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Hello, after a moderate trail last weekend I noticed the transmission of my '91 XJ was fairly hot. I'm thinking of installing an external transmission cooler instead of the one in the radiator tank. Has anyone done this and has it been as sucessful as you hoped in keeping the trans temp down?
I put one in my XJ cause I'm running 36" tires with 4.10s(5.38s are on the way). Anyway just went to the wrecker and found one from a van. Modded up some brackets and picked up some adapters for the lines. I think I spent $20 in total. You can buy kits that have all the pieces you need and save some time.
BTW you should put it inline with the cooler in the rad, don't eliminate completly. Especially if you live in a cold climate.
There is another thread titled "Transmission cooler, ditch stock cooler? " dealing with this question that I didn't find by searching last night. Since I live in snow country I will keep the stock cooler/warmer in the radiator and look for a good place to stick an aux cooler.
The idea of a trans cooler is to keep the temps down, preferably under 200 degrees.
Kinda defeats the purpose to run the ATF through a radiator that's 210 degrees first doesn't it?
Bipass the radiator cooler.
Aftermarket coolers aren't that expensive but if you have a pick and pull wrecking yard nearby you can find a stock cooler from some vehicles for really really cheap. I bought a B&M stacked plate tranny cooler for my ZJ and it came to about $50 with all hardware. A couple weeks later I found a stacked plate cooler that came stock on a ford explorer at a wrecking yard for $5...looked pretty much identical to the B&M unit.
I'd also suggest putting it inline with the stock rad cooler if you live in any climate that gets cold.
Also, I could be wrong but most of the setups I've seen have the stock (inside radiator) tranny cooler on the "cool" side of the radiator which is hopefully much below 210 degrees. If the temp at the cool end of your rad is 210 the highest coolant temp in the engine is probably closer to 245 degrees and you've got problems.
ATF doesn't need to "warm up" on cold mornings. Even if it did, the trans will warm up way before the thermostat will allow any warm water in the radiator. So now you're running the ATF through a cold radiator.
You have a lose, lose situation. The radiator will help keep the ATF cold when it's already cold and will heat it up when warmed up.
Bender said:
Also, I could be wrong but most of the setups I've seen have the stock (inside radiator) tranny cooler on the "cool" side of the radiator which is hopefully much below 210 degrees. If the temp at the cool end of your rad is 210 the highest coolant temp in the engine is probably closer to 245 degrees and you've got problems.
I'm open to discussion on this but if what you are saying is true then what is the purpose of this style heat exchanger that seems to come on every automatic vehicle regardless of manufacturer?
I'm open to discussion on this but if what you are saying is true then what is the purpose of this style heat exchanger that seems to come on every automatic vehicle regardless of manufacturer?
You do need some kind of trans cooler and the radiator style is better than nothing but it will keep the trans temp at whatever the water temp is.
I try to keep my trans temp under 200 degrees.
I can also say this firsthand because I orig ran mine as you suggested before changing it.
It now rarely goes past 200 and used to regularly get up to 230. (which is why I tried the bipass tip)
I do have a good size cooler though. I'd recommend the largest volume one you can fit. They're all pretty cheap.
I'm open to discussion on this but if what you are saying is true then what is the purpose of this style heat exchanger that seems to come on every automatic vehicle regardless of manufacturer?
here's my install write-up on a B&M cooler. I bypassed the radiator when I installed it, but I didn't go into that part in the write-up. So far so good, but I haven't had a chance to get it back offroad yet since doing the cooler and rad bypass.
Factory external coolers are plumbed in-line with the standard in-radiator cooler, they don't bypass it. That's the way I would do it if I were adding one.
