I've been wondering this for some time. A few guys swear to me that an external cooler will run much cooler without the stock one. Yet I hear the exact same argument reversed cuz someone claims it will run cooler with the stock one cooling the fluid first, then the external.

I got my beliefs, you got yours, but who has proof; who has used a gauge both ways?

I searched and skimmed through a few threads, lots of claims, but not much proof. I'll make a poll....

 

im interested as well. i have heard both sides of the story. someone on here said that some companies wont warranty a transmission that has the cooler inline with the stock one. so idk what to believe anymore lol. i was planning on running mine with the stock one until i read this now im second guessing this.

 

Warranties are a legal matter, exclusions are about
stuff goes wrong, not what's normal.

I have my aux cooler first, then into the radiator heat
exchanger. But mounting the aux cooler in the radiator
air path "robs Peter to pay Paul" in a sense. Best would
be a thermostatic, has-its-own-fans cooler that you put
somewhere that the radiator doesn't see (or throw heat
onto, or vice versa). But those are pretty expensive.

 

I say with coolant and trans fluid running so close together in the stock radiator that leads me to believe a few things. 1. Trans fluid will warm up quicker bc coolant temps warm up fast. 2. Trans temp will ultimately try and follow coolant temps, for better or for worse. Although most of the time my trans doesnt reach the coolant temps, it stays below it. Im running both coolers inline.

 

Here are my thoughts on this. The transmissions on GM HD2500 and 3500 trucks generate a lot of heat because of their intended use. Not one of them has a cooler in the radiator. They all run an external cooler only. If it would work better running through both coolers, most likely GM would have done it that way. I'll bet if you look at Ford and Dodge heavy duty trucks and any motor home, you won't find a one with a radiator cooler and an external cooler.

 

we arent driving HD trucks that pull trailers across states though.

 

True , however trannys with a stall generate massive amounts of heat. That's why the Ultrabells leave the bottom 1/2 of the converter uncovered, just to dissipate heat. IMO, no radiator cooler.

 

my perofmrabuilt trans came with specific instructions to bypass the stock cooler or the warranty could be voided...that i would assume is for good reason since they are trans builders...

 

No you're not, but why would you want to heat the tranny fluid? That's basically all the radiator cooler is doing if you also have an aftermarket cooler.

 

i dont know im not a transmission builder. Why dont one of the sponsers chime in and lets get some expert opinion. My tranny runs 140 on cool days even when the motor is 190. Obviously fluid flows differently from cold to hot. Maybe the trans engineers designed the trannies to work good with luke warm and up fluid temp?? who the hell knows.

 

I could see you being right if we're talking about a stock car that doesn't see high trans temps....as soon as your change something that will cause it to run hotter you'll need to be able to dissapate that heat quicker...a stand alone unit like in the HD trucks is a prime example...when a trans is put under a heavy load (drag racing) they need to be kept cool...I don't see how running already hot tranny fluid in a cooler with hot anti-freeze is going to benefit any performance application...I voted external cooler cause every setup I throw together I always recomend externals...and always see the lowest temps that way....

-Dave