Transmission Temperatures

[dznf0g]

I believe one has to have the DIC for a trans temp gauge.....generally. There were some work truck trims that had it as a function of a push stick in the dash (think odometer, trip button). The data is available at the ALDL for everything, but the upscale DIC is required for a digital readout. Gauges are in some vehicles, depending on model.

[chaseav]

So I called GM today. Not surprisingly, they had a mildly difficult time understanding what I was even asking for. The rep did not have the answer and admitted that but was helpful enough to call my local dealer for me. After about a 15 long phone call, the answer I received was:

According to the Parts Department Manager, the transmission temp warning light will come on at 270-280 degrees depending on a number of factors. (I could probably put quotes around that but truly I'm paraphrasing.)

I replied, "so that temperature would be considered the temperature at which I would start doing damage to my transmission."

The answer, "yes, that's what I interpret that to mean."

So there we have it folks!

[RareStream]

Once a transmission hits 270 pulling a trailer up a mountain damage is already done and thousands of miles are deducted from the usable life of said transmission.

[ROBERT CROSS]

Originally Posted by chaseav

Since 2007, they started putting the trans temp as a digital only readout within the same DIC that displays your odometer and whatnot. So no red arc unfortunately, just the number... and mass confusion.

"Steam" is the term we use in aviation to describe any gauge that has a mechanical needle. Those have all but been replaced now by computer screens which merely simulate them. When there are dozens of them to display, it's cheaper to maintain this way. In theory! Not so much in practice.

Originally Posted by chaseav

So I called GM today. Not surprisingly, they had a mildly difficult time understanding what I was even asking for. The rep did not have the answer and admitted that but was helpful enough to call my local dealer for me. After about a 15 long phone call, the answer I received was:

According to the Parts Department Manager, the transmission temp warning light will come on at 270-280 degrees depending on a number of factors. (I could probably put quotes around that but truly I'm paraphrasing.)

I replied, "so that temperature would be considered the temperature at which I would start doing damage to my transmission."

The answer, "yes, that's what I interpret that to mean."

So there we have it folks!

-------------------------------------------------------------------------------------


I never trusted our Parts Manager any further than I could throw a potato chip.


Go by your owners manual and the dash board.

'Take-off's are optional, landings are mandatory"




Bob

[chaseav]

Originally Posted by RareStream

Once a transmission hits 270 pulling a trailer up a mountain damage is already done and thousands of miles are deducted from the usable life of said transmission.

I appreciate you weighing in RareStream; do you have any source for that info?

[RareStream]

Originally Posted by chaseav

I appreciate you weighing in RareStream; do you have any source for that info?

Well, besides personal experience, its all over the internet. Here's a sample:

"Most automatic transmissions are designed to operate at a maximum temperature of 200 degrees. For every 20 degrees you go above this limit, you risk cutting the expected lifespan of the transmission by a factor of two. To put that in a better perspective, by the time your transmission reaches 300 degrees its life span will be reduced to 1/32nd of what is considered normal. You should also note that at temperature as low as 240 degrees your organic oil based transmission fluid can turn to varnish, leaving it unable to properly lubricate the moving parts inside your transmission."

The Best Ways to Destroy Your Transmission | Mister Transmission

My personal experience was when I had an overheated engine condition due to the plastic stopcock on my radiator breaking, expelling all the coolant for the engine. There was no warning as on this vehicle because the coolant temperature sensor measured just that; the coolant, NOT the cylinder head temperature. So, with NO coolant, there was literally nothing to measure the temperature of, and the dash temperature gauge didn't bulge. By the time I heard pinging and pulled over, the head was toast. The engine got SEVERELY molten hot. Well, the transmission, which had NEVER had a problem previously, is of course bolted right to that molten hot engine, so of COURSE the transmission got hot. Well, about 3 weeks later going up a hill in Hurricane, Utah (not pulling anything) the transmission failed. The diagnoses was failure due to excessive heat...and the only time that transmission EVER got hot was when the engine overheated. It should be noted that about a month earlier I had the tranny's normal service done at a reputable Chrysler dealer including a complete replacement of all ATF+4 with an absolutely clean "like new" bill of health. The transmission failed for absolutely no other reason beside the fact that it got SEVERELY hot...and the heat was due to thermal transfer from the engine. That was a several thousand dollar lesson...and it was a normally bulletproof non-electronic Chrysler Torqueflight 3 speed. I can't imagine if it was a modern multiple speed electronically controlled tranny...there's no way it would have lasted the 3 weeks the old Torqueflight did...

Or, you can go ahead and believe that 270 degrees is safe for a modern electronic automatic transmission...once that point is hit, damage is DONE.

[jcl]

There is some very good information in the Duramax forum thread that cwf linked to just above. Thanks, cwf. The writer there was the chief fluid engineer for Allison, before and after GM's involvement. He was involved with Dexron fluids, and the newer synthetic fluids. He talks about safe transmission temperatures from a design engineer perspective, and as author of several transmission fluid specs.

