Towing stability

[Geotrash]

I tow a #5000-ish boat with my 2008 Yukon XL and it does pretty well but I will have to say I think the 4 spd transmission is really the weak point, meaning, I think the 6 speed would work much better. I did add an aux cooler and on the hottest day, it stays at or below 200. Winter, well it doesn't warm up unless I drive quite a ways. I wonder if that will be a long term issue. I could really bypass the aux cooler in the winter. Any opinions?

As I understand it, the concern is really about getting any moisture that has accumulated in the fluid, out of the system. Hence GM's recommendation to set 150ºF as a minimum operating temperature. That said, I have never heard of internal corrosion being a problem on any transmission unless is was in a flood. And if you're driving it often, corrosion won't have a chance to take hold to any significant degree anyway. So I personally think the risk is low, but I don't have any data other than anecdotes to work with.

 

[Marky Dissod]

I tow a #5000-ish boat with my 2008 Yukon XL and it does pretty well, but I will have to say I think the 4L60E is really the weak point, meaning, I think the 6L80E would work much better.

It would do better with (a) 4.10 axle(s), which is relatively easy.
Making your vehicle properly utilize a 6L80E is not impossible, just much easier said than done.

I did add an aux cooler and on the hottest day, it stays at or below 200F.
Winter, well it doesn't warm up unless I drive quite a ways. I wonder if that will be a long term issue.
I could bypass the aux cooler in the winter. Any opinions?

You've no worries until the weather starts turning colder again.
When fall happens, try covering the external cooler. Block cool air from moving through it.
If the ATF temps get under 160F even with no air moving through the cooler, then bypass it.

 

[Airman68]

You've no worries until the weather starts turning colder again.
When fall happens, try covering the external cooler. Block cool air from moving through it.
If the ATF temps get under 160F even with no air moving through the cooler, then bypass it.

Thanks for the advise. I'll keep a closer eye on it and see where it is in the colder weather.

 

[Airman68]

It would do better with (a) 4.10 axle(s), which is relatively easy.
Making your vehicle properly utilize a 6L80E is not impossible, just much easier said than done.

Yeah, I would agree with the 4.10 axle. I guess sometimes you have to weigh out the better towing with the mileage for every day use. I tow almost every weekend from mid June to September. However the percentage of towing miles compared to other miles is low. I think before I would mechanically alter my truck, I would probably buy a newer version of it. Unfortunately, I just got most of the bugs worked out of mine so it might be a while. Well, and that money tree is not doing too well these days, LOL.

 

[Marky Dissod]

I think before I would mechanically alter my truck, I would probably buy a newer version of it.
Unfortunately, I just got most of the bugs worked out of mine so it might be a while.

Since your truck is in at least 'pretty good' condition, you'd likely be better off money-wise altering your truck -
especially if your alterations have a proven track record.
4.10 was an OE option for GMT900s, so it's not like you're venturing into experimental territory.

I would agree with 4.10. I guess sometimes you have to weigh out the better towing with the mileage for every day use.

This'll help:
1. I'm gonna tow/haul, or 'work hard'?
Y= 4.10 (at least) ... N=3.73 (at most)

2. I care more about city MpG, less about highway MpG?
Y=4.10 ... or ... N=3.73

3. Many or mostly steep &/or very long hills where I usually drive?
Y=4.10 ... or ... N=3.73

4. My tires are taller than OE?
Y=4.10 ... or ... N=3.73

 

[Airman68]

Those are all great points. Yeah, my truck is pretty good, probably above average for my area considering the stupid WI rust cancer on most vehicles up here. I never considered the tire issue. I do have one size bigger then OE so that could definitely be a factor. If I decided to go the swap route, are the axles specific to the Yukon or are they the same over the whole GMT lineup? Truck vs SUV and are they year specific?

 

[Marky Dissod]

I never considered the tire issue. I do have one size bigger then OE so that could definitely be a factor.

It IS a factor, regardless of what you mean by 'one size'.
Although the ring and pinion ratio remains constant regardless of tire size GOTTDAMNT!
using taller-than-OE tires effectively reduces the amount of power applied to the ground
and that's BEFORE accounting for the parasitic losses involved due to increased rotational mass/weight
nevermind the losses incurred by trying to push that power through more rubber
and don't forget increased aero drag.

If I decided to go the swap route, are the axles specific to the Yukon?
Or are they the same over the whole GMT lineup?
Truck vs SUV and are they year specific?

1. If it came in ANY GMT900, it should be able to work in any other, including yours, even if not instantly compatible.
2. Can't be sure, but I'd bet that the same applies to GMT800 axles as well.
If '2' turns out to be true, then that would even make GMT400 axles a possibility as well.
To make your life easier, you'd likely prefer an axle from a vehicle that came with a 4L60 or 4L60E.
But I'd also bet that an axle that worked with a 4L80E would be an effective upgrade, requiring a few OE-options changes.

 

[Airman68]

Thanks for the advice. I will definitely look into it. I got a sweet deal on a set of low mile 275/60/20 Wranglers and rims from a GMC truck. I have a stock suspension setup. They are just that much bigger that they barely rub at a full turn. They do look sweet compared to the stock rims and Bridgestone tires it had. I'll have to update my profile pic.

 

[Geotrash]

A towing stability thing happened to us today. We were pulling our camper down I-64 and drove through a monster gust of wind. It was so strong that I could feel the trailer start to wag behind me more than I ever have before, but before I could react the Yukon's trailer stability control kicked in and got the trailer squared away. It's a huge reason to have the factory brake controller.

 

[tagexpcom]

A towing stability thing happened to us today. We were pulling our camper down I-64 and drove through a monster gust of wind. It was so strong that I could feel the trailer start to wag behind me more than I ever have before, but before I could react the Yukon's trailer stability control kicked in and got the trailer squared away. It's a huge reason to have the factory brake controller.

Is there any stability response/support in a 2021 Yukon Denali when towing without the factory brake controller installed? I'm towing 5300lbs w/Curt after-market brake controller + WDH and interested in towing info in general.

I understand the vehicle can't apply trailer braking (doesn't know about them) with Curt but I thought I read something about vehicle wheel braking / stability assist that could help a bit with sway based on general vehicle stability sensors? or is that just misinformation....