Auto Trans Cooler

BChad956 · Aug 27, 2008

I have a '94 3.0l a4ld automatic with 120,000 on it. it has been well maintained and seems strong. i plan on pull a small trailer with my truck (utility trailer or small boat). should i get an after market trans cooler to ensure i dont have any trans problems? the most i can see ever being behind the truck is 2000lbs. thanks!

COPPERHEAD85 · Aug 28, 2008

trans cooler is a good idea any way you look at...................jmo.

Will · Aug 29, 2008

Is there already an auxillary one on it? Older Rangers came with them.

You don't need one for that. Whatever you do, don't bypass the one built into the radiator. Even some tranny rebuildred recommend bypassing it when you upgrade but that is insanity.

Do this test--heat up a cast iron pot to 500*F in the oven. Then spread a dry dishtowel across your hands and remove the pot from the oven. Now do it with a wet dish towel. Keep some Aloe Vera handy.

Obviously air is a poor conductor. Even though the radiator is at 190*, that is a safe limit for the tranny fluid and the engine coolant is pretty much guarenteed to knock your tranny fluid back down to 190F. If you add a cooler, add it after the radiator cooler so it only has to deal with a few degrees.

AllanD · Aug 29, 2008

In MANY (most) cases the factory "in the radiator" oil-to-water
transmission cooler is plumbed into the flow path BEHIND the
Oil-to-air trans cooler.

The idea behind this is that because air is a poor conductor they want
the maximum temperature differential at the oil-to-air cooler

The OTHER (and actually more important) reason for doing it that way
is that in really cold conditions when not under heavy load it's actually
possible for the oil-to-air cooler to "over cool" the fluid (the transmission
can be harmed from being run too cool as from too hot)
so the oil-to-water cooler will actually warm the fluid back up!

Thelast reason for the oil-to-water cooler it that it works even when there is very little airflow (low speed operation) through the oil-to-air cooler.

You might find if you look that some Explorers of similar vintage ('93-94)
have a larger air-to-oil cooler than your ranger, you might want to consider simply swapping in a cooler off of one of those explorers... (junkyard part)

Be sure to flush it with solvent before installing it.

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Pete D · Sep 9, 2008

The best coolers seem to be the stacked fin kind, but they are a bitch to flush properly and some tranny shops refuse to reuse them for that reason.

Totally agree that in-radiator cooler should be last to ensure that the oil is not TOO cool in the early morning in cold climates.

Another tool highly recommended by folks who routinely pull loads (RV, ORVs, etc.) is a transmission temperature gauge that lets you know the temperature of the oil as it is coming out of the trans -- This lets driver see that lock-up is not taking place, or some other condition correctible buy slowing down, downshifting, etc.

Ranger#1 · Oct 13, 2008

Will said:
Is there already an auxillary one on it? Older Rangers came with them.

You don't need one for that. Whatever you do, don't bypass the one built into the radiator. Even some tranny rebuildred recommend bypassing it when you upgrade but that is insanity.

Do this test--heat up a cast iron pot to 500*F in the oven. Then spread a dry dishtowel across your hands and remove the pot from the oven. Now do it with a wet dish towel. Keep some Aloe Vera handy.

Obviously air is a poor conductor. Even though the radiator is at 190*, that is a safe limit for the tranny fluid and the engine coolant is pretty much guarenteed to knock your tranny fluid back down to 190F. If you add a cooler, add it after the radiator cooler so it only has to deal with a few degrees.

what if you put the aux cooler first to nock down the temp then that way the radaitor can fullly take advantadge or the semi cool fluid an further cool it as much as you can

Will · Oct 23, 2008

This is the path in the '91 Service manual.

This is from Amsoil. Tranny fluid is perfectly happy working at temperatures water would be frozen solid at. In a backhoe or loader where it works at tremendously higher pressures (thousands instead of hundreds of PSI) it isn't warmed at all and is only replaced when a line breaks and empties the system all over the ground.

Auto Trans Cooler

BChad956

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COPPERHEAD85

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Will

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