One quote he had (in reference to an Allison 1000, which is used in the GMC 2500 diesel, and is a modern electronically controlled automatic) is that it will run all day long at 250F without any concerns to transmission or fluid degradation. At 325F fluid temperature on a 600 hour continuous test they didn't see much change. The internal transmission parts were designed to run up to 350C.

Just another data point, referencing modern transmissions and fluids, from someone who seems to know his stuff.

My own vehicle when equipped with a ZF automatic used a 270F alarm point before they turned on the additional cooling fan. They weren't worried about damage before that point, but they are using modern synthetic fluids. Very different than what the old three speeds used. The electronics actually help, as well, since they provide additional monitoring and protection.

Jeff

[ROBERT CROSS]

...."Or, you can go ahead and believe that 270 degrees is safe for a modern electronic automatic transmission...once that point is hit, damage is DONE."

Thank you, I will.
As stated, 270 is a safe LIMIT.

FWIW...if your transmission is empty, don't depend on the gauge, the reading is not accurate under those circumstances and it's very difficult to toe.


Boob

[chaseav]

RareStream mentions visiting the Chrysler dealership... maybe the Dodge products operate at lower max temps. Or maybe the temps are taken at different points. Trying to find a way we can all be correct. I did get a chuckle from this, "besides my personal experience, it's all over the Internet." Because if it's on the Internet, it must be true right?!? I've been on a lot of the blogs too trying to find out the info and it does sound like if it were to be put to a vote, most seem to say 250-270 is "about at hot as you should go" territory at least in a GM product.

Knowing the little I do about metallurgy, I'd find it very hard to believe that the life of components of a transmission would even be mildly affected by 200 degrees and even 300 degrees if not for prolonged or frequent occurrence.

[RareStream]

Originally Posted by ROBERT CROSS

...."Or, you can go ahead and believe that 270 degrees is safe for a modern electronic automatic transmission...once that point is hit, damage is DONE."

Thank you, I will.
As stated, 270 is a safe LIMIT.

FWIW...if your transmission is empty, don't depend on the gauge, the reading is not accurate under those circumstances and it's very difficult to toe.


Boob

No one stated ANYTHING regarding a situation where a "transmission is empty." Transmission fluid is not the same thing as engine coolant. Competent reading comprehension would be helpful here.

Also, the correct word to be used is "tow" and not "toe" as in "towing" a trailer. However, the distance a transmission can actually do that will be severely decreased by letting the tranny temperature ever hit 270 degrees (lol lol lol). A competent tow vehicle would be a better investment for adequate towing; i.e., one that can tow a trailer without overheating the transmission.

But, it's always amusing seeing someone pulled over on the side of the road trying to tow a big load up a hill because they didn't monitor their temperatures adequately until an alarm went off on the dash...that needle touching the red surely couldn't be anything to worry about pulling up that mountain. Nosireebob...

[RareStream]

Originally Posted by chaseav

I did get a chuckle from this, "besides my personal experience, it's all over the Internet." Because if it's on the Internet, it must be true right?!?

No one said that. Try paying attention. The internet is a vast resource; you have to have the competency to filter out improper information. As such, "safe" automatic transmission temperatures are easily researched, as are the effects of heat on different transmission fluids. And yes, the internet is a valuable resource for doing such. It's actually not rocket science. Excess heat=bad, no matter how you try to argue the fact.

Originally Posted by chaseav

Knowing the little I do about metallurgy, I'd find it very hard to believe that the life of components of a transmission would even be mildly affected by 200 degrees and even 300 degrees if not for prolonged or frequent occurrence.

I agree with your first point above. You apparently know little about metallurgy as you stated. If you think the components of a transmission are only made of metal, you are sadly mistaken and grossly misinformed. The damage is done to modules, seals, clutches, breakdown of fluid, etc...as well as "metallurgy" as you stated. Before you try to give others improper information regarding what's a safe temperature range for an automatic transmission to operate in, you should really have some sort of clue as to how an automatic transmission works and the parts contained therein. It's not just a mystery pump full of nothing but metal.

Regarding what you stated regarding "if it's on the internet it must be true," you have definitely proven your point that that is NOT the case.

[ROBERT CROSS]

Originally Posted by RareStream

No one stated ANYTHING regarding a situation where a "transmission is empty." Transmission fluid is not the same thing as engine coolant. Competent reading comprehension would be helpful here.

Also, the correct word to be used is "tow" and not "toe" as in "towing" a trailer. However, the distance a transmission can actually do that will be severely decreased by letting the tranny temperature ever hit 270 degrees (lol lol lol). A competent tow vehicle would be a better investment for adequate towing; i.e., one that can tow a trailer without overheating the transmission.

