I have a 2011 Dodge Dually with Cummins engine, 6-speed automatic. When pulling a 35-foot HitchHiker 5th Wheel weighing over 16,000 pounds, at the very end of a hard climb in the mountains up to about 8500 feet above sea level, the transmission temperature light comes on. Is there something I can do to make the transmission more heavy-duty? Maybe a heavier duty transmission cooler or a larger oil pan? I only have 3200 miles on the truck.

 

Do you have the max tow package? It is an option. It includes the two piece trailer plug, the electric brake dealio and dual external transmission coolers and maybe something else I'm forgetting. If you have this option then another cooler probably won't help. If you didn't add this option then an additional cooler added to the one you get with the regular tow package would probably help. Were you using tow/haul mode? To keep the tranny happy you shouldn't pull grades with that kind of weight less than about 2200 RPM in my opinion. Sometimes you may have to use the trans in the manual paddle shift mode in order to keep it cool while being able to dictate which RPM you pull at.

Maybe some of the tranny gurus on here will chime in too.

 

I think it is the max tow. It has the two-piece electric trailer plug. Highway towing usually stays about 1800 rpm, and I have no heating problems. It's only at the top of the climb that I have the red light, and the rpms are plenty high. In 1st and 2nd gear, climbing the mountain, I'm sure the rpm is close to 3000.

 

When was the last time that you serviced the tranny and changed the oil?

 

With only 3200 miles on the odo he's only 10% of the way to his first scheduled service.

Jerry, I assume you're using tow-haul mode? My '03 used to do what you're describing. 2nd gear towing was brutal, but that was only necessary on dirt roads in the back-country, never on highways where I could always go the speed limit (only 10k lbs though). I believe it had something to do with the TC not locking up in 2nd. Not sure how the 68RFE handles slow speeds like that. I'd just pull over and let it idle in neutral for a couple of minutes, would cool right down.

Could be as simple as putting a fan on the tranny cooler if possible? Maybe it's just not getting enough airflow at those slow speeds. It's not even really summer yet...

 

Last summer we took our 36ft 3 slide Crusader around 14,000lb through the US and back into BC through the mountains. As this was the first trip with the new truck and trailer I monitored the transmission temp like a hawk as I am used to a standard trans. The truck was not deleted at the time so no transmission tune but all I can say is my temp hardly changed while towing even climbing those mountain passes. I used tow/haul the whole time and the manual paddle shift a lot, anticipating a down shift to keep rpm up. My comments would be "there's something wrong".

 

Yup, there's something wrong. I routinely 15 - 20k in the mountains and never have any problems. The tranny temp pretty much holds steady. I would get it in to a dealer and have it looked at. Might as well get it fixed while the warranty will cover it.

 

Thanks for the replys. I will take it into the dealer to check it out. I always tow in the tow/haul mode, with the engine brake on. It never gets hot when towing highway speeds, or even slowing to 30 mph on rough roads. The red temp light comes on during the last 500 to 1000 feet of switch-back mountain road, where I'm in low gear or 2nd at the most, going only a few miles per hour. At faster speeds, it pulls like a charm. Thanks for the input

 

The torque converter for the 68RFE auto doesn't lockup in first gear, which is why your transmission is getting hot. It only locks up in second thru sixth gear. Try to keep it in second gear with the converter locked, and see if your heat issue goes away.
Rich

 

If you can't get the torque converter to stay locked because you are going too slow you could try putting it in low range. It will keep the revs up and the torque converter will stay locked. It will also allow you to use the exhaust brake at a lower speed.

 

HL649, is it advisable to put it in low range and in 4 wheel drive while driving on pavement?

 

It's the same as in 4WD and high range but it's geared lower. It will hop a bit if you turn sharp but it shouldn't hurt anything. I just try not to make any sharp turns.

 

I know the truck is brand new but have you checked your tranny fluid level? These things can get overlooked during a PDI.