2005 Yukon XL Denali tranny whine while towing/braking?

Hi all. Yesterday I gave my 2005 Yukon XL Denali a pretty heavy tow test, and it maybe failed a little but maybe not? I'm trying to figure out if anyone else experiences this with their GMC trucks with the 6.0L or other Denali (AWD) systems.

Trailer: 2017 Jayco Jay Flight - dual Axle 5000lbs dry, I was probably at about 5500lbs yesterday.
Tow Vehicle: 2005 GMC Yukon XL Denali 6.0L AWD - 158,000 miles.
Recurve R3 weight distribution/anti sway.

Tow Route: Started at 4900ft elevation, drove i-70 in Colorado to Silverthorne from the front range. It's a 6-7% grade off and on, reaching 12,000ft I believe at the highest point then dropping down the "ike gauntlet". (93 miles)

The trailer tracked wonderfully, I had no issues controlling it on the way there and I used tow/haul mode the entire trip. The Yukon didn't sound much different than it ever does other than higher RPM, it ran fine and I was able to go about 50mph even up to the top of the gauntlet which isn't bad at all for power, I got about 11.4 MPG average over the entire trip. My issue comes with the transmission noise.

At about 30-45 minutes in to the trip, I had been climbing for a while and we went over the crest of a hill. I lightly tapped the brakes and heard a really weird whining noise, sounded almost like a power steering whine. This only happened when I would brake, the noise came from the front of the vehicle and at first I thought it was ABS/Brake master or something like that....but it wasn't. It progressively got worse, then the transmission would make the same sort of whine any time I used it to engine brake. I believe it was likely due to the amount of stress that is put on it pulling up grade, but it never slipped/clunked etc.

Max transmission temp on the gauge was probably around 230-240 at the worst, as I descended it would drop back down to 180-200.

The noise seemed to have a direct correlation with the temp, any time it was about 215 or higher it would whine more, and whine while braking (weird).

Long story short, I made it home, drove about 300 miles total with trailer and the Yukon seems fine, the transmission doesn't really whine while disconnected from the trailer, it feels normal as it has in the past, but I imagine it's just not good for it.

My gut feeling is that it's just too hard on the AWD system. At first I was a little stumped why it would whine/cause noise while braking but it makes sense because the front drivelines are never disengaged in the Denali. When braking, I'm also applying pressure to the transfer case which wouldn't occur in a non AWD system, at least with the front brakes.

I really like the way it towed but I'm pretty concerned that if I do this over and over, eventually (probably sooner rather than later), the transmission or transfer case is going to fail. I would really prefer a selectable 2wd/4wd rig to tow, my options are limited though (need to seat 6 people). I'm thinking about looking at either a Nissan Armada, Toyota Sequoia, or Ford Expedition EL with 3.5 EB.

I would love to hear if anyone has the same drive system I have and experienced the same thing...or even if you have a non AWD with similar noise?

Tow Vehicles

falconbrother
Explorer II
Jul 05, 2017
Personally, if it wasn't going to leave me stranded I would just take it easy and drive it. If it needs an overhaul then I would get that done. I have noticed that my 4L60e will have an almost imperceptible whine when it's been towing and working hard. I change the fluid and it's in good shape, no slipping, no shift issues, etc.. I don't think there's anything wrong with mine. It is what it is and I'll deal with it if it breaks. I don't think it will and I'm hyper aware of anything that seems out of sorts. Truth is nothing is certain in life.
jlrosine
Explorer
Jul 03, 2017
Hi guys, I have another towing update and figured I'd get your thoughts on the results.

I towed the camper again but this time I went up highway 285 in Colorado. It's still steep but not nearly as long and drawn out as i-70 here. It was a bout a 2hr drive and ended up stopping around 10,000ft.

Result:
I experienced the whine again but it was quieter this time, and didn't last as long. After I got to less grade/more flats with hills, it generally goes away slowly.

On the way home last night, I was heading from 10,000ft elevation down to about 5,000ft. I payed close attention to the temp gauge for the tranny and it never got above 180-190. The outside temp ranged from 45 degress to a max of about 65 as I got down in elevation, however I did start to hear the same "whine" sound coming alive after I was using the gears to hold down a 5-7% grade.

Given that the transmission wasn't hot, or wasn't nearly as hot as previous runs, I'm now wondering if it's my transfer case making the noise and not necessarily the transmission?

I generally start to notice the whining noise when I touch the brakes, the noise only comes from the front and it seems that it's due to the braking stopping the wheels....which are connected in the AWD to the case...then the tranny.