But, it's always amusing seeing someone pulled over on the side of the road trying to tow a big load up a hill because they didn't monitor their temperatures adequately until an alarm went off on the dash...that needle touching the red surely couldn't be anything to worry about pulling up that mountain. Nosireebob...

RS,

Reading comprehension...I'll give you reading comprehension.
What I if told you... I don't understand?
What I if told you….you can't read.


Your taking this way too seriously.
There is a definite banal lack of appreciation for the subtleties of the absurd around here lately.

And bie the way... I'll toe if I want too.

Bob

[CBWELL]

This is getting almost as much fun as "The Hitch Wars"!!! I wonder if the type of hitch on the toe vehicle has any input into the tranny temperature??? LOL

[SteveSueMac]

FYI - ProPridersen hitches keep your toe vehikle's tranny cool, work with under inflated tires, and make your CureEgg coffee taste better. They can balance your Centramatics offset on your axels and cure diseases from time travel in many countries. I know this from personal experience and countless stories I've read on the interwebs. So...there's that.

😃😁😙

C'mon people now - smile on your brother - everybody get together- time to love one another right now....

[chaseav]

I'll just recap: As the OP I was reaching out to others ON THE INTERNET about what first hand experience they might have towing their Airstream. The source of my information that I ended up posting was actually from the manufacturer of the vehicle. General Freaking Motors himself! I couldn't imagine a more definitive source... but anecdotes on the net... meh why not.

Robert Cross showed a picture of his temp gauge clearly showing a red arc and cited his experience (the aforementioned first hand experience I was seeking).

Others referenced their experience and one referenced a very insightful thread from a tech at Allison who did all the testing for a very long time on these transmissions who may or may not swear on a Bible that 325 was hot but not damaging.

Everyone was in general agreement that temps of 250+ would not do lasting damage to your (General Motors) transmission.

RareStream cites first hand but unrelated experience (and that of the Internets); the toasting of an engine and heat transfer damage to his transmission, then it fails after being given a clean bill of health by an expert and suggests 200 degrees is max.

It's too bad there isn't a way we could vote on their rather than having to use words to convey our thoughts. Cheers and good evening Gents.

[RareStream]

I think you should run your transmission at near 250+ on all climbs pulling your trailer for the next several thousand miles and report back to us with your results. With pictures...that makes it more fun!



(btw tranny temp of 325 "not damaging" heeheheeeheeheeehehheheeeheeeeehee)

[jcl]

Originally Posted by RareStream

(btw tranny temp of 325 "not damaging" heeheheeeheeheeehehheheeeheeeeehee)

If you take a look at the provided link, the guy who wrote the fluid spec gives some good insight. He was talking about the transmission there, not the fluid. He recommended you could run a modern synthetic transmission fluid all day long at 250F, at least in the GM transmissions he was involved in designing fluids for.

[jcl]

Originally Posted by RareStream

The internet is a vast resource; you have to have the competency to filter out improper information. As such, "safe" automatic transmission temperatures are easily researched, as are the effects of heat on different transmission fluids.

I have seen that chart of transmission life expectancy before, and in fact saw it many years ago. So I looked back to see what it actually referred to, the original source not having been provided.

The accompanying text states that it is for non synthetic ATF, and that the numbers would be different for synthetics. And it doesn't appear to have come from a transmission fluid supplier, but rather a vendor of aftermarket transmission coolers. Perhaps they have a vested interest?

Since Dexron III is no longer available and has been replaced by Dexron VI, which is fully synthetic, do you have a chart for a modern transmission fluid, whether Dexron VI or a ZF Lifeguard 6 or 8?

Jeff

[RareStream]

It's not just the transmission fluid that breaks down with heat, but the seals, modules, clutches, and gaskets.

Add to that excessive heat (325 degrees lol) the stress of pulling 8000lbs of trailer and the torque required to do that, and you're just begging for Good Sam to tow you to the nearest rip-off transmission shop in the middle of nowhere.

NO matter what anyone may try to use to contradict the obvious, excess heat WILL kill any automatic transmission regardless of how advanced the lubricant is.

Just has been true for the last 70 years of trailer towing, HEAT = BAD.

[jcl]

Originally Posted by RareStream

NO matter what anyone may try to use to contradict the obvious, excess heat WILL kill any automatic transmission regardless of how advanced the lubricant is.

Just has been true for the last 70 years of trailer towing, HEAT = BAD.

I don't think anybody has claimed otherwise. Excessive heat is bad. The discussion is around what defines excessive. Claiming that it is the same temperature as it was 70 years ago seems a stretch.

You got burned because of a bad repair. When they fixed the engine overheat, they should have changed the transmission fluid. Because they didn't, you failed a transmission three weeks later. If you had an electronically controlled transmission, like we have today, that wouldn't have happened because the transmission would rely on a dedicated fluid temperature sensor, and the fault would have been logged. And we know where the manufacturers set those alarms, whatever duty the transmission is under.