I am interested in feedback on what is an acceptable transmission fluid operating temperature, as well as a typical range and maximum.

I drive a 1990 F-150 with a 351 block, E40D transmission with a Banks Transcommander, oversized radiator, transmission cooler, and 3.73 rear end. I recently installed a temperature guage for my transmission fluid with the intent of guarding against overheating.

Any observations and headsup you can provide would be greatly appreciated.

 

Anywhere between 175-190 would be the typical range. I have seen temps above 220, but that temp really plays hell on the fluid life. That temp was in my dads Chevy with an automatic tranny, before a cooler was installed. His temps have dropped about 20 since we added the cooler. Putting a cooler on the tranny is the first thing I would do to an automatic.

 

The Manual says the normal operating temperture is 140 to 170 degree's. Above 200 the degredation of the fluid begins and therefore the fluid begind to break down and not protect the tranny eventually. After 250 the fluid breaks down quickly and above 300 and it is almost immediately toasted.

I try to keep my tranny temps below 170 if possible. I would change to full synthetics if you wnat a fluid that can handle 200 degree temps longer than the sysntetic blends Ford uses.

I have installed a 8 inch Fan on my stock auxilliary tranny cooler that gives me a consistent 10 degree drop when turned on. When my tranny approaches 170 I turn it on and get back down to 160 or less even when towing in 100 degree weather. I just got back from towing my travel trailer to Savannah Ga. in just such conditions and found my fan to be very helpfull. With it on, I ran 155 to 160 consistently. Off, I saw it creap up to 170. Takes about 10 minutes or so to see the drop. I turn it on when i hit a town or have to slow down for a while but I also saw good responses at full out 65 mph in thiese 100 degree plus temperatures. I spent $75 doing it.

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2000 F-250 Super Duty, SuperCab XLT, Oxford white with medium grey cloth captains chairs, 5.4L Triton V8 (260 HP - 345 FP Torque version!), 4R100 4 Speed Automatic Transmission, 4 wheel ABS, Deluxe Aluminum Wheels, Trailer Towing Package, Class IV Hitch, Reece load distribution system, Escort Sensor II Electronic Brake controller, Sure Stop towing skirt, "Westin" black powder coated step bars, "White-White" head lamps, Herculiner bed liner, ISSPRO Tranny Temp Guage, Excursion center console, Ford moulded mud gaurds, K&N Air and Oil filter, Amsoil XL7500 5W-30, Air filter minder, Perma Cool 8" (800 CFM) Tranny Cooler Fan (manualy switched).

 

Thanks for the input. Now for an update.

After a week's worth of observations, I have noticed a very peculiar phenomenon with my transmission temperature. I can drive for an extended distance on cruise control, maintaining a very consistent temperature of 180-195 degrees. Then at an eventual point, my control becomes disabled, which seems to occur when the outside air temperature is around 80-90 degrees. This happens pretty consistently, so I assume there's a safety reason for it. Now here's the weird part.

The moment I use the foot pedal for throttle control, my transmission temperature begins to steadily climb until it becomes necessary to pull over every 20 miles to let it cool off. The sharp temperature increases are suspiciously coincidental with my foot throttling, although I am intentionally light-footed.

Has anyone run into this before? What should I be looking for?

 

That is not normal as far as I am concerned. It sounds like your torque converter is not locking up maybe? It is possible your temp sender is not grounded properly and giving false readings but coupled with the performance issue of the cruise control I don't know about that.

 

Do you have an auxiliary fan on your oil cooler? Most of the later model vehicles will shut off the radiator fan at cruise(unless the A/C is on, it cycles with the compressor)
I would put on a small fan that is temp controlled to make sure it runs when oil temps get above 180°F.

 

How steady are you with your foot? If you let the throttle close all the way the torque converter will unlock. It will then slip again when you open the throttle. This slip will generate heat.

The cruise control will usually hold the throttle steady and keep the converter locked.

Mark

 

Those of you using a fan on the transmission cooler could impliment a snap disc thermostat to automatically turn it on at say 170 and off at 150 or so.
Just an idea so you don't have to monitor the temp gauge so closely.

 

Wirechief...

