I just came back from smoky mountain. As always the truck was running strong.
I replaced the Oem tranny cooler with the aftermarket as a preventive for the coolant leak
my worry is the tranny temp didn't went over 125 even after hours driving hard on mountains.
even a little lower after many miles on highway

Is this temp safe and good for the transmission
btw here are a couple pics

 

I have been to NC mountains many times carrying 3 people, 1 large dog and large roof box. During mountain driving temp was like little above middle of the gauge assuming 200F-210F? Manual says "The normal operating range is from 100°F (38°C) to about 265°F (130°C). "

 

That was the avg temp before replacing the cooler.
This one works much colder than oem

I feel better with the gauge under 200 but im not sure if 125 is way too low after a day going up and down hills

 

I don't know how it compares since I have a 6 speed transmission, but on flat roads at 70F, i'm getting 124F - 126F around 55mph.

I'd think, stock, you'd get much higher w/ a 4 speed.

How large is the cooler? Maybe it's just extremely efficient in comparison to the oem cooler? Air temp up there? The cooler will be far more efficient at the temps drop. How're the temps back in FL?
As long as you're within acceptable temps, I don't see a problem.

 

Hi killer

is a TRU-COOL MAX LPD47391 .
The avg temp in Tennessee was around 65 .
FL around 85
however not matter outside temp the fluid temp stay at 125 or even lower while driving hyw @70 mph

I hope it is something that will not damage the transm at short time but I guess efficiency could be reduced with this low temp on the long run .
let see how well it perform in a month when temp rinse to 90

 

I drive about 25 miles.
The last 5 were at 70mph.
Ambient temp was 82F.
Max temp hit 147F at that time.
Otherwise, temps sat around 130ish.

Leaving (vehicle sat 30 min in the sun), temps rose to 170ish?
Never exceeded that & dropped as I drove.

 

I did the same to my deuce, you can look it up on the web about tranny temps. A lot to say about it. Basically what it says is if you keep your fluid temp below 175 your fluid will stay good. Above that it starts to go bad and lessens the life of your fluid, which in turn wears your tranny out. By the way in 100 degree weather mine never rose above 140 degrees.