Trans cooler---size, seasonal use, etc

I wouldn't worry about using a larger cooler and install the largest one you can fit under the grill. Heat is an automatic transmission's worst enemy. Years back before transmission coolers became fashionable; I removed the condensing coil from a window AC and installed it. The transmission fluid was returned to the unit at almost ambient temperature. There were no ill effects even during the winter months. Also, if your cooler is big enough just bypass the radiator all together.

Rita

Exactly what Rita said. I've done this in my wife's ZJ, my XJ, and my S-10 with no problems at all-- totally bypassed the in-rad cooler.

As a bonus, the engine runs cooler, too!

Thanks Rita and nyb... I'm also pitting in a TransPro 4-row radiator, so cooling shouldn't be a problem anymore! :-)

Here are a few FAQ's from the Hayden web site that might help you.

+++++++++++++++++++++++++++++++++++++++ TRANSMISSION OIL COOLERS Q. The trans cooler in the radiator is leaking and is expensive to repair. Can I use a Hayden transmission cooler to eliminate it? A. Yes. Always choose one of the larger Hayden coolers when eliminating the radiator cooler to compensate for the loss of cooling from the radiator. In most installations we recommend use of the radiator tank cooler to provide maximum cooling and to comply with most manufacturers warranties.

Q. Should the cooler be installed before or after the radiator? A. Hayden recommends installing the auxiliary cooler after the radiator to return the coolest fluid directly to the transmission. Installing the cooler before the radiator will still provide additional cooling and may be necessary in some difficult access applications.

Q. Can you over cool the transmission fluid? A. Transmissions are not highly sensitive to cool operating temperatures. However, in sub-zero (20-30° F) weather conditions transmission fluid can actually gel up in an external cooler and cease to flow, causing damage. Use of the radiator cooler actually helps warm the fluid under these conditions. It is critical in extreme cold conditions to use the original equipment cooler in series with the auxiliary cooler and allow the vehicle to warm up before driving.

+++++++++++++++++++++++++++++++++++++++

If you live in a climate that has cold winters I wouldn't bypass the cooler in the radiator. Remember the wind chill factor when driving 70 MPH down the road.

Brian

wind chill only effects things that lose moisture (i.e. living things or evaporative cooling systems). the cooler won't know the difference between an 8 or 800MPH wind.

-Bret

Well, I opened my old text book on thermodynamics and you are correct. Wind speed won't effect a given temperature of an inanimate object.

Thanks for the correction.

Brian

If you live in a climate with cold temperatures, chances are you're going to have fluid heaters and additive packages appropriate to the climate in the first place.

Even an OEM tranny setup with the fluid in the cooler in the tank will gel up if it's left overnight.