2011 Yukon XL Denali 6.2L cooling trouble while towing

[Mboulant]

I specifically purchased this vehicle because we have a 5000lb camping trailer and needed an adequate vehicle to tow and haul my family of 6. We previously had a 2008 Yukon XL with the 5.3L engine and it struggled to pull our trailer. I can feel the difference in power, but I still have trouble keeping the temp down around 210 when climbing hills. For those familiar with Southern Utah, I live in Las Vegas and climb from St. George up to Cedar City and then up near Brian Head. This is a significant climb, but I take it slow and really have to watch my speed to keep the temps down. Even with constant attention, the temp sits around 235 when climbing those hills. They do drop back down to 210 when I reach the top and begin to descend, but I wasn't expecting to have to pay this close attention with a vehicle that should tow my trailer with ease. I have installed a transmission fluid cooler and trailer brake controller, but everything else is stock. Is this normal or is there something I can do to improve the cooling system? I am mechanically inclined and can take on just about any repair, I just don't know what to do to make a significant improvement.

I have a trip planned to Southern California on Labor Day. I am worried about the climb between Primm and Baker, as well as the climb out of Barstow, up the Cajon Pass.

Thanks for any help,

Mike

 

[Matt_]

I'd consider regearing to 3.73s.

You could also see if someone makes a deeper trans pan with cooling fins.

 

[08grey]

What tranny cooler do you have?

 

[Mboulant]

What tranny cooler do you have?

Derale Series 8000 Plate-Fin Trans cooler

 

[Mboulant]

Since installing the transmission cooler, Trans temps maintain between 180-200 most of the time and only increase to around 205 when climbing. Ambient air temps are around 110 this weekend and Trans temps still within those levels. My concern is with coolant temps.

Thanks,

Mike

 

[Mboulant]

I'd consider regearing to 3.73s.

You could also see if someone makes a deeper trans pan with cooling fins.

Matt,

Gear ratios aren't something I'm that familiar with. It doesn't sound like something that is easily tackled. What benefit would changing to 3.73's have?

Thanks,

Mike

 

[Matt_]

Regearing gives mechanical advantage back to the drivetrain. It's a dual hatted improvement, lowers the torque required to move the load forward and also increases the RPMs necessary to maintain a given speed (in this case, keeping the engine closer to its peak power output when pulling up a steep grade).

It's not a bolt on type job by any means, but easily handled by any drivetrain shop. Would also require a tuner to regropram the computer for the new gear ratio.

 

[08grey]

Matt,

Gear ratios aren't something I'm that familiar with. It doesn't sound like something that is easily tackled. What benefit would changing to 3.73's have?

Thanks,

Mike

But isn't it awd? Can you change the gears on the rear on Awd?

 

[Matt_]

You have to change gears in both axles, just like any 4x4 truck.

 

[950410]

Is the transmission hunting for gears during the climb? Is the torque converter unlocking to make the pull? I would probably put the shifter in manual mode and hold the trans in 4th or 5th gear (if it's a 6-speed) and make sure the converter is staying locked. Constant shifting and an unlocked converter creates a lot of heat.

How long does this hill take the climb? Really I wouldn't worry too much about the trans temp rising on a hill, as that's common. As long as it's not rising excessively or stays that hot for too terribly long. Just my two cents.