Thread: Transmission Fluid Thermostat

So I have been thinking about putting a thermostat on the line going to my transmission cooler. For the sheer reason of mornings like today where it is close to 0° and I have to drive 50 miles to work, half of the trip on the highway. And the tranny temp doesn't get much over 100°.

So I thought about getting something like Perma-Cool has. Summit Racing has them for $41.88 and they seem like a good idea. They would let the trans warm up and stay near 180°. At the same time, I would bypass the radiator cooler, and run all hard lines with fitting, instead of hose clamps.

Any thoughts?

I think with something like this. Location is going to be key. Good idea not sure if it's worth the trouble though.

Originally Posted by 19SE92

Its not worth it if that fails then thetrans is fried. your best bet is let the car warm up a good 20 minutes before u head out

Wow... I start the car about 2 minutes before I leave in the morning. And I notice a decrease in gas mileage as to when I don't do this and just get in, start and drive. But I think even a little bit is beneficial.

And sure 20 minutes might be better for the transmission, but constant idling is not good for the engine...let alone the amount of fuel you will burn in that time. I'm not poor, but damn I cannot afford that much!

Edit: Also, you can say that about any part. Almost anything can fail and ruin your engine or trans. Maybe I should take off my trans cooler. It could fail and cause everything to grenade. And the cooler in the radiator. What do I do about that?

I am vigilant on how my car drives 99% of the time. If something is failing and my trans is heating up, I will most likely know it. I run my PT and scan about 80% of the time. And if it starts overheating, it will drive and shift differently, and I will recognize that.

Sure it's a gamble to install it. But one I think is worth it...

To say nothing of the fuel washing of the cylinders at that time that tends to accelerate wear because the fuel dilutes or washes the oil from the cylinder bores and the fuel that gets into the oil itself that if you dont drive it long enough to get the oil up to temperature and evaporate it out, causes lubrication issues by thinning out the oil too.

I think its a wonderful idea. Its like any other added connection, if you think it through and do a good job, it will provide trouble free service.

Zef, if you do this please document all you can. Im getting ready to yank my tranny and I think I may take a serious look at doing this myself.

I always let my work truck warm up for atleast 25-30 minutes this time of year. When I leave, I will go out and start the GF's GTP and let it warm up for about 15-25 minutes each morning. Its not going to hurt anything, but it can help things.

The work truck, a 2004 Ram 1500, has coolers for everything. Transmission with a separate fan, power steering, and of course engine. I don't block off any of those coolers on the front during the colder time of year. I just drive it. As my co worker says, "I never scrape my windows in the morning...thats why they give these trucks such big fuel tanks".

As do I...I go out, crank on the defroster, and go back in side.

You can drive your car with a minimum amount of transmission temperature, just don't flog it!

You want a bare minimum of 170* before you start flogging on your car, WOT runs etc.

Winter time...I dont see many doing this, so drive smart, and easy on the car for your trip to work and you will be fine.

What I do on my GTP, is I will shield the after market inline cooler I have installed from letting air pass through it. It will still cool, but not as much, thats what I want. I only do this is the out side temperature is so cold, and will stay cold while I am driving. With out it, the transmission stays way too cold IMO, with it, it warms up, but not as hot as I would want it to, but then again, I am not doing WOT runs when its that cold out.

Food for thought.

~F~

I received this truck with 6 miles on it new. That was in 2004.

Its now 2008, and I have 226,000 miles on it currently.

At 100K it had a tune up, and a transmission pan drop service. NO FLUSH.

Only things I have replaced on this truck that failed or leaked:

1. rear diff. drive shaft seal = leaking
2. right front wheel bearing = knocking
3. 2 sets of brake pads
4. 2 or 3 sets of tires
5. routine stuff like air filters, windshield wipers etc.
6. oh and 2 light bulbs for the rear tail lights.

Been a pretty stout truck all these years.

Only time it went in to the shop for a major repair...a ground was bad for the dash cluster, and the ABS unit under the hood got wet, both on the same day. (roads were flooded) Other than that...nothing major.

