tranny cooler design questions

Igoverts thread reminded me of something I have to figure out on my bonneville project, and I'll try to keep it short, but I'll fail :)

Ages ago when I was in the meat of the customization, (http://www.curtisandkim.com/bonneville.htm for those of you who don't know) I made a choice on the tranny cooler. The radiator I have is an aftermarket aluminum radiator from Griffin that does not have the auto tranny heat exchanger built in. The plan was pretty elaborate. I ran the cooling lines to an inline double filter, then a large 10x18" 4-pass cooling unit with its own 10" fan on a thermostat. I had the thermostat set to come on at about 190.

I was told that my transmission would never get hot enough with that much cooling, but then I was also told that was BS. I had a guy tell me to drive it around the block and then lay my hand on the TC and see if its too cold. Well, I did, and it was certainly warm.

What happens to transmissions if they're run too cold? am I cooling it too much? I have a tranny temp gauge to install; what temps are acceptable on the low end?

I've heard that if the tranny fluid doesn't get hot enough, it will not lubricate as well as it will when its warm. I would think a good temperature range for the tranny would be between 160 and 180 but this is just a guess as most tranny coolers are in the radiator and the coolant temp is usually around 180. Is the cooler mounted infront of or behind the radiator? I'll do some more research and get you a better explanation as automatic transmissions have always left me somewhat mystified.

The cooler is in front of the radiator. Thanks for the reply. I've been researching it for so many years and I keep running into the old guys who regurgitate stuff that has been misconceived for 40 years.

Thanks :)

I just found this website that gives a basic crash course on why transmission fluid wears out. Although it is not very technical, I thought it had some good information as far as fluid life expectancy versus fluid temperature.

http://ca.autos.yahoo.com/maintain/automatic_transmission1.html


The only other information I was able to find was that transmission performance will be sluggish and shifts will be harsh at excessively low fluid temperatures as well as accelerates bearing wear . The fluid would have to be extremely cold (less than 100 degrees) for those to be something to worry about though. Since you live in a warm california climate (No harsh chicago winters like what I get to experience :smile: ) I doubt that even with the external cooler the tranny fluid will stay below 100 degrees for long. As long as you are running at least 150 consistently I'm sure you will be fine.

As far as having excessive cooling goes, I think the setup that you have is just fine. If the fluid temperature stays too low for most of your driving, you could always move the cooler behind the radiator so it gets warmer air flowing through it. The fan that you installed is a really good idea too to protect from extreme temperatures if you tow with the car. 190 seems like a good temperature to have it set at and I'm sure the transmission will thank you with a very long service life.

I definitely know what you mean about regurgitated myths, lol. I used to get a good dose of them daily from customers way back when I worked in a garage in high school. I can't even begin to cound how many times I heard that synthetic oil is so slippery that unless it is used in a brand new car is will all just blow by the rings and ruin the engine.

Good luck and let us know what kinds of temperatures you are seeing once you get the gauge installed!!!!

Excellent! Thanks. I'll let you know someday on the temp, but the car is currently stripped waiting for an acid dip :) It might be a while :)