body problem or a pump issue. i don't know where to tell you to go because not every tranny shop uses them.
 
Thanks for the input, Lee. We know 10k isnt enough for the trucks intended use but It was available and should be plenty enough to keep it cool with no load right? Is there anything I can test with a line pressure gauge set? Is it just as simple as putting a gauge on the "pressure" line or are there some test ports like on a honda? Or should we throw in the towel? Hope you dont charge per question. Lol
 
transman731 said:
at this point, i suggest taking it somewhere to have it flow tested. it really needs to be tested while you are driving. if you say that the flow is fine while at idle.
also, i would suggest a bigger cooler. a 10k is not enough in my opinion, usually i install nothing smaller than 20k coolers.
by getting it flow tested, it will tell you if it's a valve body problem or a pump issue. i don't know where to tell you to go because not every tranny shop uses them.
Click to expand...
Theres a good chance I could get it to your shop in the near future...

As far as the 10k cooler, while its probably not enough, these trucks didn't come with overheating trannies from the factory. I would think that the factory cooler should keep the temps fine with normal driving towing nothing.
 
Sorry to thread jack but; How hot is too hot? Is it different for synthetic fluids?
 
I don't worry until it start going over 240. Mines just been getting or staying hot when it should be cooling down. Would probably be much less of an issue if I didn't have a gauge.
 
Back
Top