E350 Auxiliary Transmission Fluid Cooler

[smooth_pilot]

I have a 2004 E-350 with the 6.0L diesel and a four-wheel drive conversion. It has the larger OEM transmission cooler provided with the tow package. Even with the larger cooler, when towing or four-wheeling (low speed) the transmission fluid temperature often exceeds 200 degrees. I am planning to add an auxiliary fluid cooler with fan such as a B&M 70297 or Derale 13960 Hyper-Cool under the body. There is no space under the hood in this vehicle and I do not want to add extra cooling load by dumping more heat into the radiator.

From what I have read in various forums so far it seems like it would be best to tap into the fluid system between the external transmission filter and the existing cooler. To minimize the amount of heat dumped into the radiator, the auxiliary cooler would be plumbed in series with and upstream of the OEM cooler.

What do you guys think of this installation? Any comments on either of these coolers or suggestions for others? Is it worth putting a manual switch on the fan or is just relying on the thermal switch okay?

Can anyone tell me which of the lines from the external fluid filter body is the input and which is the output?

[jesilvas]

The other thing that you need to watch when running multiple coolers is fluid flow. Too little is not good.
If you want to add another cooler, fan or no, would be to put it somewhere under the vehicle, up above the frame bottom of course, towards the middle and before you get up to all the motor and stuff. Maybe outside the rail, laying flat so heat will radiate up.

[smooth_pilot]

Thanks for the observations. I was actually thinking about bumping the extension tubing up a size to minimize pressure loss if I had to position the cooler very far away from the original tube route.