archer2

I had done this but I used a condenser from a Daytona. I tapped pipe threads in the block and put in hose barbs and ran that as my only cooler for over 80k miles until I pulled out the 727 and put in the 618. I had installed it under the bed, I never did have a temp gauge back then and I did very little towing, maybe a car and trailer on rare occasion. The trans still worked good and didn't slip when I pulled it.

DBF

It's a "H" shaped thing close to the SuperDuty cooler. Both the supply and return lines to/from the cooler run thru the legs of the H; the middle of the H is the bypass.

DBF

whosdunit

My 91 D350 has this cooler under the cab ,no lines fromthe radi. thanks for the info. mine stk. with 167k .
thanks to DBF
from whosdunit.

Crossy's son

Lots of underbed cooler discussion in here.

I have someone local that has a 92 Dually W350 with the underbed cooler, he tows. It has a BD torque converter and thats it, upgraded years ago. Says he likes it.

He has an autometer gauge in the pan and says he's seen 200* and the fan didn't kick on under the bed, and he feels like the fluid temp. wouldnt be 200* if the cooler was being used

what temp. does the fan kick on/valve open ??? does this frame mounted valve kick on before the fan or both at the same time?

I think he's just gonna figure a way to wire the valve and the fan to a toggle switch rather than having all the automatic temperature stuff.

But is there a way to replace a temperature switch with a lower temperature switch? Like lets say a 200* switch or something.

thanks

Firstgenfanatic

So does this "H" shaped fitting sieze up or have issues with 1st gen owners? What if I pull it out and install an open "H" fitting? I haven't tested it yet, but it sounds like a likely part that is causing me heat issues.

wollfgang

Mine works as it's supposed to fan comes on with heavy towing wideopen up a steep hill low gear at about 230 degrees and I know for sure it goes through the cooler as cooler gets hot and I broke a hose once right at the cooler and left alot of fluid on the road.(I believe about 5-6 gal, I first went to a part store and was told not over 3 gal in my system went back with 3 and went back a second time for 3 more)

DBF

The fitting has no moving parts. It works on viscosity of the fluid. When the fluid in the cooler is thick (cold), it's easier for the fluid to enter one leg of the "H", cross over to the other side, and return out the other side of the "H" to the engine and heat exchanger for more warming. When warmed up, the "H"'s crossover (quite small) is more restrictive than the cooler, so fluid goes through the cooler.

I'd like to remind people that the heat exchanger on the passenger side of the block works two ways. If the trans fluid is hotter than the engine coolant, heat is passed to the coolant to be returned to the air by the radiator. If the engine coolant is hotter than the trans fluid, it passes heat to the trans fluid - mostly needed in cold climates to get the trans up to the temperature it likes.

So, if you're towing uphill and engine temperature rises (say, due to a partly-plugged radiator), the excess temps will heat up the trans fluid. So you have to make sure the radiator fan is pulling air as well as the cooler fan and that the radiator is efficient.

The gage in the pan is a good start, but not enough IMHO. The fluid in the pan is going to be sucked into the transmission. If it's hot, it will only get hotter as it does its work inside the trans. I have another gage on the output of the transmission and watch that gage closely to see if I want to slow down or manually switch on the cooler, or both. I try to keep the outlet temp at or below 200* - if it goes higher for a long period, I make sure to change out the fluid earlier than normal (or very soon). I watch the pan gage as well to see what it's doing.

Regards, DBF

Jim Lane

I also have this Super Duty Transmission Oil Cooler on my truck and I do not have this bypass anywhere in the circuit.

I remember at one time reading a Service Bulletin on how to install this bypass into the lines because of problems of cold weather drivability, simply the thicker fluid will bypass the fluid resistance created by the passes through the chilled fin and plates of the cooler.



This is also another version of bypass that was installed on later years.

http://dodgeram.info/tsb/1995/21-03-95.htm

I have a full description of the Super Duty Transmission Oil Cooler here.

https://www.dieseltruckresource.com/...r-t264993.html

Jim