Truck overheating towing on long steep grades.

[mike-uswest]

The other day I came out of Death Valley to Beatty which is long and steep, but not that bad, but the transmission temp got up to 230 for most of the trip. I stopped part of the way up and let it cool before going on. This has happened a few time in the past, but I am looking to add a additional cooler if for nothing else make me more comfortable. The truck is a 2003 Dodge Cummins with less than 160,000 on it, and runs great. I would like to find an add on cooler that would not cost a mint and be an easy application to take care of this in the future. I have had it 15 years and other than this it has been a great truck. There doesn't seem to be a lot of room with coolers attached to the radiator now. Anyone have any suggestions? Thanks, Mike.

[Cummins12V98]

I always towed by the pyrometer on my 98 12V. Lots of pedal left but all I would have done was burn up #6.

[time2roll]

I agree dropping one more gear and running part throttle and keeping the RPM up is the best plan if the temp gauge is rising uncomfortably. Generally I recommend RPM between peak torque and peak HP when pulling max.

For an older truck it might be worth while to replace the radiator. And if the TC does not lock in second and this is an option to fix with a chip I would go for that. Just don't use the chip to make more power as that can only make things worse. I don't recommend anything that would defeat emission controls.

[Grit_dog]

SweetLou wrote:
This maybe an ignorant question, but when I had my '97 and '05 cummins, I monitored my exhaust temps closely. If I stayed at 1000 to 1100 degrees and no higher, I could climb any grade at any tme without heating issues. I had a manual trans in both, and I realize that this is not the same animal that the OP is asking, but trans temps are related to how much you have your foot in the truck as well right? Gear down, get the fan to spin higher, and it just goes. 16 miles of the Baker grade at 117 degrees outside was never an issue even with windows open. Like I said, I may not be correct here, but if I am, then possibly adding an exhaust temp gauge is all that is needed along with cleaning the coolers.

EGT gauge is handy, albeit unnecessary for a stock truck.
I'll presume your statement above, the 1000-1100 degrees is a post turbo EGT? If it's preturbo temps then you were limiting your right foot input to about half the safely available output.

[ppine]

On steep roads like going to Death Valley your engine and your brakes are going to get hot when towing. Get used to it and pull over.

[Cummins12V98]

100% agree! Drop a gear and back out of the throttle, does wonders.

[SweetLou]

This maybe an ignorant question, but when I had my '97 and '05 cummins, I monitored my exhaust temps closely. If I stayed at 1000 to 1100 degrees and no higher, I could climb any grade at any tme without heating issues. I had a manual trans in both, and I realize that this is not the same animal that the OP is asking, but trans temps are related to how much you have your foot in the truck as well right? Gear down, get the fan to spin higher, and it just goes. 16 miles of the Baker grade at 117 degrees outside was never an issue even with windows open. Like I said, I may not be correct here, but if I am, then possibly adding an exhaust temp gauge is all that is needed along with cleaning the coolers.

[LITEPHIL]

That's probably nothing to worry about at all. I've towed the same hills here in Arizona for many years and EVERY one of my trucks temp would go 3/4 the way up and the transmissions would go to at least 230 on the long climbs. That's another reason to use synthetic fluids. On my 06 Dodge Cummins I did install a Mag-hitec deep transmission pan to be safe.

[garyp4951]

The 2003 5.9 Cummins had an additional torque converter cooler mounted on the driver side at the rear on the engine, and I would check this also.
As stated before, replacing the vicious fan clutch with only oem did the trick for me.

[Cummins12V98]

Someone besides me please confirm but the 3rd gen 4 speed auto does NOT lock in 2nd???

I know it can be made to be.

[FishOnOne]

time2roll wrote:

Cummins12V98 wrote:
If you were doing 35 you were unlocked in 2nd gear!

No lock in second gear? That seems like bad design to me.

The entire life span of the torqueflite was a bad design

[Grit_dog]

time2roll wrote:

Cummins12V98 wrote:
If you were doing 35 you were unlocked in 2nd gear!

No lock in second gear? That seems like bad design to me.

Bad design? It's in a truck that is old enough to have it's own driver's license and based on a transmission that is almost old enough to join AARP.
Not a bad design, just old technology. It's actually a great design, just a bad application by Dodge to use that trans in the 21st century!

(Since you're not saavy with this, the 47/48re transmissions are still the preferred units for extreme loads like drag racing and truck pulls. Just not a good on the road application based on the current technology available in the early 2000s.)

[time2roll]

Cummins12V98 wrote:
If you were doing 35 you were unlocked in 2nd gear!

No lock in second gear? That seems like bad design to me.

[ppine]

This conversation is between people that have never been on those roads.

My Ford 7.3 is in great shape, but I still had to pull over to cool off the engine and brakes when pulling a trailer in these hills.

[Grit_dog]

Mike, to 12Vs point, a manual torque converter lockup switch is a great addition to your truck to improve efficiency and reduce trans temperatures.
If you've driven any newer trucks, especially towed with them, you realize that the 4 speed auto is basically the Achilles heel of the 3rd gen Cummins trucks.

Before the ram Mafia jumps in, yes, it's a very simple and fairly reliable transmission, but due to only having 4 gears, you have to drive around the trans sometimes when towing.

Either way, deep finned pan and mystery switch are the 2 best easy basic mods you can do to a 48re for towing.