Mid season update on our Subs 4l80E. I have taking the truck to a shop at the beginning of the season for hot towing concerns and given a clean bill of health. I have figured out why and which RPMs to be at to effectively control the TQ. This past weekend we camped in the Catskills, NY and had no spikes climbing north. The ride home was A-0k at 190 to 220F.enter NY thruway south with sluggish traffic 45 to 52mph, tow haul on, and i watched the gauge spike to 300 and then the hot trans light came on. I stopped the truck for 40 minutes and continued home for 2 more hours at 190F.i called a new shop and they feel the factory cooler is blocked. I can not believe that the 4th gear sluggish event is enough to roast the fluid. Is it something else?We are barely towing a full height trailer 7ft 6"w by 9ft 6" tall w/ac.Will adding an auxilliary cooler, and cap off factory cooler be merely a bandaid or final fix to the old school 4l80E?

The two times I had heating problems it turned out to be the fan clutch. Eventhough it seemed fine, once I replaced the clutch the heating problem went away.I also added Royal Purple "Wetter Water". It helped keep the temp from rising on 6 to 10 % grades when towing.

It might be you had enough load on the tranny in 4th gear so the torque converter would not lock up causing additional heat.

Are you towing in 4th gear or 3rd? I ask because your post makes it sound like you are towing in 4th. That's bad at any speed with the older 4 speeds. With the 4 speed, TH mode only changes the shift pattern from a dead stop. It doesn't control the shifting between 4th and 3rd or prevent OD from being used. OD kicks in at 40 so if you are in 4th and going between the speeds you were it doesn't surprise me that it heated up. At those low speeds it doesn't take much of a speed change to force it to downshift into 3rd. Constant shifts between 3rd and 4th and back again will generate a lot of heat. Are you using Dex VI when you do a fluid change? It's recommended for your truck even though it had Dex III in from the factory. Dex VI came out in 2006. Its a synthetic blend and runs far cooler than Dex III did. A trans can take short bursts above 220 without permanent damage. But 300? I dunno. That's a scary high temp.EDIT: If you add an auxillary cooler, don't bypass the factory cooler, put it inline.

Yikes. I think I'd budget for a replacement. 300 is hot. It's easy to flow test the cooler (bucket and a stopwatch) so if the shop *thinks* it's plugged due to the temps, without doing a flow test, take it elsewhere. Chasing symptoms gets expensive.

HOT 300 degree 4l80E | Good Sam Community

24 Replies

GeoBoy
Explorer
Jul 29, 2014
After the install of a Tru-Cool 40K transmission cooler 175 degrees is the max temp I saw towing in the Rockies. Over 10,000 miles towing with this cooler and no problems.
BurbMan
Explorer II
Jul 28, 2014
My 4L80E has run continuously at 175 empty and 200 towing since it was new. It only spiked briefly to 275 ONE time, which was immediately followed by complete and permanent loss of reverse. Now I have a rebuilt Jasper unit and it runs just like it was new, same temps. I got 150K miles on mine before it toasted. Now would be a good time to sign up for Good Sam roadside assistance if you don't have it already, before you take that 6 hr trip towing. I hope it turns it out to be fine, but if it's not it pays to have a plan B. FYI, Jasper unit was about $3500 installed.
PAThwacker
Explorer
Jul 25, 2014
I have a 6 hr total pull coming on on Aug 8th. I will report whatever peculiar happens. This is a 2 year odysee of high temps on our 4l80. The previous weeks hi temp was the highest and actually triggered the high trans temp warning light.
Norskeman
Explorer
Jul 25, 2014
Change the tranny fluid. Drain and refill. Run about 100 miles. Drain and fill again. This will help flush the torque converter. I would go to a synthetic TES 295 fluid.

I have an Allison - transmissions generally work OK at 220F but can go to 330F intermittant.

TES-389 and TES-295 are both transmission fluid specifications. TES means "Transmission Engineering Specification".

TES-389
The TES-389 specification required that the fluid to be tested to neet GM standards. This meant that it had been approved by General Motors to carry the DEXRON registered trademark. GM is now using DEX VI

TES-295 (synthetic)
The TES-295 specification is a complete specification that includes a whole bunch of different tests. It was designed to test fluids and only approve the ones that showed the following exceptionally good fluid properties:
Oxidation Resistance
Viscosity Stability
Seals Compatibility
Wear Resistance

TES 295® Approval Number / Approved Marketer / Product Brandname

AN-011001 Castrol Heavy Duty Lubricants---- TranSynd
AN-031002 BP Lubricants---- Autran Syn 295
AN-031003 BASF Corporation---- Emgard 2805
AN-031004 International Truck & Engine Company----Fleetrite Synthetic ATF
AN-051005 ExxonMobil Lubricants and Petroleum Specialties Co---Mobil Delvac Synthetic ATF
AN-071006 John Deere & Company---- HD SynTran
AN-1010007 Mack Trucks, Inc ----Bulldog Synthetic ATF
AN-121009 Case New Holland---- CNH HD Synthetic ATF
AN-121008 Shell International Petroleum Co. LTD.----Shell Spirax S6 ATF A295
PAThwacker
Explorer
Jul 25, 2014
22 quarts of synthetic later. No chunks of metal, or other tell tale signs. No trans mission codes nor shifting trouble.

I am hoping its A-OK, allegedly the front to back fluid change was done when purchased. I am starting to question that bill of goods.
PAThwacker
Explorer
Jul 25, 2014
The truck runs all day at 190, climbs a hill, and gets hot, cools down on the other. Slugging in traffic and the temps hit the roof. I hope its only a fluid issue.
PAThwacker
Explorer
Jul 24, 2014
It is strange and has been going on for the past 2 seasons. 2 more hours on the trip and the trans was at 190. I am getting new fluid, and will try towing it again in a week.
Turtle_n_Peeps
Explorer
Jul 24, 2014
PAThwacker wrote:
Fluid looked metallic at the belly of the pan. cooler lines were not blocked New tow vehicle shopping as I type.

At 300 degrees this is not shocking. Some kind of hard parts failure.
PAThwacker
Explorer
Jul 24, 2014
Fluid looked metallic at the belly of the pan. cooler lines were not blocked New tow vehicle shopping as I type.
Hybridhunter
Explorer
Jul 22, 2014
Keep that thing cool bud, replacing these things is a fleet ritual around 85K miles for us.......
And I agree with a previous poster, check the fan clutch, and make sure the "chin spoiler" under the from bumper is there, it makes a difference!