Transmission oil coolers and how cool should you go.

Apologies to everyone...especially Mark...

For some reason...memory always goes back to ATF going into the Aux cooler first...know it is from early days back in the 70's when that idea stuck when installing first external aux ATF cooler. No Internet back then and just hard copy reference material and jawing it with buddies

Terryallan wrote:

Ben. My trans cooler is AFTER the radiator, not before it. So the fluid goes straight from the cooler to the trans, and not back thru the radiator.

That is the way all the OEMs route the fluid if there is both an in tank cooler and an air to oil cooler. I studied the competition when I was an automatic transmission cooling engineer at Ford.

I don't see any reason why you would want to run the in tank cooler after the air to oil. The purpose of the transmission cooling system is to cool the ATF. The most efficient way to do that is to run the air to oil cooler after the in tank cooler.

Newer transmissions have a thermostat the bypasses the cooler until the trans reaches a preset temperature. There is no need to warm the trans fluid outside of the transmission. And the thermostat is a wax pellet type, it is not computer controlled in any way.

Any reasonably sized cooler can only be better. My primary concern is to not introduce additional fail points with the hoses etc. As much as possible I would be using steel lines and flare fittings similar to oem.

BenK wrote:
Turtle is smack on and add a few penny's of mine...

Everything has a specification and on this topic...a temperature range for *.YOUR.* truck's automatic (for the ATF spec'd out and if you change to another...then that has it's own temp range spec)

Today's TV's has dozens to over a hundred computers controlling just about EVERYTHING, which on this topic is the temperature for EVERYTHING on the TV

As long as your ATF plumbing routes it back into the main engine radiator, it will be okay to re-engineer by adding another external aux ATF cooler...again...as long as it goes BACK into the main radiator before going back to the auto tranny.

There are conditions when adding another aux ATF cooler isn't recommended and that is in extreme cold. Even routing the ATF back into the main radiator, that coolant heat management system, may NOT be able to reheat it back into the spec temp range and will be over cooled

What means is that the engine heat system has many controls that will keep the engine coolant within its own temp range spec. If your re-engineering over cools the ATF to the point that when the main radiator shuts off 99.9% of the flow into/through the main radiator...it will get over cooled by that extra external ATF cooler

But, you say N Carolina, so not that extreme cold in the winter...but it goes the other way and gets very hot some times.

The OEMs design their whole vehicle for every state in the union's conditions and 'normal' driving. TV's are at the extreme and at the highest end of their spec...if you stay within their specifications for your TV (weight, frontal area, speed, duration of WOT {duty cycle}, max incline at full spec loading, stopping at that max incline and restarting, and a big ETC) it should be okay

But if you are over any of the specification limits/ratings, then you need to re-engineer whatever to help, but it will still be over the OEM's limits/ratings

Bottom line: make sure to keep your ATF (and any other) within the OEM's spec temp range

Ben. My trans cooler is AFTER the radiator, not before it. So the fluid goes straight from the cooler to the trans, and not back thru the radiator.

Works, but not as effective in rejecting heat as would a tube/fin or stacked plate. Those tubes brazed or welded to the tranny pan won't have the surface area and the biggie for me...if it holds more fluid...it will be lower towards the ground than the OEM pan (don't off road much anymore} but that is a consideration even on pavement/driveways/curbs/etc

Key to heat rejection are these things in combo

• Surface area, more the better
• temperature differential between hot side and cold side
• CFM if air, GPH if liquid on 'both' sides (hot side and cold side)
• Laminar flow (not a good thing)

There are more attributes, but those are the main components that will dictate how well the heat rejection system works

Anyone have any experience with one of the Derale deep sump pans with the flow through tubes in it?Click

Turtle is smack on and add a few penny's of mine...

Everything has a specification and on this topic...a temperature range for *.YOUR.* truck's automatic (for the ATF spec'd out and if you change to another...then that has it's own temp range spec)

Today's TV's has dozens to over a hundred computers controlling just about EVERYTHING, which on this topic is the temperature for EVERYTHING on the TV

As long as your ATF plumbing routes it back into the main engine radiator, it will be okay to re-engineer by adding another external aux ATF cooler...again...as long as it goes BACK into the main radiator before going back to the auto tranny.

There are conditions when adding another aux ATF cooler isn't recommended and that is in extreme cold. Even routing the ATF back into the main radiator, that coolant heat management system, may NOT be able to reheat it back into the spec temp range and will be over cooled

What means is that the engine heat system has many controls that will keep the engine coolant within its own temp range spec. If your re-engineering over cools the ATF to the point that when the main radiator shuts off 99.9% of the flow into/through the main radiator...it will get over cooled by that extra external ATF cooler

But, you say N Carolina, so not that extreme cold in the winter...but it goes the other way and gets very hot some times.

The OEMs design their whole vehicle for every state in the union's conditions and 'normal' driving. TV's are at the extreme and at the highest end of their spec...if you stay within their specifications for your TV (weight, frontal area, speed, duration of WOT {duty cycle}, max incline at full spec loading, stopping at that max incline and restarting, and a big ETC) it should be okay

But if you are over any of the specification limits/ratings, then you need to re-engineer whatever to help, but it will still be over the OEM's limits/ratings

Bottom line: make sure to keep your ATF (and any other) within the OEM's spec temp range

Clicky

Isn't it true that todays transmissions and the fluids that they run are ok with higher temps? My Yukon XL Denali has the tow package, and I have seen temps above 230 (actually up to 250) when towing my boat.

I spoke with techs at two different GM dealerships, and they both told me that for short amounts of time (like climbing Ike or Vail Pass), those temps are nothing to worry about.

My F350 will barely push past 165F while towing. Add the cooler and let the vehicles on board computer worry about how cool the fluid gets. That's what my "old" '06's computer does. It will not send it to the cooler until it needs to.

Interesting response, Turtle.