ATF Temp. Too Low?

[Drew2000]

Pulled into a highway gas station after extended high-speed driving and checked the ATF fluid. Fluid was barely warm, outside temp was about 15'F. 3.0L Ford Escape, vehicle has in-radiator cooler and pretty big factory external plate cooler, about 4"x20".

Been checking the ATF temp by feel of hand, and it just doesn't seem to get very warm from local driving or highway. "Normal" temps for ATF is usually 170'F. I know that engine oil is supposed to heat up to proper operating temps, but was wondering if cool fluid is bad for a automatic transaxle? Maybe a piece of cardboad over external cooler during very cold weather? Maybe get a life and stop reading all this BITOG stuff?

Drew

 

[sifan]

Driving continuously under such a cold temp my ATF temp gauge's needle won't even move. But, if you get stuck in a traffic jam in the middle of trip for 10 minutes, the ATF temp will rise to around 120F and stay there.

 

[SteveD2]

I would not worry about the "too cool" temps...as long as you are getting normal shifting after it "warms up"...your fluid will last a long time...

As a side note, my 99 2500 CTD truck would not even pull the guage off the 100*F mark when it was below 40*...

steved

 

[1040 WreckerMan]

In cooler temps, less than 50*F or so, most of my stuff doesn't get much more than 100*F sump temp, and that's if you are working the fluid a bit. It takes a good bit of time to get over ambient temps.

 

[Jim Allen]

1040 Walmart touches on a good point. Where is the oil temp measured? It makes a big difference on the readings. Some measure from the sump... a logical spot. Others measure in the line out to the cooler. Still others measure the temp in the line back from the cooler. In one of my rigs, I had sensors in all three places for tests, with a rotating switch, and they were widely different. The out line was always the hottest. On my transmission, it was oil flow from the converter, so that stands to reason. A typical reading could be 120 in the sump, 250 at the out line and 130 from the cooler (it ran through the radiator into an oil to air cooler and back into the trans. Many trans companies, however, advocate sensing in the return line because that is oil is usually used to lubricate and cool the hard parts. I'm an advocate of a sensor in the pan because that where the oil is picked up, but I can see the point of knowing the other temps as well.

 

[Tempest]

I would think that the out line temp would be the most valuable because it will give a true picture as to how hard the trans and fluid are being worked. The other area's temp are valuable information though.

 

[1040 WreckerMan]

Jim Allen, I have temporarily installed more temp senders in a couple of my trucks just to see what was going, it's kinda fun. Normally all I run is the sump temp.

In most automatics the flow out to the cooler will be about 25% (more or less depending on application and size) of converter flow. This will always be the hottest oil. Since the TC is pretty tolerant of high temperatures, and only about 25% of the flow leaves and goes out to the cooler I don't find this a useful reading for anything other than measuring the efficiency of my cooler assemblies.

The return from the cooler to the transmission will be the coolest temps seen (if not you'd better start looking for a good trans shop!). As Jim Allen said, this return flow is normally used to lube the tailshaft gearing. Most trans failures that I have seen are from either clutch problems, or an engineering flaw and their is material failure. I rarely see lube related failures, especially from high temps. Surprisingly the portions of the transmissions that are lubed by cooler return are really tolerant of fluid temp (not true of many other trans components).

Sump temp is, IMO, one of the best places to measure temp. The sump is where oil is pulled from. This is the temp that the pump and pump seals will see. After being pumped it will be slightly higher in temp (although not considerably) and this is the temp that the clutch packs and some lube oil components will see. This is also the temp oil that will enter the converter and help cool it.

My experience is mostly with medium and heavy duty transmissions, although the information applies to any automatic some of this may be a bit different for light duty. The smallest transmission I've worked on in a very long time is the AODE and 4R44E transmissions in Ford pickups. Mostly I work on Voith, Allison and CAT automatics. The major differences as far as temps go on these larger units is most have full flow coolers such that all of the converter fluid is sent to the cooler.

 

[Titan]

WreckerMan,
Do you think I'm doing myself a favor by drain/filling the ATF on my two Subarus (4 speeds) every 15000-20000 miles? Or, am I just wasting money to do so? The fluid I drain out is browner and certainly is thinner...then again, it's warm when I drained it! But, come to think of it, once it cooled and I poured it out at the recycler...it was certainly thinner than the new Subaru fluid I put in. One is a 2006, one is a 2007, and I'm driving 30000 miles a year on EACH...I just want the transmissions to last as long as the engines...hopefully 1/4 million miles each. Thanks.

