trans cooler vs better rad?

[mtbtim]

If an engine runs too cool it will malfunction. Is there an ideal temp for the transmission to operate at?

The sweet spot for ATF is around 175 degrees. Some say running below 150 for long periods of time isn't the greatest because moisture can build up inside the transmission. Even before I added an external trans cooler, I would see temps in the 130's driving down the highway. On the city streets, I see temps a little higher. Many of these external coolers have a thermal bypass which lets the cold thicker trans fluid run straight through the cooler without going through the finned cooling channels.

On the high side, I'd start to worry when your temps start getting close to 230 because that's the breaking point where the life of your fluid starts to dramatically decrease.

Is running below 150 that detrimental to your transmission? Maybe if you never rise above that in your daily driving. This is why transmission cooler manufacturers warn against bypassing the stock radiator cooler, especially in colder climates, because it helps preheat the transmission fluid.

Running too cool is probably not so good but from my reading on the subject, the big killer of transmissions is excessive heat.

 

[96RedRunner]

The plastic tanks (leaking/breaking) are more likely to be the first problem if you take care of your fluids so they don't corrode your parts.

-Charlie

Amen to that Charlie. My 96 upper tank cracked around 340k miles 3yrs ago. I did flush n fill every two years since 2000 when I purchased it. It looked as good as your pics.

 

[mendozer]

here's another thought I had today...how long should tranny temps come up to normal?

I've noticed that lately my morning drives to work (about 20 mins) don't get my fluid above 120 or 130. Could that be a sign of an old radiator as well? Not heating in the morning.

 

[mtbtim]

here's another thought I had today...how long should tranny temps come up to normal?

I've noticed that lately my morning drives to work (about 20 mins) don't get my fluid above 120 or 130. Could that be a sign of an old radiator as well? Not heating in the morning.

No Dude. Those trans temps are perfectly normal, especially for such a short drive. The morning air is colder and will affect how quickly your transmission heats up. Now, if that 20 minute drive was straight up a mountain road, your temps would be much higher.

I work an hour away from home. With my external trans cooler ran in-series with my radiator cooler, I only hit the 140's and that when I hit the surface streets after driving on the freeway for 50 minutes. On the freeway, I'm running in the 120's to 130's the whole way.

 

[mendozer]

Oh ok so we don't worry if it doesn't hit 160-170 then? I was thinking it was ideal, like 180s for the engine

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[mtbtim]

Oh ok so we don't worry if it doesn't hit 160-170 then? I was thinking it was ideal, like 180s for the engine

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170 is ideal for the ATF but it's not a perfect system like the operating temperature of the engine where there's a cooling system with a thermostat, radiator, and fan clutch keeping the temperature within a pretty narrow operating temperature range. I think the key is to not run too cool all the time and definitely not run the super high temperature extremes either.