I have a 94 dodge ram 2500 RWD with a GVW of 8800. it has a 5.9L 360 gas engine with 90K on it. I'm towing a 25' travel trailer that is 4100 empty and just over 5k loaded up. I seem to be having issues when pulling the trailer. I had the transmission just replaced a few months ago but when I'm pulling the trailer it seems like overdrive stops coming on when it heats up. Without pulling a trailer im running around 200F (195 t stat installed) but when pulling the temp goes up to 220F and OD kicks off for a while until it cools off a bit. This new transmission has like 2 ODs one that kicks in and at 65 mph it's running at 2500 RPM's and when the second one kicks in, I'll be running at 70 MPH at 2000 RPM's. So at this time I'm getting around 7mpg when pulling the trailer because of the OD issue. I've changed the T stat, flushed the radiator, replaced the fan clutch, clean out the finnes in the condenser and the radiator. It also has a large trans cooler in between the radiator and condenser. Can't seem to run it cool enough to get OD to stay on and keep the RPM's in a reasonable range. My other concern is if this truck will have enough power to pull the trailer up some of the mountain out west. Need to figure this out before trying to take a long very hilly trip with it. Any insight would be appreciated.

 

The transmission is basically a 3 speed with an added overdrive unit and torque converter lockup. Generally you should tow with overdrive off unless it's a really light trailer. The PCM disables overdrive when the transmission gets too hot, and having the TC clutch go on and off can ruin it pretty quickly. Also keep in mind that you likely have two transmission coolers in a truck like yours, one in the radiator and the additional one, so seeing the engine temp go up can be explained by the hot transmission fluid heating up the coolant in the radiator.
Having said that, you might want to check that the transmission cooler lines are hooked up correctly and not reversed. The metal line on the left goes to the lower connection of the external cooler, and the metal line on the right goes to the radiator.

 

As was stated, towing any trailer other than a light empty trailer should only be done with overdrive off. Also, please check to ensure that the transmission check valve is removed - it is in the transmission cooling line up near the radiator - https://dodgeforum.com/forum/2nd-gen...46rh-46re.html

Lastly, what size tires are you running on your truck and what is your rear end gear ratio? This can also affect your towing capabilities, especially on hills.

 

If you look in your owners manual it will say turn the OD OFF when towing. The OD unit will slip heating up the fluid and wearing the friction plates. Continued use will contaminate the fluid and burn up the plates.

 

Thanks for the info on keeping the OD off when towing.

 

I'll get back to you after i get back home from this camping trip on the tire and gear ratio for the truck.

 

So when you say left and right is that sitting in the truck of looking from in front of the truck? I'm attaching a picture.

 

The check valve is removed. Thanks.

 

So if I need to have the OD off while towing, does 7mpg for mileage sound about right for this truck when towing? Also will it be able to handle mountains out west. I'll get back to you later with the rear ratio and tire size.

 

Yeah. 7 doesn't seem too far off the mark. If it hasn't happened lately, plugs, wires, cap, rotor, and O2 sensors (copper plugs, brass terminal on the cap, and NTK or Denso sensors.....) Might help some. (reset PCM after changing everything.)