View Full Version : Trans fluid too cool???

10-06-2008, 06:28 PM
Been driving the 89 for a few days and everything is checking out ok...but I'm a bit concerned about the trans fluid temp. I have a 28k gvw stacked plate cooler from B&M, MAC deep trans pan and the GM airdams sandwiched in the front bumper....so it keeps really cool...but I'm wondering if it is too cool.

Lately with the colder weather (no more than say 75* F) it takes about 30 mins of driving to see the trans temp at 180* (via autometer trans fluid temp gauge). I have read that 180* is the ideal temp for the fluid but i would say 90% of my driving is less than 30 minues...so i rarely get to see the fluid temp get that high. The one time in the past week that I did see it I had to make my self drive around town.

This will probably be beneficial during longer trips or during the hot weather months, but I'm wondering if it will cause a negative effect during these cooler days. I think I remember reading that there is some sort of thermostat valve or something like that which will hold the fluid before the cooler and allow it to get warm. Would this be necessary? Any thoughts? Thanks!

10-06-2008, 08:10 PM
Sorry if I missed it - where is the trans fluid temp sender located in your system...?

One of the nice things about auto trans fluids is their service environment latitude. I doubt your car will ever see a range that is too cold...

10-07-2008, 09:59 AM
there was a plugged port on the side of the transmission where several people have put the sender....thats where I put mine too. You simply remove the port and it's just the right size for the autometer sender.

10-07-2008, 09:59 AM
the cooler you can keep the trans fluid the better!!! Heat is definitely the destroyer of both fluid and clutch discs!! Anything you do to keep that puppy cool is going to lengthen the time your trans keeps going.
I have a cooler on my Ranchero, it only gets to 180 on trips greater than 45 minutes. Not had a problem in 6 years and the fluid stays nice and red!!!
I changed it last spring and it looks just like it came out of the bottle!
So-o-o-o-o Keep it Cool!!!

David Neibert
10-07-2008, 12:42 PM
The cooler the better.


10-07-2008, 06:33 PM
That sounds good...in that case I can go ahead with my plan to put another B&M cooler in series and add a fan :). I remember seeing this set up in someone else's car. Should be my last trans upgrade before getting a Lentech valve body.

10-07-2008, 06:46 PM
Like the motor there is an optimal temp, and running the coldest isn't always the best. Our tranny's where designed to be optimal at around 180 or so from alot of sources I've read. Go too cold and you get harder shifts that are hard on the internals, and go too hot and you start slipping and buring stuff up.

If your running a 180 tstat and have a chip that sets up your fans properly, then after the trans cooler you should route through the rad to bring the temp to optimal so to speak either down or up.

In the later cars with the 4r70w, there is temp variations in the transmission itself that affects your AFR and your spark with the EEC.