Ok, I'm sure this is a dumb question but I did a quick search and didn't find the answer. Is the cooler in the radiator necessary for a c6 tranny or can I just use a external cooler and be ok?

 

You can use an external cooler and bypass the radiator cooler and be fine.

 

You can bypass it, but you lose a lot of cooling capacity, especially at low speeds.

 

Both is better, no?
First the external, then the radiator.
Helps with coolant temps.

 

Both are better. First the radiator, then the external.

 

What size cooler should be used? The bigger the better?

 

Size of the cooler all depends. You do not normally want the biggest you can find, you can over cool the tranny, especially in cold climates.

My 94 F250 E4OD with factory coolers tows my 8,000# trailer just fine. I don't think I have ever seen more than 230 degrees and that was after a long hot tow and after I pulled off the freeway and was backing up my driveway, ie worst case conditions for cooling.

Normally I rarely saw anything over 200 on hot days and sometimes it takes an hour or two if it is freezing outside. Without a trailer it could take several hours to crack above 150, at least when I lived in Oregon.

Some more expensive coolers even have a thermostat to prevent over cooling.

Pick a cooler that is at least rated for the heaviest thing you will tow. But don't go for "the big one" unless you really need it.

Just my opinion,

Jim Henderson

 

I was told that autos run best and last longer if they operate at 175* but that most newer engines run at 195* so I put an external cooler that is rated at 12,000 lbs with it's own fan and thermostat it does the job and only runs when the trany gets above 175*.