jmkord8703

Hey guys, this is my first post. I have started rebuilding a 1993 W250. I have found a few things on the truck that i am having a hard time idenifying. There is some kind of cooling unit mounted underneath the truck bed. Driver's side, front corner. It has an electric fan and fan shroud like a radiator. The hoses appear to go to the tranny, but the truck has a tranny cooler up front! I have asked many people about it, but no one can give me a definate answer. Please help. Joe

Crossy's son

Thats Dodge's "super cooling package". You have it , Its an auxillary transmission cooler. I believe it was about a $400 option from the factory. (we had a truck here at the house that had it, with the factory dealer sticker still)

It's a pretty rare and neat setup. There's a transmission cooler in front and rear, the one in the rear that you have has a switch in it and the fan kicks on when the fluid reaches that temp. ....But it seems as if that temperature when the fan kicks on is too high and by that time the damage is done. I think its like 250* (which you should never see being you have a cooler up front and in rear). Solution- Wire the fan to a rocker switch that you can mount under the dash and kick the fan on when doing a tow in the summer

Welcome to DTR

BC847

Don't forget the primary heat exchanger under the turbo as well.

Transmission - > Liquid-to-liquid heat exchanger under turbo - > liquid-to-air heat exchanger at front of truck (with bypass adjuncts) - > Optional liquid-to-air heat exchanger under bed - > Transmission.

jmkord8703

Thanks guys! So that was a factory option, I never new that. I will definately hard wire a switch to it. Oh, also, any good suggestions on where to get replacement interior door panels? Thanks again. Joe

Firstgenfanatic

I have the dealer installed cooler on mine. I wired the electric fan on a toggle switch in the cab. The fan works great, but I think something major is wrong in the lines or cooler............ I have climbed steep hills and passes and have reached transmission temps around 210/215/220 degrees before. I have pulled over and placed my hands under the auxilary underbed cooler (while fan is running), no warm/hot air can be felt! Hhhmmm, this really bothers me. I should be feeling heat coming off that cooler, infact the lines seem cool to me I have a bad feeling that the lines or cooler itself is plugged. Another indication is that I see no difference in operating temps whether I flip on the fan or not. Not good.......... Should I flush the lines and cooler or replace lines and install a new cooler unit? These observations just don't seem right.

apwatson50

I believe that on the inside of the frame rail, there is a thermostatic bypass valve, that when the fluid is cool, it bypasses the extra cooler and sends the fluid directly to the trans. But when the fluid gets hot it is supposed to open and send the fluid to the cooler then to the trans. My guess is that this has failed closed and always bypassing fluid.

My preference for cooler routing is:

Big trans cooler w/fan--> water/oil heat exchanger--> front cooler-->trans.

My reasoning is that when towing I want to dump as much heat from the trans before putting it into the engine cooling system. As we all know the engine cooling system is too small to begin with.

The biggest issue i've seen with this routing is that during the winter it takes longer to warm up the engine. But the alternative is worse.

BC847

Really? Since when?

apwatson50

Well it is for those of us who use power for more than a 1/4 mile at a time

unixcowboy

Does towing ~ 9K from north Tx to Lansing, Mi count ???

The temp never got past the 1st mark below hot - right where it goes just before the t-stat opens.

apwatson50

Depends, did you climb any ~5 mile ~6% grades topping out at 10k feet?

commandoNate

I put about 25k miles/year on my '92 and about half of that is towing. Bobcat, buggy, camper, work stuff, ect. I can vouch for the fact that the cooling system leaves some to be desired. It seems like if its over about 80 degrees out the motor gets a little warm. I guess if I was willing to have a 600/month truck payment I could do 75 mph up the colorado mountain passes with my camper and my buggy.

apwatson50--
you ever tow up 285 to south park/fairplay area? That hill is a beast! It overheated my buddy's low mileage 24 valve last summer on the way to Cortez.

Boatnik

I think that the cooling system is lacking because of the mods that are done. It was originally designed for 165 hp and 400 ft:lbs torque. When I am pulling anything over 12,000 pounds I need to keep an eye on the engine temperature and that is with a brand new radiator. The tranny will see about180 to 220 and the engine will see 210 at the t stat housing on a long pull. An auxiliary cooler at the tranny would help me for sure. The more heat removed from the engine the better.

Firstgenfanatic

Wow!!!! really? If so, that would explain alot. Can anyone else vouch for having one of these thermostatic bypass valves? Where are they located specifically? I will crawl under my truck soon and check........what does this critter look like? You have me wondering now............

sdstriper

The early 1st Gens with auto transmissions are more likely to have cooling system issues than the later ones.

TIMMY22

I'm surprised no one has modified the A/C condenser to become a tranny cooler. The tranny cooler up front is really small. I'll bet the A/C unit is 4 times the size. Looks like you could make some brackets and double stack 2 A/C units in there. Cut the ends 3" from the bolt and gasket block and clamp the hoses to it.
The gasoline models had a 2 in one radiator. With ports for the tranny fluid in the bottom of the radiator.