Our new 2015 GMC Sierra Denali Duramax 2500HD

[JBinKC]

I'm interested in how the Allison tow haul mode works with the Duramax engine brake on the 2015s. Steep grades with my older 2500HD Duramax in the tow haul mode are a pleasure, hardly requiring any braking at all. The Duramax runs so much cooler in the tow haul mode, and the Allison won't let the engine over-rev. I'm wondering if manual applications of the engine brake might cause over-revs and less controlled stops than slowing down with the big disc brakes and the automatic Allison downshifts in the tow haul mode. Just curious. My five-year old 2500HD Duramax with 60,000 miles is such a great rig, I've been immune to new truck fever up to this point.

[ghaynes755]

I don't think I have used the tow haul mode at all in mountains of the west. Use the exhaust brake any time I'm driving on the highway, better for any braking situation. But just have seen the néed with the FC25 I had for tow haul. Will try it when I get the Classic.

[Ed Brownfield]

I loved reading about your purchase and envy you for making a decision to move forward with the 2500 Denali diesel. I am having a terrible time trying to decide on which truck to buy and I usually don't have a problem making decisions!

We are new AS owners; picked up our 2015 28 ft. FC in August. I originally thought that we would be fine towing the trailer with my Infiniti QX 56 (towing capacity of 8,900 Lbs). We also bought a Hensley Hitch for weight distribution and sway control (safety is a big issue). We have towed the trailer about 4,000 miles now and we are not comfortable towing this size trailer with our SUV. We began looking at trucks and I have not been able to make a decision on which way to go. This is not normal for me I usually study a problem gather information and then make a decision. Not so with this decision, it is a really tough with no clear right answer. We want to use whatever truck we purchase as a "daily drive around" vehicle replacing my Infiniti QX 56 so a comfortable ride is important. We like the 1500 GMC Denali but the 1500 does not have the towing capacity of a 2500. The size of the 1500 and its maneuverability are appealing but not the towing capacity. The 2500 has the tow capacity but it is large and from what I have been told it is cumbersome for driving around town on a daily basis. Then factor in the decision of whether to buy a large gasoline engine or a diesel engine it all makes my head spin. I can not seem to find a good answer to my dilemma. Safety towing is a very important factor, and being able to stop quickly and maneuver quickly if need be are important. I would love to hear other seasoned AS owners thoughts and suggestions on what to do. I don't want to make a costly mistake!

[lsbrodsky]

Another Pandora's Box opened!!! There must be a quadrillion threads on tow vehicles.....all of the opinions are already here somewhere.
Larry

[gandttimes]

I believe the 1500 Denali with the 6.2 and 8 speed has a towing capacity of 12000lb and up to 7600lb gvw Plenty for your 28ft.
Sorry to change the subject a bit.
Probably if you are going to use whatever truck you buy as a daily driver, then pick all the trucks that will comfortably haul your trailer and drive them as you would drive a daily driver???


George

[greenflag]

Good questions Ed. Let me give some background on my experiences with tow vehicles. I towed SOB's with my old chevy 3/4 ton for years. In 2004 I bought a new GMC Sierra 1500 for a lot of the same reasons (better ride etc). I found it to be "adequete" for towing my 2007 25' AI. I wasn't completely satisfied though with the stability of the overall package. The short bed GM trucks also had a 26 gallon tank. In 2008 I decided to step up to Duramax 2500 crew cab long bed. I have never been sorry. The Duramax pulled my 25' AI like it wasn't there. The extra stability when passed by 18 wheelers was comforting. In 2014 I purchased a new 30' AI. There is no way in my opinion that the 1500 is suitable for towing a 30' AI with a gross of 8800 pounds.
I use my Duramax as a daily driver around town. I leave our sedan for the wife. The truck is hard to park, so pick your spot. Park further out and walk. Something we all probably need to do. I avoid parking structers when possible. If I have to, I just go to the roof and select a spot I can pull straight into and back straight out. I have not felt like these minor modifications to my routine are an inconvenience.
I plan to step up to a 2016 TV this fall. Some of my friends have Fords. I like them equally as well as my Duramax. Both have their pluses.
I am currently shopping for mudflaps to keep the road dings down on my Airstream. I read in a post that the Rock Tamers came with a flyer that said not to use them with Duramax TV's. Apparently not enough clearance between the exhaust and the mudflap causing heat damage to the Rock Tamer. I use a Reese Straight Line hitch. The Pro Pride may provide the necessary clearance.

[TinShack]

Originally Posted by time2play

Steve-what a beautiful truck! Very nice. You did good too. We've already put 500 miles on our truck, so we're ready to go. I'm curious how long before you get your tow mirrors. Our dealer spent days trying to find us a truck with tow mirrors. He finally found one in Yakima, then we had to wait another few days while he sent someone to go fetch it. I got the impression tow mirrors were very much in demand at that time.

Yolanda

Yolanda, Thanks! Besides the initial 500 mile break-in, there is a 500 mile towing break period too once you start towing. It's described in the manual on page 9-67.