I too have noticed that outside air temps play a key roll in trans temps. And there is some explanation for this, at least for my truck. Anytime the air temp is above 68-72 degrees, my Water temp climbs to around 200. Now this is important because in my truck the trans cooler lines are routed through the (h2o)radiator first, and then through the trans cooler. So that little trans cooler has a lot of work to do. Even with a fan on my trans cooler, on hot days, I am fortunate to keep the trans temps just under 170. As for using cruise control, it will keep your temps much more stable, but an increase of that amount (to 190) seems out of line. Hope this helps

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2000 XLT Silver 5.4L SC 4X4 ORP 157"wb Ford Floormats, Mudguards, lighted emblems, lighted interior door handles(all 4) Chrome Grill (4x2 style), Diamondplate bed caps, Pro-Tech tool box, Air Box mod, Muth Signal Mirrors, Custom Gauge Pod

 

How do you guys monitor your tranny temps.?

-AR

 

You install a guage and sender. Here's some pictures of it. Its a pretty cheap thing to do. Can be done for $50 or so. Want more info? Do a search! It's all here. Parts numbers and suppliers as well. You can contact me if you need help.



Here's some more pictures of the install. Locations of guage and senders are debatable and optional.
http://albums.photopoint.com/j/Album...3146&a=4739786

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2000 F-250 Super Duty, SuperCab XLT, Oxford white with medium grey cloth captains chairs, 5.4L Triton V8 (260 HP - 345 FP Torque version!), 4R100 4 Speed Automatic Transmission, 3.73, 4 wheel ABS, Deluxe Aluminum Wheels, Trailer Towing Package, Class IV Hitch, Reece load distribution system, Escort Sensor II Electronic Brake controller, Sure Stop towing skirt, "Westin" black powder coated step bars, "White-White" head lamps, Herculiner bed liner, ISSPRO Tranny Temp Guage, Excursion center console, Ford moulded mud gaurds, K&N Air and Oil filter, Amsoil XL7500 5W-30, Air filter minder, Perma Cool 8" (800 CFM) Tranny Cooler Fan (manualy switched, Deflect-a-Sheild Aluminum Dimond plate Tool Box.




[This message has been edited by cphilip (edited 08-15-2000).]

 

Damn, that's cool man...thanks for the info.

-AR

 

Well, this saga seems to take a few new twists all the time. I asked the shop to perform a transmission service, as it was about due for one anyway.

Upon inspection, the fluid was absolutely clear and there was not a single speck of anything sitting in the bottom of the pan. They did, however, notice a shortage of fluid when it was drained. This puzzles me because I was very diligent in checking the levels two weeks ago at various points during my trip. I observed no smoke, nor a single drip mark in my driveway, so I don't know where it went.

I am hoping that I can simply blame this on the possibility that I did not know how to properly check the fluid levels, afterall. If this is true, a low level condition would explain the irratic heat symptoms, even though all shifting appeared normal. The ironic thing was that my engine temperature ran cool enough for me to be able to place my hand on the radiator cap, and LEAVE IT THERE!

Knowing that I now have the correct fluid levels in my transmission (with a little egg on my face), I will have the opportunity to tow under load and observe during the next few days. I will report my results.

 

Interesting. How did they determine it was actually low? Not by how much they drained I hope. If they did not drain the torque converter they would only get out about 3-4 quarts. And leave a lot in the TQ as well as the cooler lines. Did they do a complete flush? Thye should have seeing you are having problems. It could be that your auxiliary or intregal cooler are partialy clogged too and a flush would ahve eliminated that. But that being said, clear, non burnt smelling fluid is good though. Very good.

You cannot check fluid levels until at operating temp of 140-170, as you now know. And you now have the temp guage to determine that. So you are better off now.

Keep us posted how your temps go.

[This message has been edited by cphilip (edited 08-17-2000).]

 

Nope... I am not going to tell you that consistent temps of 185-195 are normal. Should be 150 to 160. I suspect your sender or guage itself is not grounded properly or your tranny cooler is partially if not completely clogged up.

I have never heard of a drop or gain in temp happening immediately. It usually takes 10 minutes or so. I am very suspicious of your guage itself for that reason.

Try reseating the sender (back it out a few turns and then retighten carefully to get a better sender ground) and checking the ground wire to the guage itself and then, if not responsive, then having your whole tranny system "power flushed". You should see 150 to 160 unloaded in hot weather.

[This message has been edited by cphilip (edited 08-22-2000).]