Trans cooler routing/fluid thoughts.

[WickedShelby88]

Okay I know a trans cooler is a good idea, but heres the real question. I've heard it said a million times there is no such thing as having your fluid too cool. In a race car obviously I can see running the lines straight to the cooler and not having them go to the radiator at all to keep the fluid as cool as possible, but what about with a daily driver. During warm up and cold starting isn't it a good idea to have the engine coolant help warm up the transmission fluid. Just curious. Also I know some of the older trans like the one I got thats from an 86 tuna can use DEX 3 with no issues. Has anyone tried the synthetic ATF's out there at all? Is it okay to use DEX 3 even as late an 89 since there is no lock-up converter? I don't build tranny, just fix mine when its broken so I want to hear some thoughts from Chrysler guys who have had or haven't had issues deviating from +3 or now +4, not to mention cooler hose routing.

[turbovanman²]

Mini's didn't run thru the rad stock and most trannie shops bypass the rad after the trans is rebuilt so its not an issue that way. It is true you can run them too cold but I haven't found that yet but I also run a medium size cooler.

Synthetic dexron is great, I think my trans lived for a few years because of it and had no diff wear, even doing peg leg burnouts. You can run the more expensive +3 or +4 if you want but for the money, just run synthetic dexron.

[WickedShelby88]

Will do.

[ATaylorRacing]

In addition to using a big tranny cooler (not using the rad) Morroso makes an extra cooler (log style) that contains a replacable filter in it....I used that on my turbo car and it made the tranny last...all my cars are daily drivers....a full manual valve body makes the tranny run cooler due to less clutch slipage developing heat.

[WickedShelby88]

Sounds like a good idea with the full manual valve body. Went to the Moroso site and it said the cooler wasn't for street use. Hmm. I wonder why if its supposed to cool so well for racing?

[turbovanman²]

Good point, buy an inline filter, Raybesto's makes them and any tranny store should carry them, cheap insurance. Place it before the cooler so if you have a boom, its saves the cooler.

[WickedShelby88]

The line going to the cooler is the one on the top or bottom.. I always get them confused. I would think it would be on the bottom so the fluid traveling up has time to cool, but then again the coolant in the bottom of the radiator should be cooler as the hot comes from the top hose.. ahh I don't know..

[Dave]

You can overcool trans fluid. ATF needs to be ran at 175*F. Any colder then it doesn't lubricate and move properly. It's still too thick below those temps. At 195*F you actually lessen the life of your ATF by 50%. So yes, cooler is better but you can be too cool.

You should run your lines to your radiator first then to the cooler if you daily drive and don't let the fluid warm up before moving.

I need to install a temp. probe to verify if routing to the radiator first impacts the fluid's final output temp. to the case.

[WickedShelby88]

Good idea. I think I might run a trans temp gauge to see what works best. It probably wouldn't hurt to have one in the first place. I'm surprised more people aren't running them in racing app's or if they are I haven't heard one way or another. It was pretty common to see a trans temp gauge in a built rwd car.