4r70w Trans cooler for offroad | Ford Explorer Forums - Serious Explorations

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4r70w Trans cooler for offroad


New Member
January 2, 2019
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City, State
San Jose, Ca
Year, Model & Trim Level
99 Exploer XLT 5.0
I'm building up a 98 explorer 5.0 for a rock crawl trailer queen. I'm new to wheeling with an auto and want to make sure I don't run into heat issues or over cool the trans. I'm still building but need to relocate the stock cooler to fit the winch, so If I need to add one now would be the time. I have already added a trans temp gauge.

Superduty D60 front/Sterling Rear w/5.38
Atlas 4.3
39.5 TSL

I've been reading the old threads and there seems to be conflicting info. I've read the 5R55 needs more cooling but the 4r70w with the factory cooler does not. If it should have more cooling is it better to add a 2nd stock cooler, or to run a larger single cooler>

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You always need more cooling on a stock system on a slow speed rig. The 5r needs to be babied way more than the 4r70w, just because it is a wimpy trans from the factory. Add a larger, or second cooler where ever it’s convenient.

a single, larger unit would be the least likely to have an issue vs multiple coolers/connections.

remove the factory radiator cooler from the system and run two factory style plate and fin coolers in series tucked up tight to the cooling stack and your 4r70w will be happy. The tiny fluid to fluid cooler inside the radiator actually works more as a pre heater then a cooler due to its size....so instead of running it and risking mixing water with Atf when it fails, just remove it from the system

There have been many very large OEM ATF coolers on bigger trucks. Those would be better and often cheaper than any aftermarket cooler.

These trucks have great cooling capacity, which helps a ton when adding larger front bumpers and blocking some of the airflow. So if possible, place the cooler up higher into the grille area, noting the AC will be affected some.

The best fitting cooler seems to be a very long one from an early 2000's Super Duty truck, they are short enough to go under the center radiator support section, and fit side to side well. There are a couple of threads here showing that one, Traveler I think was the first to put one in.

BTW, it's hard to over cool an automatic, I've never heard of anyone actually achieving that.

Auto trans in a rock crawler will always need more cooling, not less. I have a tube and fin cooler, and a large plate cooler with a electric pusher fan on it and mine still runs hot when going slow. I have a GM 700R4 trans but same issue. Bypass the radiator as 410 mentioned for three reasons; 1) it acts like a pre-heater and does nothing to cool the transmission, 2) in my case it seemed like the engine and trans were heating each other up and overall temps went down after I bypassed, 3) It keeps them as separate systems in case one fails while on the trail.

Please start a build thread here
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