transmission heating

[aeriqua]

Hi! We have a 2004 Suburban 3/4 ton with 3.73 axle, towing a 25' Excella. While we were towing it up to a ski resort at about 7000ft, a warning flashed on the dash about the transmission getting too hot. The manual says this warning should only show at over 265 degress and the gauge showed only 200 degrees. Does anyone know if this is a known problem? Should we only tow in 3rd, not in overdrive? If so, then why or when do we use the "tow" button to change how the transmission shifts while towing? Any ideas?

[Silvertwinkie]

I have the same truck, same year, only w/ 4.10s and I have not seen the "limp mode" warning you describe that I've read about in the book. Not sure if it had anything to do with the altitude, but I'd contact a Chevy dealer.

If you're towing up big hills, I'd be towing in 3rd or second depending on the grade hill/mountain and with tow/haul engaged.....

[vajeep]

We have the same 3/4 ton Burb, We tow a 27' Overlander 6060# fully loaded. I have never seen our trans temp go over 250 even in summer on long hills. I would let your dealer have a look. Sounds like a bad sensor...

What happened after the light came on??

[davidh]

If you were towing up a steep grade in overdrive that would explaine why TA Temp warning light came on, and if the gauge temp was at differant temp than what the warning light temp is suppose to be I would bring to dealer and have gauge replaced and complete check of system. Not all gauges are correct they can be off with there callibration's, was a heavy truck mechanic for 15 years found lots of bad gauges.

[Silvertwinkie]

Just for reference, our trans has never exceeded 200 degrees....yet.

[john hd]

Originally Posted by Silvertwinkie

I have the same truck, same year, only w/ 4.10s and I have not seen the "limp mode" warning you describe that I've read about in the book. Not sure if it had anything to do with the altitude, but I'd contact a Chevy dealer.

If you're towing up big hills, I'd be towing in 3rd or second depending on the grade hill/mountain and with tow/haul engaged.....

ditto on twinks suggestion.

hit the tow haul button whenever you have the trailer on.

since yours is a 3/4 ton you have the 4l80E tranny. you can tow in overdrive, if you were pulling a long grade it probably wasn't in O.D. if you were in rolling hills the advice to leave it in 3rd can have benefit, instead of shifting to 4 the trans will spin faster in 3rd pumping more oil and cooling faster on the down hills. you also get the added benefit of engine braking.

bottom line, take it to a dealer and have them check for software updates for the tranny and to check for any stored codes. i would bet if the trans hot light came on however briefly it would have left a code stored in the tranny ecm.

let us know what you find, i have the same tranny in my silverado and have had 60K trouble free miles. i have had my tranny over 200, but that was towing in 100+ heat at 75 mph. no warning lights.

john

[aeriqua]

thanks for the suggestions - we'll get it checked out at the dealer...and use 3rd

btw...we slowed down after getting the warning, and the warning "left"

[Tinsel Loaf]

Use a synthetic transmission fluid if your dealer drains the pan and converter. Synthetic fluid can take more heat before breaking down.

[Silvertwinkie]

I agree, the synthetic fluid will take far more than the trans can take. Problem is, if he really did hit 265 degrees, the trans fluid, if synthetic, would have taken the beating, but the bands, and clutches would have most likley started to warp, if he did in fact hit 265.

[vajeep]

Originally Posted by aeriqua

thanks for the suggestions - we'll get it checked out at the dealer...and use 3rd

btw...we slowed down after getting the warning, and the warning "left"

Just wanted to check in. What did the dealer find??

[aeriqua]

thanks for asking - we haven't taken the 'Burb in yet, and have had no symptoms with regular driving, no towing. Will report in as soon as we check it out. Thanks for all the suggestions

[aeriqua]

just to let you all know - we went all across the US to NY and back with no transmission warnings, even over the Sierras, Rockys, Bighorn Mtns. So we'll save some $$ for now, and hold off on the Dealer visit....

[hookedonclassic]

Just returned from 1150 mile trip to Colorado Rockies and across Nebr in 110 degree heat. Trans temp never exceeded 200 and engine 210 degrees. D/A. Loved the Allison in the mountains especially going down the mountains.

[2airishuman]

Originally Posted by aeriqua

just to let you all know - we went all across the US to NY and back with no transmission warnings, even over the Sierras, Rockys, Bighorn Mtns. So we'll save some $$ for now, and hold off on the Dealer visit....

hi aeriqua...

thanks for the update...people should do this more often.
are you out of warranty? isn't this visit covered?

while i agree it may have been a false positive code...
i'd still want it checked. they can run the diagnostics
and find all the alarm codes...errors or otherwise.

the overall tranny fluid temps may not rise much...
while the 'local' temps are very high...
so going by factory gauge temps isn't wise...
because by the time they read high....
it's really really high.

also how are the gauges calibrated?
on the ford...they are very imprecise...
stock gauges often have 'temp ranges'...before the needle moves much.
my oil temp gauge goes immediately to the mid point with ignition...
that's how it's calibrated...so from cold to warm it does not move...

i'd still want to know the codes thrown...

cheers
2air'

[CanoeStream]

Congrats Rich! You make me look forward to stretching my D/A!!

[scottanlily]

The code should be stored in the PCM memory .I would go to a good
trusted mechanic and he can pull the code with his scan tool .It does not need to be a dealer ,unless its warranty stuff, nor a transmission shop.
The trans probably was hot ,but It should not be in overdrive except on the flat roads ,no grades ,put it in 3rd.The 4L80E is a stout trans ,but heat will
kill an automatic trans .you have the 3:73 ratio so even more reason to not
use overdrive on any grade .Pull the trans dip stick and smell the fluid ,it
will have a burnt smell if it got toasted ,and the fluid will not be nice and red
more orangish in color.No mistaking that burnt fluid smell ,even for a non mechanical person.The allison 5 speed is a extremely heavy duty transmission
,but must also be cared for as well.

Scott