Temp wise it doesn't seem like it was nearly as hard on the transmission to use it to brake down the pass, but I'm sure it was equally as hard on the transfer case/diff as going up hill.

Any thoughts or speculation/recommendations?
carringb
Explorer
Jun 29, 2017
jlrosine wrote:
Another question. Do you think I damaged my transmission with the trip yesterday, and being fairly hot for most of the trip?

Possibly you shortened the life of some components. But if its still running and nothing is leaking, I would not hesitate to drive it.

My dad did something similar a couple years ago. My brother's driveway is about a 30% slope, with turn towards the top when you approach the house. He couldn't get the boat lined up, but gave it his best. About 15 minutes of repeated attempts (after a hard pull on the highway, on a 90+ degree day), it ended up puking a couple quarts of fluid out the vent, then was making a whine after it cooled down.

We did a full fluid swap the next weekend which made the whine go away, and the transmission is still working. That was 4 years ago.
jlrosine
Explorer
Jun 29, 2017
Another question. Do you think I damaged my transmission with the trip yesterday, and being fairly hot for most of the trip?
carringb
Explorer
Jun 29, 2017
I run the Tru-Cool Max 40k as well. It became necessary after my grill guard changed the airflow into the stock cooler.

441,000 miles on my transmission, zero work done to it, besides a couple filter changes early on. Now that I have the tru-cool max, and a Magnefine filter, I simply use the "Bucket Method" to do a full fluid swap every 100,000 and change the Magnefine. Last time my pan was dropped was at ~170,000 miles.
akcooper9
Explorer
Jun 29, 2017
jlrosine wrote:
@akcooper9 - What vehicle do you tow with? Those temps are crazy low :)

In the photo above, I had (sold to Dad) a 2002 Silverado 2500HD 6.0 / 4l80E combo that I installed the tru cool 40K unit on.

I also have a Yukon XL 2500 6.0 / 4l80E combo that we use weekly to tow the boat to the lake. I ditched the stock cooler for this setup (Tru Cool M7B)

This setup works much better then stock but temps will rise at idle or longer pulls but most of the time it sees 160ish.

Having done both, for heavy towing the tru cool is the only way to go
jlrosine
Explorer
Jun 29, 2017
@akcooper9 - What vehicle do you tow with? Those temps are crazy low :)
akcooper9
Explorer
Jun 29, 2017
jlrosine wrote:

The stock transmission cooler is fairly large, not much smaller than the one sent in the link above however I'm sure the tru cool does a better job, it looks a little thicker anyway, I'd be surprised if a new slightly larger cooler makes a 30 degree swing on temps, but I could be wrong.

I know I said that the whine gets louder with temp, however it doesn't really go away when the temps are in completely normal operating range. 180 - 200 degrees for a transmission isn't crazy hot IMO, and especially not when towing.

The tru cool cooler is much larger. It will very much lower temps 30+ degrees AND keep them there. I towed my 8K toy hauler through the mountains during the summer and never saw 180 degrees. Avg temp was 165
jlrosine
Explorer
Jun 29, 2017
I should have noted this:

The Yukon has been very well maintained at a local GMC Dealership. Every 30k miles up until about 120k the transmission fluid/transfer case/diffs were flushed, so it's definitely not a situation where it was neglected.

The tranny fluid is bright red, looks brand new, and there's not even a hint of brown really.

The stock transmission cooler is fairly large, not much smaller than the one sent in the link above however I'm sure the tru cool does a better job, it looks a little thicker anyway, I'd be surprised if a new slightly larger cooler makes a 30 degree swing on temps, but I could be wrong. There's only so much fluid running through the cooler at any given time and it takes a while to cycle it through.

I know I said that the whine gets louder with temp, however it doesn't really go away when the temps are in completely normal operating range. 180 - 200 degrees for a transmission isn't crazy hot IMO, and especially not when towing.

@APT - Yeah the main reason I was looking at the ecoboost, or an old Excursion was because of the turbos and the elevation I tow at. We plan to do a lot of Colorado camping because we live here and it's "easy"...easy until we have to go up passes and back down them with a trailer. For resale and longevity I'm not sure how the Ecoboost will hold up, I haven't seen a long enough track record to tell how durable they will be. I think the next best towing SUV would probably be the Toyota with the 5.7, I've owned a Tundra previously and I know that engine/transmission are up to the task, I just need to also haul 4 kids and a wife :).
mkirsch
Nomad II
Jun 29, 2017
The truck is 12 years old and has a significant amount of mileage on it. It's not inconceivable that the transmission might need some help just from normal wear and tear, and the extra stress of this rather light tow might be bringing it to light.