I'm getting ready to install a big,new trans cooler and am wondering how to connect the hoses. My 2500 has the in-radiator cooler plus a single loop cooler between the radiator and A/C condenser. It is routed from transmission, to the loop cooler, into the upper port of the radiator cooler, then from the lower port back to the transmission.

My first instinct is to install the new cooler between the lower port of the radiator cooler (which already has a barbedfitting and rubber hose with hose clamp)and the transmission, which "should" make it last in line. This makes sense becausecommon sense saysthe fluid in the radiator cooler should flow from top to bottom. But if that's the case, why would the OEM engineers have the fluid go through the loop cooler then into the radiator (where it may actually get re-heated), then back to the transmission? IF that's the case, I should install the new cooler between the loop cooler and transmission. That doesn't seem right for some reason, plus the OEM hoses on this section are steel and not so easy to cut and splice.

ANd I already tried to determine which one was the return by checking temperatures, but how can one tell the difference between "Wow, that's really hot!" and "Holy crap, that's hot!"?

Any suggestions as to which way to install the hoses? I want the new cooler last in line obviously, but can't determine which hose is the feed and which is the return.

Thanks in advance!

 

Personally, if I was in your shoes, I would go from the trans, to the stock radiator cooler, then to your new cooler, and back to the trans. Get rid of that other cooler completly.

On my '99 1500, the return line is the one coming out of the top of the radiator. So mine goes from the trans, into the bottom of the radiator, out the top of the radiator, into my aux trans cooler, out my aux trans cooler, and back to the trans. I was told the reason they have the fluid flow through the radiator from bottom to top is in case you get an air bubble, it can push it up rather then having to force it down through the cooler. Not sure if this is a valid reason or not, but that is definetly the direction it flows on my truck.

 

It's all in the burn pattern that they leave when you grab it with your hand... sorry couldnt resist.

I'd ditch the radiator cooler all together and just go with the external one... my '05 only has an external cooler, my '00 I ditched the rad cooler and went straight to the exteral one.

 

I kept my radiator cooler because ambient temps gets down to the single digits and below 0 in the winter time here where I live. The radiator helps to get my trans fluid up to a reasonable operating temp quicker. My trans only runs between 120 and 140 degrees most of the winter, even after warmed up. I've considered bypassing the radiator the rest of the year though, but have not got around to trying it to see if it made any difference. The way I see it, in the summer time, temps are already going to be higher (like up in the normal operating range), so going through the radiator first is probably not going to warm it up any (since that's the same temp range my coolant is running), and then it will go through my aux cooler anyway. So I don't see how it would be much different then if I just bypassed the radiator all together.

I think the ideal thing for me to do might be to run just my stock radiator cooler in the winter time (when not towing or hauling loads), and run just my aux cooler in the summer time. Probably keep trans temps closer to operating temp in the winter time that way, and also keep things coolest in the summer time.

 

What is the optimal temperature range for the transmission to operate?

 

180-195 is normal operating range according to the service manual.

 

good to know i run 200 - 210 in this summer heat with the 195 tstat. so im in the range..

 

I run about 180 in the summer heat, and about 165-170 the rest of the time. Run less then 150 most of the winter time.

My t-stat is 180 by the way.

 

my routing is hot line into bottom of rad. and out the top. then into top of external cooler and out the bottom, then back to trans. hot line is the one with the little check valve thing. to prove it, disconnect the lines, stick them in a bucket and crank the truck. here's some pics.
https://dodgeforum.com/m_717634/tm.htm

 

Perfect. That's exactly what I needed. Thanks!