Towing, stock auto. transmission

[LGarcia]

I finally towed with my guages installed and was shocked! The transmission temp guage redlined even though I kept the EGT at 1200 or under, and my 5th wheel is pretty light (7,000 empty, appx 8k with the load I had). The engine temp nearly maxed as well, and I was only doing 10-15 mph.



I was on the grade between Manilla UT and Dutch John (Flaming Gorge) and by the time the temps peaked, I was past the pull-overs, so I had to keep moving. Granted, that's a steep grade, but I thought my rig would fare better.



I'm not sure what to do, would a mild EZ help (more power), or do I have to improve transmission cooling somehow (without warranty issues)?

 

[paccool]

Having just gone through a similar problem, I would guess that the engine temp is the problem and it is adding temp through the transmission cooler (if the newer trucks still use the water type transmission coolers). I had transmission temps that were tracking the water temp on the engine and it was from a bad thermostat I put in from NAPA. Saw water temps almost at the hot position and the transmission temp was about 210. Normally runs about 160-170 which is a little below the water temp reading. Picked up a new Cummins unit and installed and have not had a overheat problem since then.



Since you have a newer truck, this may not be the problem as I also wonder about the EGT readings you had. I'm assuming they are pre-turbo and not post position. Could be a timing issue or something like that. Also make sure the radiator isn't loaded with bugs.

 

[Rosco]

LGarcia, The fact your were only doing 10-15 mph could have played a role in this situation. With speeds in that range your not moving a lot of air over the radiator/ trans cooler to keep things cool. Also at that speed the torque converter probably was not locked so the resulting fluid shear of the unlocked converter will generat a LOT of heat especially while pulling a load. Add to that high outside air temps you end up with a definite overheat possibility.

 

[RustyJC]

You didn't say - was the fan clutch working? Did you hear the engine cooling fan kick in?



Rusty

 

[LGarcia]

Paccool, my truck is pretty new (and clean) so I don't think it was bugs. It runs real well in all other situations, that is just one nasty grade, especially near the top. The EGTs are pre-turbo.



Rosco, the speed issue crossed my mind, but at speeds over that the EGT was edging 1400 degrees.



Rusty, I did hear the clutch fan before that incline, and on the return home, but not specifically at that time. It didn't get that hot on the way back.



There is a pull-over about 3/4 of the way up that hill, maybe I just need to stop until everything cools down? I assume idling in park will do it? I can't imagine what problems I'd have if I had bought the heavier trailer I was looking at.



:--)



So everyone agrees power isn't the issue?

 

[Steve M]

Is your transmission temp gauge reading the temp in the hot line out of the transmission or in the pan? Hot line temps can peak pretty high and do no harm as the fluid is hot for a short time as it travels to the coolers. Pan temperature is what you're more interested in as that's the fluid that gets sucked up into the valve body and clutch packs. It doesn't hurt the fluid to get well above 200*F for very brief periods of time as it does leaving the TC on it's way to the cooler. If it's over 200*F in the pan, then I'd start looking for ways to cool it more. One thing I would do if I were you is have the fluid changed and upgraded to Chrysler ATF-4. It's full synthetic and has Chrysler's recipe for the clutches and TC clutch. A deep finned transmission pan wouldn't hurt either. Mopar's is alot less $$$ than a Mag-Hytech and works just as well.

 

[Rosco]

I am a dope! I had a brain fart when I posted earlier and I did not take into consideration the fan pulling air over the radiator.



But, I like mike fluid shear comment so I will stand by it.

 

[cwsoules]

From your post I can not tell what gear you were in. On a steep grade before I made the DTT mods I would shift to 2nd below 40 mph to keep the engine rpm up and the flow thru the transmission cooler high. Even now with transmission modified I down shift to 2nd at low speed.

 

[TowPro]

Idling in Park will not cool off the trans, From what I understand, the trans does NOT pump cooling fluid in park, but it does in every other gear. That's why you have to put it in neutral to check the trans level.

Originally posted by LGarcia



There is a pull-over about 3/4 of the way up that hill, maybe I just need to stop until everything cools down? I assume idling in park will do it? :--)



So everyone agrees power isn't the issue?

 

[RobG]

I would suggest replacing the stock trans cooler with one that has a fan built into it...



I may end up doing this myself after I get guages in my truck.



Rob

 

[LGarcia]

Thanks for all the input folks, I'm headed that way again this weekend, so I need all the help I can get.



The trans temp gage is not from the pan, probably the line out. 2002s already have synthetic fluid, but the pan is a good suggestion. I've thought about a better trans cooler which should help even though the lines are fairly small diamerter. Any suggestions as to make/model?



I was in 1st and 2nd gear, around 2000 rpm, egt temps at 1200-1300.



I'll pull over this trip before the worst of the hill and idle in neutral until things cool down.