transmission cooler (Just noticed today)

[LEggers]

I have a H/D transmission cooler mounted under my bed in back. Today after a trip pulling a 20' car trailer I noticed it came on. No problem but I never had heard it come on before.

I also noticed it cam on when I was backing the trailer up. Just for the heck of it and yes I know it was doing its job by coming on I check the transmission fluid.

Nice and clean and up to snuff.

I figured it was normal.

Loaded up and hit the freeway. When we get to our drop off location I sat at idle for about 5 minutes so we could move some cars around to back the trailer in were it needed to go.

The fan never came on while we were sitting there. As soon as I start backing the trailer up the fan came on again... Hmmm



My question after all of that is why would it come on more when in reverse and not in forward or do you think its just that I do not here it while in forward motion?



THanks for your input

Lance Seattle, WA. :-laf

 

[DPetrey]

There could be a gremlin in the wiring or, it can be that all the air passing over the cooler when you are moving forward keeps it cool enough may want to check the wiring and the thermestatic switch and the ground which i think is under the bed exposed to the weather.

 

[Philip]

This is normal. An auto trans in reverse makes more heat than in forward gear.

 

[Greenleaf]

I have found that to be true az well



GL

 

[paccool]

Mine comes on a lot faster when backing the travel trailer up a slope than at any other time. When pulling a long grade in hot weather it will come on if I don't back out of the throttle a little or shift out of overdrive. The transmission heats up a lot faster in OD than out when pulling a load up a grade. Since I put in the new converter, I hardly ever have the cooler kick on so I am guessing I was getting more "slip" with the old converter than the new one. I also went to synthetic fluid (Amsoil) which seemed to help keep temps down as well. transmission temps are normally in the 160-180 range when towing unless headed up a grade and pulling hard when it will sometimes go just a little above 200 degrees.

 

[Philip]

I'll explain a little better. A auto trans in forward uses hyd pressure in the 90 to 160 PSI range for all forward gears. The trans is setup for the least amount of internal drag in forward gears.



In reverse a Dodge auto uses anywhere from 190 to 250 PSI to make the vehicle move in reverse. When you have this high of pressure and it is not all being used. It will start to heat up fast and cause damage if you do a prolonged backing session. So make your reverse times as short as possible all the time.

 

[tugboatphil]

Lance,



Since our trucks are all the same age (more or less), I wanted to share my experience from this past summer. I knew the cooler was there, but never paid it much attention. As I was driving home from a road trip, I noticed the power seemed to be dropping (flat road. ) I got out to check things out and noticed the film of transmission fluid on the tailgate.



The lines were running between the fuel tank and the frame. In a very hard rain that day, I had run off the edge of the road and hit a huge pothole. It's my guess that this pinched one of the lines. The leak was small enough that it took that long for the level dropping to be noticeable.



I crawled under to look and without any replacement hose (oh yeah, it was also getting dark) I realized that bypassing the cooler was the only way I was getting home. So I took one line off and bent the other around in a loop.



Well, being as lazy as I am, I never got my replacement hose. I also never tied the hoses up very well either. Two trips later, I was going down a residential street and thought I heard a hissing sound. I turned down the radio and sure enough, either I had picked up a very mad snake or something was leaking. I looked underneath and the hose had dropped to the road, and a small hole had worn through.



So I pulled the right side up onto the curb and had to re-patch the bypass (maybe I should try heart surgery for a living?) In each instance, I swore that I would get new hose for the entire system..... I haven't yet. But if you have this cooler, take a good look at how the hoses are rigged. Let my stupidity be your motivation!!