Minimum ATX operating temp

[SHOZ]

I use Amsoil ATX in my '97 Taurus SHO. I have added a large cooler to keep the temps under control while I road race it in the summer 3 or 4 times.

Now that it is getting cool out the ATX fluid temps are seldom above 140F. Is this too low?

 

[Bio-T]

You should not have any problem running at 140F. My guage starts at 140F and I never see it move all winter even if I am towing. And rarely above 145F in the summer. There is no combustion for the fluid to deal with and no blowby. Condensation is not a problem either.

 

[SHOZ]

Thanks

I know that with the newer cars the tranny fluid temp is directly tied to engine performance. I think timing is pulled as the tranny temp rises.

 

[unDummy]

You'll need to reference the FSM to see what an acceptable trans temp is. Shift programming might be temp dependent. If that is the case, get an ATF thermostat. If not, don't worry about it. Cooler is better if you can get away with it.

I haven't heard of trannies that pull engine timing based on temp. I know that engine timing can be pulled to soften the shock during a shift.

 

[SHOZ]

It has been found and I have seen the tranny temp tables pull considerable engine perfomance back. This is with temps over 250F.

Last nigth on my 30 mile highway drive home and the air temp in the lower 20Fs the tranny fluid never got over 120F.

I use Amsoil Universal ATF. The tranny shifts and the TC locks up OK after a few miles.

 

[unDummy]

The tranny won't last too long with fluid over 250F. Instead of pulling power/timing, the headrest needs a backhand 'head smack' feature.

Even with no external cooler, my Nissan takes 5 miles on the highway to 'lock up' and its still around 50F degrees outside. With all the MPG ** out there, you would think that TC lockup would occur quicker. Time to wire in a resistor in place of or parallel to the temp sensor. I hope that the TCM doesn't compare tranny temp to: engine temp, time running, or outside temp. The ECM might have a heart attack wondering why the tranny temp is 150F, when the engine and outside air is below freezing during the 1st start of the day.

 

[Kestas]

Why don't trannys lock up right from the getgo.... why does the car need to warm up? On my 90 LeBaron I believe it engaged once the coolant temperature was warm.

 

[theguru]

Shoz,

If you are concerned about the cooler, do what I seen a few truckers do with their radiators, put a cover over it.

 

[Gary Allan]

quote:

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Why don't trannys lock up right from the getgo.... why does the car need to warm up? On my 90 LeBaron I believe it engaged once the coolant temperature was warm.

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I dunno

..but a I imagine that they use the heat generated by the converter to some advantage before allowing the lock up to engage. I thought that the temp threshold was substantially higher then 150F. I'll check my owners manual. I must admit that it doesn't take long ..even in cold temps for it to engage. I also don't know where it is measured (without looking in the FSM) and where our posters are measuring

The out bound cooler line usually comes off the converter, which probably has the highest heat generating potential.

 

[1040 WreckerMan]

Most cars and light pickups have very long delays in TC lockup because in cold conditions and many slow speed situations with the converter in lockup, it can cause noise/drive train vibrations that customers were complaining about. Most cars and light pickups also do not stay in lockup as much as they could for CAFE reasons mostly and poorly designed converters partly.

The largest producer of heat in small automatics is the torque converter. I have, whenever possible, modified all my automatics to go into lockup about 25 mph and stay locked through all up/down shifts. In my F350 this changed average sump temp from 173 to 100degF. This truck usually never sees a GCVW of less than 18000lbs for 90% of its life and I rarely see anything over 125. I don’t have any reservations about running your SHO with 140degF ATF. Personally I think you are running a great temp, I always shoot for 100-150 in all my automatics.

What really bothers me is, Ford and Chevy have in the past built some of the worlds best automatics so they have the ability but choose not to use it. I think a C-6 or TH400 with an extra set of planetary and a lockup TC would be ideal. I've seen C-6's with 2000HP in front of them outlast the engines, yet Ford's newer 4r100 5r110 many times can't handle the loads imposed by stock engines! Ok, I'll get off my soapbox now,


Patrick

 

[SHOZ]

I do have half of the main cooler blocked off and will probably adjust this to 3/4s or so. So I guess if it goes over 100F and the TC locks up I good to go.

I'd like to add that the only time I've had the +250F temps was when I was using a 190F oil T-stat befor the ATX cooler. I was also using a stacked plate type cooler instead of the older radiator style type that I currently have.

Stacked plate coolers are all overrated IMHO.

Thanks

 

[unDummy]

Its all about shift quality. My TC locks up above 104F. Line pressure is adjusted throughout the entire temp range for "smooth" shifting. Avoiding TC lockup allows tranny to warm up to the best running and smoothest shifting temperature.

Its sounds to me that your oil t-stat was defective. Did you have the flow plumbed correctly? Did you only t-stat the additional cooler allowing the OEM cooler to function normally as a failsafe?

I like stacked plate coolers. But, most that are installed and recommended are too small.

 

[SHOZ]

The t-stat was calibrated to 190F but usually ran a bit over. The cooler was just not in good enough airflow. Once the fluid was up to 190F it could not keep the temps down on the track.

It had a bypass feature and on the highway would keep the temps near 190F once it got warmed up to that.

If I could find one set for 140F or so it would be better.

 

[brianl703]

I think not locking up helps the engine to warm up faster, and maybe it isn't good for a cold engine to run it at a higher engine load which is what would happen if it locked up.

 

[unDummy]

SHOZ, what brand/PN ATF thermostat did you use? I'd like to avoid that one.

Brianl703, The tranny takes a lot longer to warmup compared to the engine. I thought it was for the CARB/LEV spec, but not so. Its all about shift quality, which is a farce with most Jatco's anyway.

I also can lose the TC lookup when coasting down steep hills during the winter. The tranny temp will actually drop too much. Its nothing but a waste of gas soon to be adjusted with radioshack resistors

 

[Gary Allan]

Mocal thermostats can be ordered at lower temps. BAT, Inc

 

[SHOZ]

The one I had was a Perma Cool something.

 

[Gary Allan]

quote:

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SHOZ, what brand/PN ATF thermostat did you use? I'd like to avoid that one.

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quote:

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The one I had was a Perma Cool something.

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Permacool thermostats

 

[Sid]

Isn't that temperature sort of low? I thought optimum temps for a transmission are between 180-220 degrees?

 

[SHOZ]

I used the 1070 t-stat. Can't really blame the t-stat. My problem was one of inadequate cooling. Still, now that I have what I do 190F seems way to high.

We've had some 20F nights around here and with the cooler 90% blocked off the fluid temp will get to around 140F in my 30 mile trip. 180-190F on longer trips with city driving.