245 degree transmission oil on long steep grades

[ashe]

I have a 2009 Yukon XL Denalli and have had heating concerns out west on some of the long steep hills in Utah, Colorado, Wyoming, Montana. Pulling a 5000# ac trailer temps would reach 245 degrees using Tow Haul mode or shifting manually to control down shifting.
Now have a larger 28 footer that could weigh 8000+ lbs loaded. Brochure says 7900lbs maximum towing capacity.
Question is have you experienced a similar problem or heard of anyone who has...thinking about changing the rear end to a 3.73 or getting a bigger oil cooler if not both in hoping to solve capacity and tranny oil heat issues. Or buy a 3/4 ton Yukon XL. I drove one and the 6.0 engine seems week compared to the 6.2. Hate to do that if not necessary.

[dznf0g]

That's a little high, IMO. You'll definitely need a 3.73 and an additional cooler. Even then you're still overloaded. The 3/4 ton is probably the way to go....with a 3.73.

[TRfour]

Hi ashe, there is some great info that should help you out in the link below.

Actual transmission oil temperatures can vary, depending on where the temp sensor is installed in your particular application. Your owners manual may have an maximum transmission oil temperature for extreme Towing conditions, as you have mentioned.

A must read; Automatic Transmission Cooling | OldIHC

Good luck, and I hope this helps.

[4RXLA]

I had a 2008 Tahoe with the 5.3 vortec and a 3.73 and 8000lb tow rating and it would run hot towing a 6000lb SOB on long climbs. You will be better with a 3/4 ton.

[Streamside]

Originally Posted by ashe

I have a 2009 Yukon XL Denalli and have had heating concerns out west on some of the long steep hills in Utah, Colorado, Wyoming, Montana. Pulling a 5000# ac trailer temps would reach 245 degrees using Tow Haul mode or shifting manually to control down shifting.
Now have a larger 28 footer that could weigh 8000+ lbs loaded. Brochure says 7900lbs maximum towing capacity.
Question is have you experienced a similar problem or heard of anyone who has...thinking about changing the rear end to a 3.73 or getting a bigger oil cooler if not both in hoping to solve capacity and tranny oil heat issues. Or buy a 3/4 ton Yukon XL. I drove one and the 6.0 engine seems week compared to the 6.2. Hate to do that if not necessary.

Do you have the tow package with the external transmission cooler?

[barts]

Your transmission will not last long at 240F; wear accelerates very quickly past 220F. I fitted a large cooler to replace the small one on our diesel; this has made our transmission temps rarely exceed 200F, even dealing with 10% grades that are miles long. If my roadspeed drops to 25 mph or below due to off road conditions, we're down in 4low w/ the front hubs unlocked to let the transmission get into 3rd where it will lock.

Make sure to use a cooler w/ a thermostatic bypass so that transmission will warm up in winter time.

I'd also get a bigger tow vehicle if you're already past the max weight...

- Bart

[Jammer]

I think this is an example of the sort of thing you can run into towing heavy trailers with a 1/2 ton. I'm not sure it's entirely a cooling problem, the 4L60e just isn't designed for that kind of sustained load.

There are some choices if you want to add more cooling. Aftermarket transmission coolers are one. You might also pick up some cooling from a Mag-Hytec aluminum pan, which would also add some oil capacity that might help a little.

[TRfour]

GM recommends that the maximum transmission-fluid temperature (measured in the sump) for short durations shall be no greater than 285 degrees F. At 300 degrees F, research shows, metal parts inside the transmission begin to warp and distort, seals begin to melt, and fluid life is extremely short because of heavy oxidation.

[TRfour]

I would strongly recommend using synthetic lubricants, engine, transmission, on and on! They protect much better in normal and extreme conditions, even when not towing!!
Automatic transmission fluid - Wikipedia, the free encyclopedia

[Andrew T]

I am pretty sure the 1/2 & 3/4 ton Suburbans with 6.0 or 6.2 Litre motors use the same transmission so you have nothing to gain from a 3/4 except a slightly larger factory cooler. Because you have a 6 speed transmission you have little to gain with a 3.73:1 axle ratio.

I am sure you have an external cooler but do confirm it is there to be sure. You could also have a inacurate gauge. What RPM and speed are you climbing at? It may just be a matter of dropping a gear and easing up on the speed a little.

Andrew T

[ashe]

Wow, I just want to say how much I appreciate the input and experienced shared on my question so far. Very helpful and keep em coming.
Nick

[ROBERT CROSS]

Originally Posted by ashe

Wow, I just want to say how much I appreciate the input and experienced shared on my question so far. Very helpful and keep em coming.
Nick

POI....The PCM will go into "limp mode" if the trans temp exceeds the 280 degree threshold.
Working at a Chevy store I never pulled that fault code when scanning.

Bob

[Pahaska]

Thank goodness for my Allison that never rises more than about 10 degrees from where it is apparently thermostatically controlled, regardless of outside temperature or grade. Most of the time, the temperature never varies.

