Keeping the Automatic Cool

[GasSavers_Pete]

Car makers fit the trans cooler in the radiator to moderate the temps of both units.

The engine coolant helps get the trans up to operating temp more quickly then it would alone and it also helps limit the upper temps by allowing the trans heat to be taken up by the same radiator coolant.

Normally a thermostat is fitted to protect the trans cooler from excess pressures from cold fluid as much as regulate the temp of the fluid.

Nearly all cars run a ( relatively speaking ) lower pressure area in the wheel wells so fitting a duct to allow air to transit from the higher pressure area ahead of the rad to the lower pressure area in the wheel well will not need a fan.
You may want to consider some sort of flap / louvre arrangement to stop road debris coming into the duct.

Pete.

[kamesama980]

-A PC fan will be dead in days because it is far from weatherproof. oyea, and 15 cfm it'll move is worthless above 1 mph.

-mount the trans cooler before and in line with the factory in-radiator cooler only IF NEEDED. Keep in mind your transmission is fine unless you're doing lots of towing or up steep hills...high load conditions like that and the transmission fluid does need to be around operating coolant temperatures to be at it's best: it's engineered that way.

-if your radiator cooler is set up like mine and runs the trans fluid through a tube in the radiator (helps heat up and keep from overheating) it will be moderated by the coolant. unless your coolant starts overheating massively, the trans fluid won't overheat either. that is unless as stated above, you do lots of up-hill towing or drag racing.

-in-line pump: DON'T. during normal operation (any time not in park) the rotation of the torque converter connected to the engine spins the pump in the transmission. adding another pump in-line will do one of two things: block flow (bad) or cavitate if it's powerful enough. (less bad but wasting the power to spin it) and you'll have a hell of a time matching it to the pump in the transmission (changes with engine rpm. same problem as electric superchargers)

[mjo]

Originally Posted by kamesama980

unless your coolant starts overheating massively, the trans fluid won't overheat either.

In the summertime, the coolant in some cars will routinely peak above 210 degrees in stop & go city driving. The engine usually tolerates this but it will damage an A/T to some degree.

It also depends on where the transmission fluid heat exchanger is placed in the engine cooling circuit.

[mjo]

Originally Posted by Pete

Normally a thermostat is fitted to protect the trans cooler from excess pressures from cold fluid as much as regulate the temp of the fluid.

I didn't know that some cars have thermostats to regulate flow to the trans cooler. Can you give some examples of cars that contain such thermostats? I have a Saturn SL1 and SL2. Both have automatic transmissions and neither come stock with transmission thermostats.


Keeping the engine cool by heating up the transmission is not a benefit to having a transmission fluid/ engine coolant heat exchanger. Engine temperatures vary wildly with speed/throttle position/ ambient temperature. A heat exchanger passing on these wild temperatures to the transmission will cause the transmission fluid to have varying viscosity. This doesn't help the ECU any because it must relearn how fast it should activate the solenoids. When I put an external transmission radiator on my SL2 it caused the transmission shifts to be much more consistant and firm. Before the transmission would tend to be too fast and slam when the engine was hot and too slow when the engine was cold. IMO, reducing the ECU relearning is another factor that should help reduce the transmission wear.

Originally Posted by Pete

You may want to consider some sort of flap / louvre arrangement to stop road debris coming into the duct.

When I installed the external transmission cooler I wrapped the cooler in aluminum screen. The stones and bugs bounce right off of this screen.

[mjo]

Originally Posted by Pete

Normally a thermostat is fitted to protect the trans cooler from excess pressures from cold fluid as much as regulate the temp of the fluid.

I didn't know that some cars have thermostats to regulate flow to the trans cooler. Can you give some examples of cars that contain such thermostats? I have a Saturn SL1 and SL2. Both have automatic transmissions and neither come stock with transmission thermostats.


Keeping the engine cool by heating up the transmission is not a benefit to having a transmission fluid/ engine coolant heat exchanger. Engine temperatures vary wildly with speed/throttle position/ ambient temperature. A heat exchanger passing on these wild temperatures to the transmission will cause the transmission fluid to have varying viscosity. This doesn't help the ECU any because it must relearn how fast it should activate the solenoids. When I put an external transmission radiator on my SL2 it caused the transmission shifts to be much more consistant and firm. Before the transmission would tend to be too fast and slam when the engine was hot and too slow when the engine was cold. IMO, reducing the ECU relearning is another factor that should help reduce the transmission wear.

Originally Posted by Pete

You may want to consider some sort of flap / louvre arrangement to stop road debris coming into the duct.

When I installed the external transmission cooler I wrapped the cooler in aluminum screen. The stones and bugs bounce right off of this screen.

[scdave]

wouldnt a shroud around the trans cooler be helpful to make the cooler more efficient?like sheetmetal pieces to farce more air into the cooler. also, i always thought that the cooler the trans oil,the better.

[kamesama980]

the engine temperature does NOT vary much or quickly with loading. the radiator temps certainly don't. put an aftermarket gauge in the thermostat housing in your engine and after getting the engine up to temp, cruise at a constant speed with a couple peeps in the car with you...then floor it for 15 seconds and watch the temp gauge. it'll slowly go up MAYBE a few degrees... Besides, you guys barely touch the gas in the first place. I've got slightly higher performance parts than a saturn and I drive a lot harder than you guys and my cars fine. hell drifting didn't bother my engine...or trans one bit (WOT or near enough for 5 minutes at a time)

Most trans coolers are placed on the cooler end of the transmission. in my cressida, the radiator flows from top to bottom and the tranny exchanger is in the lower tank....well below operating temps.

As for the engine being heated by the transmission....the amount of heat the transmission generates is insignificant compared to the engine heat and far overshadowed by the size of the radiator and volume of coolant.

[GasSavers_Pete]

Originally Posted by mjo

Can you give some examples of cars that contain such thermostats?

Sorry for the delay ; I lost track of the thread !

Some of the Land Rover / Range Rover vehicles had them but they may have been part of an options kit for low temperature environments.

Many years ago we owned an a Land Rover which was ex Snowy Mountains hydro scheme and it had one fitted.

I recall a friend having trouble getting a suitable temperature range replacement for one fitted to his Land Rover Discovery and I think there were some Jaguar models which had them as well.

Pete.