Im just curious about everyones opinion on this.

I just bought a large B&M cooler, but I live in Maine and over cooling could be an issue, so I also picked up a perma-cool thermostat. I Haven't heard of a lot of people running these so I thought I would give one a try. The only problem is that it doesn't open until 185 degrees.

I see a huge range of numbers for what is considered "safe". Some folks wouldn't dream of letting their fluid get above 160, while others say you are good until 220 or so. My manual lists normal operating temperature for checking the fluid level at 150-170. Keep in mind the thermostat will be just down stream of the torque converter so that should be the hottest fluid the transmission sees.

So is it better to run it at 185 or let it run below operating temperature?

 

Keep in mind 185 is when the thermostat opens up that should be the highest temp you see. I find that acceptable. I liek to keep them a little cooler but if the trans is working properly you will find the fluid isn't that hot anyway.
Alan

 

You didn't provide any information about your vehicle. However, all automatic tranmissions in the f-series trucks have an oil to water heat exchanger built into the radiator. In trucks with the towing package or the super cooling package (or the heavy duty payload package IIRC) they will have an auxiliary cooler mounted between the radiator heat exchanger and the transmission in the return line to further cool the fluid.

In a standard vehicle, the trans fluid will come out of the radiator heat exchanger at roughly 200 degrees. It'll cool a little bit returning to the trans, and even more-so if it passes through an auxiliary cooler on the way. IMHO, there's no such thing as too cool for the trans fluid, but 240 coming out of the trans isn't pushing it if you ask me.

-Joe

 

I have a 2000 f-150 (just bought it the other day actually). It doesn't have the tow package so there is no auxiliary cooler, only the one in the radiator. I plan on bypassing the heat exchanger in the radiator though, which is the reason I bought the thermostat.

BTW, I am basing my assumptions off of my old explorer. It had a large B&M cooler (can't remember exactly how big) that bypassed the radiator and the trans temps rarely reached 120 degrees in the winter. And for that to happen I would have to be driving in town for long time.

So, I basically have the choice of running the thermostat and keep the temp at 185 most of the time, or not use the thermostat and have the transmission running below 120 degrees 90% of the time. I could keep the radiator in the loop, but Ive never liked that idea very much.

Thanks for the opinions, keep em coming

 

http://4x4trailhunters.com/article.php?id=21

A little tranny chart something too look at!!!!!!!!!!!

 

From experience here; why not let the engine radiator cooling section control your overall temp instead of trying to re-engineer the operation?
First, at temps just below 100° in the pan area, the transmission will be prevented for going into overdrive by design. If you over cool in winter temps you have a long heatup time before OD can be used.
Second you should not run to low a temp from a lube stand point.
Third, the fluid is good for close to 240° and can get over that temp in the converter under certain hi load conditions.
IMO you may get yourself out side these overall ranges unessasarly.
I would leave the radiator in the loop for three reasons. You get automatic temp regulation by the radiator, faster warm up of the fluids for cold weather and not use any temp control in the aux cooler unless you know how this is all going to work out or follow a known installation for your application.
Using trans temp gages and what they will tell you depends on where you are measuring temperature.
I run an aux cooler with the radiator in line at engine temp and monitor at the output of the converter before the radiator. Normal unloaded running temps are in the 140/145° range at all times until heavey towing is done then things get a bit higher as would be expected. No under heating no overheating.

 

Yes, you make a good point. At first I was aginst this idea, but I have actually been thinking about this for the past couple of days. It does seem like it will be the best solution. Especially since the heat exchanger is on the cold side of the radiator, i wasn't aware of that. With a 180 degree thermostat it would probably even help to supplement the auxillary cooler under towing condions. Ive got my new pan, and a seperator plate on the way. I'll try and post back to this thread in the future to as to what the temp does over some different conditions.

FWIW, the cooler is a 20,500BTU B&M unit (not sure what that is in GVW), and the temp guage is an autometer ultra-lite electric, mounted down stream of the converter.