I'm installing a rebuilt E4OD with billet converter into my 1997 F-250 7.3 and I purchased a 6.0 ( Mishimoto ) trans cooler to pair with it. Now I understand this cooler may be overkill for my setup, so that's why I plan to install an external thermostat to regulate the trans fluid temps.
I'm looking at thermostats that are available in stabilized temps of 145, 165, 185, and 215F degrees. I'm leaning toward the 185F, but can anyone tell me what fluid temperature range the E4OD was designed to operate? ( Mark K? )

And let me say that removing this transmission at home on the ground, alone, was the BIGGEST PAIN IN THE *** I have ever encountered working on anything. It surely seems the 7.3 PS was NEVER supposed to live in the OBS chassis ( one that was designed in the 1970's ). I decided not to cut up my downpipe in the truck, that I could pull it out once the trans was out - WRONG! It's still hanging there!!! -I'll drop it when I change my up-pipes and install my coated 3" DP.....

 

A good syn oil I've read up to 250*° but I believe 215*° would be about right. Years ago I put a true-cool trans cooler in with the thermostat and had over heating problems. I finally threw it out. As far as the down pipe, use a sawzall to cut it in half. Don't use a torch, one guy burned his truck up doing that!

 

The 185F thermostat is the best choice. That will keep the trans temp around 160-170F, which is ideal.

 

 

I should have clarified, 215° when I'm towing that 5th wheel in my signature.