Normal Transmission Temperature?

[l008com]

What is the normal transmission temperature for these vehicles?

I was halfway home today with a trailer full of concrete blocks and remembered that the whole reason I got this ODB reader was not to constanatly check engine light codes it was so I could give myself a transmission temp gauge while towing.

So I fired it up and I was right around 170°. It was a little hilly and there was no highway, it was all suburb back roads. It had slowly climbed up to 172° and then I was home. I dropped off the trailer and drove another mile but the temp really didn't move, maybe a degree or two at most.

Is the transmission like the coolant, where it gets up to operating temperature and then normally just says there regardless of how you're driving? Or is it always a steady and unchanging flow of transmission fluid through the cooler, so the temp will always vary based on driving?

What is a normal temperature range? And how hot is too hot? My trailer today wasn't very heavy, maybe 2700lb or so. That ain't nothing, but it's also not exactly maxing out the vehicle either. (i was going to say it ain't nothing but it's not a ton... but it is infact )

I drive quite conservative when I'm pulling a lot of weight. I do this more to protect the trailer than anything, I'm always afraid the leaf springs will snap and leave me stranded. But I have towed as much as 5000lb before and you definitely notice that. I was only going 2 miles with that (a towable 50' lift, super fun to use!) so it wasn't a huge deal. And my boat is only 1900 lbs, you can truly forget its back there when you're towing that little, with a 5.3.

So any thoughts on trans temp, lemme know.
Oh I'm using OBD Fusion on iPhone. I have one whole dashboard page that is just one giant radial trans temp gauge. Perfect for towing!

 

[Blckshdw]

The stock tranny cooler is in the bottom of the radiator, so as long as the transmission temp is lower than the engine coolant temp, you have nothing to worry about. Do you have an aux transmission cooler on your truck?

Being here in FL, I've seen my tranny get as high as 200 after some extended highway driving in the summer, with the AC on, and then hitting stop and go traffic. (no trailer, or heavy loads involved) I do have an aux cooler

 

[Mooseman]

Target temp is below 200f. Above that can shorten the tranny's life. If you do any kind of towing, it's strongly suggested you install an aux tranny cooler.

Transmission Coolers..

Ok, so here I am trying to search through the forums on this subject. And I keep getting lost in threads, I swear I could read these for hours, lol! Anyways, does anyone have a suggestion on an aux transmission cooler (to go along with the stock one from the factory tow package, I think) that...

gmtnation.com

 

[59840Surfer]

The real name for what people are want to call a "transmission cooler" is really called a "heat exchanger" in that it is IN the radiator for two reasons ...

1. to cool the fluid some of the time and
2. to heat the fluid to the same as the engine coolant.

The most optimum fluid temperature used to be as cold as possible --- which was a shame because the first really good fluid was "Flipper-In-A-Can" or a derivative of whale oil. This was Dexron ... GM;s own chemical engineers specified it and it was the absolute best ATF until touchy-feely people decided to ban whale products and then the race was on to find a good enough version of whatever the petro-chemical engineers could come up with over the years.

There was a list of things that went to Dex-2, Dex-3, Dex-4, Dex-5 and there were all sorts of offshoots in those enumerations that took you to Chrysler or Ford or Eurobox vehicle requirements.

OK --- enough history ..... and let the petro-engineers chime in for any assistance they'd like to state.

The very best operating temperature is, therefor, right around whatever the cooling system thermostats can get the engine up to ... in the case of most modern GM vehicles, it's just a few degrees south of 200°F.

Actually --- running the ATF too low in temperature, denies it the opportunity to utilize the chemical additives that are liberated only when the fluid gets to the correct operating temperature.

The "correct" temperature, is, therefore: around 190°/200°F .... or so.

PS --- "Modern fluids" are certainly much better at resisting oxidation (that old bugaboo of early ATF after Dex-1 was outlawed) if the temperature ever gets to 275°F.

It can live at that temperature for a while, all things else being equal --- but working it too hard and exceeding that temperature for any length of time is not only shortening the life of the internal transmission spinning-whirling mystery parts --- but also weighs heavily on our minds as we watch the coolant temperature rise.

FTR ---> I have "occasionally pushed" a Ford F-450 Super Duty baby dump truck, hauling 20,000 lbs of Bobcats and busted concrete over Ortega Highway in SoCal, because I knew it was overweight and I was trying to avoid the scales .... ah! Those days were nuts-o.

It was not uncommon for me to peg the gauge --- and I think it went to 325°F before it went off the face, to the hard right.

Anyway --- sometimes that Ford transmission survived --- but most times it would die --- sometimes marking its unhappiness with what I was doing to it --- by shooting the dipstick out of the transmission so hard that a new dent would appear on the hood and a lot of fluid would blow out when the overrun clutchpack finally blew up/out/sideways.

I always had a few spare transmissions rebuilt and waiting to be installed in the small fleet of 10 F-Super Duty trucks the boss loved because of the Big F on the grill.

I swear --- sometimes I wanted to take out the hexbolts and put wingnuts in their place to speed up the R&I process .... and Velcro --- lots of Velcro.

Truth be known --- they were pretty bad excuses for a transmission ---- too much monkey-motion going on inside and .... I'll quit here 'cause this is a GM site.

/

 

[Know1else]

If you run it over 200, the fluid degrades, keep an eye on it, 190-200 is factory spec normal…getting it lower is better for hard parts but not ideal for fluid efficiency. If you see it over 200 a couple times, change the fluid, add a cooler…before something breaks

 

[59840Surfer]

If you run it over 200, the fluid degrades, keep an eye on it, 190-200 is factory spec normal…getting it lower is better for hard parts but not ideal for fluid efficiency. If you see it over 200 a couple times, change the fluid, add a cooler…before something breaks

The worst offender for heating the fluid, is, of course, the torque convertor.

I run a PWM-Delete valve in it where the convertor is either ON or OFF, nothing in between.

The factory calibration uses a digital signal --- which can create infinite percentages of lockup from almost 100% free to almost 100% hooked up.

I say "almost" because the TCC is designed to slip to allow the engine to get to either a better horsepower or torque band and that allows the engine to max-out the fuel economy and at the same time providing a little SOP feel of the vehicle actually going faster.

Since I had the unit rebuilt to my specs (I'm out of building transmissions since I retired in 2004) I went full-tilt with a Gil Younger Shift Kit, 3" 2/4 band, "Corvette Servo", stacked accumulators, hardened drum, Torrington Roller Radial bearings, etc., etc., and I added a GM 4.3 V6 torque convertor because it has a much larger Carbon Fiber TCC in it.

I also had a much higher stall speed cut into it --- it went from @3500 RPM to @4500 RPM with the GM 4.3 V6 engine as a test bench model. I get about the same RPM changes, but the 4.2 develops more torque so it isn't exactly the same.

INSTANTLY --- my fluid temperature dropped from a "normal" 186°F to 155°F under the same driving conditions. This was without any auxiliary coolers added or even needed.

IF you do the PWM-Delete change, you'll prolly find you don't need another "cooler" to be added to an already very crowded area under the hood.

I recommend it ---- really.