[dznf0g]

Originally Posted by Andrew T

I am pretty sure the 1/2 & 3/4 ton Suburbans with 6.0 or 6.2 Litre motors use the same transmission so you have nothing to gain from a 3/4 except a slightly larger factory cooler. Because you have a 6 speed transmission you have little to gain with a 3.73:1 axle ratio.

I am sure you have an external cooler but do confirm it is there to be sure. You could also have a inacurate gauge. What RPM and speed are you climbing at? It may just be a matter of dropping a gear and easing up on the speed a little.

Andrew T

IIRC, no 6 speed in '09. While the 6.2 and 6.0 use the same trans DESIGNATION, the 6.0 may have internal differences, because it is designed for higher loads. All GM vehicles with a 6.2 ALUMINUM block will have lower tow and load ratings than the CAST IRON 6.0. Since the tow and load ratings are lower on the 6.2, I suspect the trans coolers/radiator, etc. are not as high capacity as the 6.0. EVEN THOUGH the 6.2 is capable of higher HP and higher torque, the torque load capability is not as great with the 6.2 as with the 6.0, and could cause accellerated wear over time. 6.2 was designed as a "luxury" V8, not a work horse, like the 6.0.

The reason there are no 6.2's in 3/4 ton and up, is due to the fact that an aluminum block will "twist" at very high torque loads. thus, the lower ratings and PROBABLY not the same ancillary equipment.

[redwoodguy]

I wonder if I have a transmission cooler? Is it easy to see? Where is it usually located? I have a 2007 Suburban 4WD.
So far 150F is the highest I have seen my gauge read.

[ROBERT CROSS]

Originally Posted by redwoodguy

I wonder if I have a transmission cooler? Is it easy to see? Where is it usually located? I have a 2007 Suburban 4WD.
So far 150F is the highest I have seen my gauge read.

Yes...it will have an up-graded cooler with the towing package. KNP option code listed on the sticker on the inside of the glove box door.

Bob

[ashe]

I do have a 6 speed transmission in Denalli package. Your comments are appreciated and insightful Andy. I know your well versed in hitch approaches. Is their a place I can confirm the transmissions between 1/2 and 3/4 ton vehicles for GM. Yesterday a transmission shop told me to add supplemental air bags and larger oil cooler to solve my towing capacity and tranny heating problems. Anyone have any experience with that solution? Frankly, I am worried about what a 3/4 ton truck will do to my 23 ft smaller airstream will I tow as I have been told the stiffer suspension will transfer all the road vibrations into the trailer and cause interior problems with the stress.

[dkottum]

". . . as I have been told the stiffer suspension will transfer all the road vibrations into the trailer and cause interior problems with the stress."

That is also indicated in your Airstream Owner's Manual, but there is a few on this forum that, based on their scientific experimentation and reasoning, you can ignore it.

You'll hear from them shortly.

doug k

[Alumaholic]

Suburbans and Yukons changed significantly with the 2009 model year.
I found this out the hard way, I bought one.
This is my fourth 'Burban, a 1500, and it is built for luxurious road trips but not towing.
> Gone is the 3:73 differential replaced by something much higher.
> The 6 speed tranny puts a higher gear at the top end where it doesn't contribute to towing.

I can barely tow my utility trailers and certainly not my Airstream.
The transmission would be in 3d or 4th gear all the time and would soon cook itself.
That's why I bought the 2500HD Duramax with 6 Speed Allison

[ROBERT CROSS]

ashe

Be careful on the air-bag suspension "up-grade".

This is the correspondence I had regarding the Firestone system.


On Sep 7, 2011, at 12:34 PM, INFO @ SuspensionConnection wrote:

The Firestone air bags will increase your weight carrying capacity by
5000 pounds. I definitely recommend this system for your Burb:
Chevy Firestone Air Bags - 2000-2009 Chevy Suburban 2500 4x4 & 2wd - Firestone "Ride-Rite" Air Bag Helper Springs (Rear) by Firestone # 2253

Thanks

-----Original Message-----
From: Robert Crosse [mailto.......,,,,,..........com]
Sent: Sunday, September 04, 2011 10:59 AM
To: info@suspensionconnection.com
Subject: Airbag Chev Suburban

I am wondering how much more payload I will gain by adding rear bags to
my 06 3/4 Burb. Not sure of what the "level load capacity" of the Burb
is now.
I am concerned about overloading the axle as I tow an RV. How much would
I gain by upgrading the suspension with a quality air bag system.
Look forward to your recommendations.

Thank You,
Bob

Notice that the "exspurt" stated I could increase my payload too 10500lbs on a rear axle rated at 5500lbs.

Airbags will NOT increase the payload capacity, that is determined by the rating of the axle itself. They will only level the vehicle when loaded.....hence the vague term, "level load capacity". Still not sure exactly what that means.

Look at the driver door jam sticker for that rating.

Aux tranny cooler, never a bad idea. Installed aux cooler/filter on our 95 Burb, very good addition, the added capacity dropped op-temp several degrees.

Bob