I'm getting ready to put a bigger aluminum radiator in my 57 truck. My question is- I have a large trans cooler on it now that is not routed through the radiator. What are the pros and cons of running through the radiator + a trans cooler mounted in front of the radiator? I think the cooler I have been running has been fine, but the radiator on it now did not have an internal cooler for the trans either. What are your thoughts?

..isn't the "cooler" found inside a rad actually a heater for cold weather operation?
...necessary for winter operation.

I have a Morosso single pass 15" cooler and don't go through the radiator. I drove it from Carson City to Las Vegas at 60-70 MPH. The trans temp gauge never got above 190. Mostly around 180 except when zooming up a long grade. The fluid is still red. It ran 12.35 with 3.23's chnged to my tal tires and dove home,

For the best possible cooling run through the radiator first, then the aux cooler then back to the trans. Trans fluid does a fine job of getting itself warmed up all by itself and the radiator will not contribute to that much. Water pulls a lot more heat than air does, especially when the cooler is located on the "cold" part of the radiator tank as most are.

In the strictest sense, it does both. It helps bring it up to operating temp faster, and also to keep it there. That's why production cars use them - best longevity. Remember, the coolant temp at the bottom of the radiator should be low - below the temperature of the coolant thermostat.

Anyway, even though it's still relatively "hot", with a reduced delta T capability, as a liquid to liquid exchanger, it's still pretty efficient and WILL help keep the trans temperature in check if it gets high.

running an aux cooler when it's not necessary in ADDITION to looping in the radiator can keep the oil too cool, that adds friction - that's neither good for power nor longevity (and that's where the thermostatic valve comes in).

mopar cop cars often had aux coolers for both engine oil and trans, however they didn't use thermostatic controls on them, since they were run hard a lot of the time.. and no one expects them to go for 10 years anyway. (this is getting into restomod stuff, making something as good as it can possibly be)

If you only drive the car here and there, once in a while.. then a lot of this argument goes out the window and becomes "who cares." Your mileage may vary

Alright, to fill in some of the missing links. This setup is in my 57 Dodge truck. I am running a 512 stroker, 3500 converter going back to a 4:10 geared rear. I don't know what the truck weighs, I'm guessing at least 3600 lbs. Like I said in my original question. I am running a large external cooler now and you can easily hold your hand on it after running down the road at 3000 rpm for extended trips. So, it seems to be cooling pretty good. No, I don't have a trans temp gauge, probably should. My radiator on it now doesn't have provision for a cooler, this is why I haven'y used the radiator before. My new Champion radiator will have provisions for a trans cooler. I was just wondering about using it and the external cooler for maximum effect.

that's a pretty beefy setup. Big engine, big load on the trans, a decent converter. If I were you, I'd do a standard rig - plum to radiator, then radiator to air cooler, then back to trans. I think you probably have enough heat in that trans to warrant a setup like that without needing to worry about a thermostat (although I'd still do it, personally)

the converter and shifting is what generates the majority of trans heat. going down the road at part throttle in final drive, over stall speed, there's not nearly as much slipping going on i.e. heat generation. it's the flash temperatures that hurt, and that basic test isn't going to show you that

definitely would put in a temp gauge

I mimicked the factory HD cooling package used in cop cars on my Diplomat. Which means both coolers for the trans. I figure the factory knew more about it that just about anyone else.

While I generally agree that the factory engineers knew best, i.e. using the cooler in the rad, plumbed in with aux. cooler. . . .I can say from history (like 100,000 miles plus !!!), I have used just a aux cooler (no rad mounted unit) on my 1974 Duster360, factory 727, factory stall (approx. 2600rpm)with 2.45 gears, with no issues. I usually drive long distances for car show trips. And then just as daily driver around town . . . tranny fluid looks like new, and tranny shifts fine.

I would say you are ok to go with the set up you already have. . . . Somewhere in all the time and miles, I recall hearing that for every 10 Deg F. you drop tranny fluid temp, you DOUBLE the life of your tranny (is that true ???) . . .

Just my two cents . . .

Cheers

Mark