How cold is too cold for a tranny
 

It is quite chilly in PA for this time of year and my SVX is running quite cool as far as tranny temps go. Went to my rents house for T-giving and it didn't get above 120 degrees for the 100 round trip. I know cool is good but cold isn't. How cold is too cold for transmission fluid. I drive the 15 minutes to work and some mornings its just reaching 100 degrees when I get there. It'll only get colder right! Subie says normal operating temp is between 140-160.

Hi benebob,

It has been cool out lately:cool: I have a transmission cooler and I measure the tranny outlet temperature going to the radiator before the cooler. I have noticed that the tranny takes a long time to get warm these days. This morning with an ambient of about 20F the tranny only got to about 145F by the time I got to work. That's even with driving at 60 to 80 mph for about an hour and a 1/2:)

I use TC lockup to judge the tranny temp. IF it locks up, then the fluid is warm enough. I also expect the tranny to lock up after about 20 minutes of driving. No problems this morning.

For those days when it is colder out I shut off the external cooler with a diverter valve. This bypases the external cooler.

The other thing to remember is that the fluid in tranny pan is colder than the fluid coming out of the tranny on the way to the cooler. The fluid coming out of the tranny has just gone thru the Torque Converter. This makes it hotter than the pan fluid.

I think it is a good idea to fully warm up the tranny before doing any hard driving in the winter.:) I think your gas milage may be poor since you drive a short distance. Try letting your car idle for about 10 minutes before you drive off.:) This may improve your gas mileage. :)

I couldn't find any good info on too cold for a tranny with a google search but in my experience a quick hillclimb in 3rd gear will raise the tranny up enough to hit normal temp adn beyond. I can't imagine it would be good to stay too cold though, need to get hot enough to roast off any condensation.

I was driving my car for a little while with the engine under guard thing removed before I took it to get painted. I didnt observe the temp go above 120 the whole time, even after hours of driving. This concerned me.

Mike

I've been interested in this topic, and have read some anecdotal evidence that says about 160F is the ideal. A paper from the automotive section at LSU says most automatic transmission OEMs don't try for TC lock-up until above 120F (of course ours is about 150F).

The only factory spec on minimum temp I've come across is from the GM truck division which says NOT to operate with dexron III filled transmissions below -13F (-25C). They suggest a pre-heater or let it idle until the ATF reaches that temp. I'm presuming that the fluid is too thick below that point to effectively flow to all the proper places (not stated in their paper).

P.M.'s
 

Lee I have sent you two PM's on 27 & 30 Nov. Message tracking indicates these have not been read. :confused:

Totally
 

Interesting topic. I am having a B&M 19000 lbs cooler put on mine, because it has just fried the second tranny since I've had it. Brake band and clutches burnt, lock-up fried[hence higher consumption]

Climate is temperate here[i.e. wet!] we never have the low temperatures you mention. My high temperatures are caused by stop-start city driving, rather than ambient problems.

Presuming the OE cooler is unclogged[later models without turbolator], in theory the original liquid/liquid intercooler is the better solution. The engine should lend heat via the radiator coolant to quickly bring the tranny oil up to optimum temp. A divert valve to shut off the oil from the additional cooler is a really, really good idea, and use the OE one in the rad for cold winter driving.

If this is not possible, as in where the original has been bypassed, then the old method of putting cardboard or some such in front of the new cooler is a very good remedy. Obviously be sensible, and only block off maybe half of the front surface, some cooling is required. Also don't forget to take it out in warmer weather, and don't come cryin back to me if the thing cooks because you forgot to remove the shield!!:D :D

Joe:)

Re: P.M.'s
 

Sorry, usually the forum has a pop up message when I get a PM, something must have changed. I hadn't seen any posts by you and thought maybe you were on holiday. I have read your answers and thank you for your time and consideration. I will follow your advice and see where it leads me.:)