 

[PT1]

My Gm trucks will take a long time to pull the needle off 100* in the Winter. Usually takes 30-60 minutes of stop n go driving just to get it to register.

 

[unDummy]

Its never a waste of money to drain/refill every so often. Either use mileage or time to choose an interval.

Titan, with a 30k yearly on each(wow), I'd definitely drain/refill every 6 months or 15k. The transmission should last forever with that maintenance if driving style isn't abusive. Consider a full synthetic and extra filtration if you want to just maintain it every 30k/yearly.

Automatics in the winter tend to run cool. Some cars won't upshift in OD or won't lock the TC if the transmission is too cool. If using a blend or synthetic, I wouldn't worry about the temp being too cool. I would worry if using a mineral ATF which might not pump or flow too well causing the transmission to be less responsive.
If you have an aftermarket ATF cooler or upgraded OEM cooling and don't believe its necessary for your winter driving, feel free to block it off with a piece of cardboard during the winter.

I agree that sump temp is the best for temp measurement. Most transmissions with temp sensors measure the ATF temp in the VB straight from the sump. The best average temp is there.

 

[Titan]

Thanks for the recommendations. Yep, that's 30K per year each. They are either driven highway at about 70 mph, or small town city. Both fairly easy on a car. Don't think I'll worry about extra filtration...they do have a removeable filter (like an engine oil filter), maybe I'll change it every 100,000 miles. But, the big question I now have is: with seemingly every manufacturer saying don't mix the different fluids, and with me only draining/refilling...should I go ahead and mix? Or, do I have to go to a shop to get a true exchange the first time? Thanks!

 

[unDummy]

The OEM filter is cheap enough to change out every 30k if it is a spin on. You can get the dealer parts cheaper online or just use the purolater/wix equivalents.

It is perfectly acceptable to mix like fluids.

Since you have a drainplug and an external filter, I would never waste money on a flush. There is no need to ever flush if you pull that drainplug twice a year and replace the filter once a year.

What fluid is required for the 2006? the 2007? What ATF do you plan on using for both?

 

[Titan]

Same fluid for both of these 4 speeds. They have a different recommendation for their 5 speed. I just bought the Subaru brand ATF (I got a discount since I bought 16 quarts), but, I'd like to switch to a full synthetic. They list about 4-5 different acceptable fluids, including Castrol Transmax J, Pennzoil ATF-J, IDEMITSU ATF HP, or the Subaru Type HP. I wanted to put some SF auto transmission fluid in it, since I have their gear oil in my differentials, but, they were closed when I asked what fluid worked well in these 4 speeds. Thanks for the advice!

 

[unDummy]

Is the above fluid recommendation for the 4 or 5 speed?

 

[Titan]

4 speed.

 

[1040 WreckerMan]

Titan, as unDummy said, you are money ahead to change the ATF frequently. I wouldn't worry too much about mixing fluids. I'm not a big fan of flushing machines, and I'm much too lazy to do the cooler line flush method. I just drain the pan in most of my stuff, about every 15K or so. Quick, easy and you are constantly replacing enough fluid that the trans will stay happy for a long time.

With ATF, there aren't any combustion byproducts. All that you are worried about is shearing and additive depletion. Frequent "pan drops" keeps the fluid close to the correct viscosity and renews the additives. Spin-On filters are a good idea IMO. I don't even bother to change the internal filters on my personal stuff unless I pull the pan for some other reason.

 

[Titan]

Thanks Wreckerman. Although I re-built my first vehicle from the brake system to reassembly of much of the engine (the parts were handed to me in big wire baskets), I took the gearbox to a remanufacturer and exchanged it for a rebuilt one. That's the closest I've come to working on a transmission, and the automatics are simply a mystery box to me. I've looked at the diagrams of planetary gears, seals, etc., and I just don't understand it well enough to know what really needs to be done to them to make them last. I'll do the 15000 mile changes, and gradually move over to 100 synthetics by mixing 3.5 quarts at a time. I think these two transmissions hold 9.8 quarts...I also understand they're considered to be fairly reliable...I just hope I can make them last as long as the engine. Thanks again!

 

[Drew2000]

Thanks for the replys. Since I'm running plain Mercon/DexIII non-syn and weekday commutes are fairly short (10-15mi) I thimk I'll block off the external cooler during very cold weather to allow the ATF to warm up a bit more.

Drew

 

[C.S.]

I measure my ATF temp as it comes out of the TX for this reason: High temps kill the fluid. It doesn't matter what the average temp of the fluid is, it is the highest temp that it experiences that ruins it.