~F~

Originally Posted by GR8racingfool

I always let my work truck warm up for atleast 25-30 minutes this time of year. When I leave, I will go out and start the GF's GTP and let it warm up for about 15-25 minutes each morning. Its not going to hurt anything, but it can help things.

You must have more money than I do. I don't have the kind of cash to let my car warm up for that long.

Company work truck = free gas.

The GF's car is completely stock, been doing this for years, with no ill effects. Her MPG hasn't dropped that much with letting it warm up like this every morning. Yes, it has dropped, but not so much its going to break the bank.

~F~

Any kind of restriction in the cooler system will trash the trans in a matter of miles. The return fluid from the cooler is the mainline lube feed for all of the geartrain and blocking this will not only cause severe loss of lubrication needed to all of the bushings and bearings and geartrain but also will damage the torque converter and lockup clutch. Trans fluid a LONG time ago was different, the fluids we have today are designed to work in extremes, especially the new dexron 6 fluid. Back in the 80s and earlier transmissions were all hydraulically controlled and if the fluid was too cold or thick and the parts were too cold shifting characteristics suffered sometimes until the vehicle warmed up. Since everything is electronic now that really isnt a concern and the fluid lubrication properties have come a long way. I personally dont even want to see the gauge hit 180 but hard driving and drag racing does put a lot of stress on things. As far as vehicle warmup there was an extensive research study I came across a long time ago in college about this and each manufacturer put in there $.02 and all said it was best NOT to warm your car up and start driving it. Letting the car sit and warm up will take longer to warm up and the big factor was that when the engine cold it runs richer and puts out more emissions, also with the transmission sitting stationary nothing is making much heat and takes even longer to warm up than just hopping in and driving. Sure nobody likes jumping in a stone cold car and going anywhere but all the manufacturers that spoke of this agreed it was best for the car and from an emissions standpoint to have as minimal warm-up times at idle as possible.

Originally Posted by Trannyman95

Sure nobody likes jumping in a stone cold car and going anywhere but all the manufacturers that spoke of this agreed it was best for the car and from an emissions standpoint to have as minimal warm-up times at idle as possible.

learned something new everyday. since i have a remote starter i have a tendancy to start it and let it 'warm-up' for like 6-10minutes then head out, but i might as well lower the amount of time after i start it then head out.

Back in the 80s and earlier transmissions were all hydraulically controlled and if the fluid was too cold or thick and the parts were too cold shifting characteristics suffered sometimes until the vehicle warmed up.

Boy I remember my 1st car, an 1987 Cavalier with a 5 speed. When it was cold, the clutch fluid would set up so stiff, you had to sit there in the drive way holding in the clutch and the brake, and the gas at the same time to be able to ever get it out of the parking gear.

Once it was warm enough to take two hands to pull it out of gear with all your might, the fun wasn't over...I had to block the wheels with a block of wood because the e-brake didn't work. God how I don't miss that car LOL.

My sisters 1988 if it wasn't warm enough it would just shut down on her while at a stop light all the time.

Main reason why I warm my truck up in the morning is not to make it warm inside or things to shift or run better, its because I don't want to scrape my windows.

~F~

Originally Posted by GR8racingfool

Main reason why I warm my truck up in the morning is not to make it warm inside or things to shift or run better, its because I don't want to scrape my windows.

~F~

x2

Main reason why I warm my truck up in the morning is not to make it warm inside or things to shift or run better, its because I don't want to scrape my windows.

I side with that!!!

Originally Posted by 19SE92

Its ok to let the car sit and warm up. Why do you thing there is open loop and closed loop fueling. And why do you think there are thermostats out there.If it was ok then cars and trucks would not had thermos in them. A car or truck will run as its best when its up to operating temp. but the mpg will go down some but everything will beworking and flowing right.

So we have thermostats so people can let their cars warm up in the winter?

Um, might want to rethink that.

But Dave, thanks for the input on the fluid flow. I didn't think this would restrict the fluid flow that much. And I figured with upped shift pressures, it would make up for it. And I agree that I think 180° is a little high and I wish the t-stat would be adjustable. So the more I think about it, the more I don't think I will do it. But it was a good idea, and some good conversation.

Thanks!