I don't know how long it will be before I can get the mirrors installed. At this point if installed, all of the power components would work except for the amber lights on the back. GM is working on fabricating a a standard-to-tow mirror electrical connection to do this. According to my dealer there is a very high demand for the tow mirrors like you said, so they are confident it will happen quickly. They have two other people waiting for this as well. In the meantime, I bought a $50 pair of tow mirrors to use, I'll sell those on Ebay when the other mirrors are installed.

[KJRitchie]

Does it come with an integrated trailer brke controller? Is your wheel base 154"? The Ford F-150 Supercrew with 6ft bed is 157" so the GMC shouldn't be any more difficult to park. Is the exhaust brake an option on the diesel?

Just looking on Cars.com and there is a preowned 2013 Denali with color coordinated color camper shell, tow mirrors and step bars. 40k miles Has there been any major changes since 2013?

Kelvin

[Nurvet]

Nice truck!!! I have replied to your Classified ad on the hitch - is the hitch still available? Live in Puyallup, so close by.

[time2play]

Nurvet, yes the hitch is still available. I didn't get your response to the ad, not sure what happened.

Anyway, I just sent you a private message here on the forums.

[justretired]

you picked a real nice truck. They didn't offer a denali 2500 in 2009, that would have been my first choice. The rock tamers do get warm if you go that way. The nav system is nice but You can't use it while driving the truck, we use a second system to navigate . You won't regret this purchase.

[Sav'h Steve]

Originally Posted by Ed Brownfield

I loved reading about your purchase and envy you for making a decision to move forward with the 2500 Denali diesel. I am having a terrible time trying to decide on which truck to buy and I usually don't have a problem making decisions!

.snip..... and we are not comfortable towing this size trailer with our SUV. We began looking at trucks and I have not been able to make a decision on which way to go. This is not normal for me I usually study a problem gather information and then make a decision. Not so with this decision, it is a really tough with no clear right answer. ...(snip)... I don't want to make a costly mistake!

As has been said, this topic has lot of opinions and no real answers. I have an older F250 Diesel and it does an excellent job hauling...
But as a go to the store vehicle.... even with a shorter bed it's difficult to pull into shopping center parking lots (and get back out when you leave..).

My F250 just gets driven to keep the tires and batteries functioning as we have more vehicles than people.

When I replace I've been toying with a large gas 2500 Ram or GMC. I don't feel sitting is good for any truck -- including the diesel. Short runs doesn't even warm the engine block. Thus the gas seems better for me with intermittent use.

I personally have reservations about the Eco versions small block gas lasting 10 years without problems. I hear it screams (high RPMs) up moderate grades. Large Disp. Gas would rev too, but nothing beats displacement....

And the winner should be.......??

[ghaynes755]

George the 1500 ranges from 12,000 lbs (2 WD) to a low of 9,100# (Denali 4WD Std Box). As I was getting an oil change yesterday I was looking at the wall chart on towing. Lots of combinations depending on the vehicle, engine, 2/4WD, dually and the list goes on. The 2015 GMC towing brochure, and every manufacturer has one, runs 20 pages as a PDF.

What caught my eye was thinking about the 2015 Classic with a 10,000 max weight. Lots of posts here on the forum have folks towing something similar and when you look at the charts they could easily be exceeding the vehicle limits depending on the combination of parts.

If I still had my 2015 5.3L Gas Sierra 1500 by the numbers I was limited to 9,100 (they didn't have the max trailer when I got mine). Max trailer would take that to 11,000#. Duramax is 13,000#. These weights are using a WD hitch.

As to size other than low parking garages and a bit more maneuvering sometimes while parking I don't find the 2500 much worse than the 1500. Turning radius is larger and the truck with the same box (std) is the same length in 1500 or 2500. You can get a short box and shave off 15 inches. My 1500 was the short box and was a bit easier to maneuver but the standard box is much more functional with the extra length.

[ghaynes755]

T2P if you are an iPhone user get the GM Onstar app and you can do programming of the nav from your phone. Voice command on the phone works great.

I buy DEF at Walmart. That seems to be about the cheapest in the 2.5gal size. I've not looked at the DEF pump nozzle in the truck stops but the opening on the Duramax would probably not be sufficient to handle the fill rate. Maybe with a funnel or saving a couple of the 2.5 gallon cartons. They work great since they supply a short plastic hose.

[ghaynes755]

Photos of my RockTamers mount on the ProPride stinger and the front and back Duraflaps mounted. The silver is an option.

[gandttimes]

Originally Posted by ghaynes755

George the 1500 ranges from 12,000 lbs (2 WD) to a low of 9,100# (Denali 4WD Std Box). As I was getting an oil change yesterday I was looking at the wall chart on towing. Lots of combinations depending on the vehicle, engine, 2/4WD, dually and the list goes on. The 2015 GMC towing brochure, and every manufacturer has one, runs 20 pages as a PDF.

What caught my eye was thinking about the 2015 Classic with a 10,000 max weight. Lots of posts here on the forum have folks towing something similar and when you look at the charts they could easily be exceeding the vehicle limits depending on the combination of parts.

If I still had my 2015 5.3L Gas Sierra 1500 by the numbers I was limited to 9,100 (they didn't have the max trailer when I got mine). Max trailer would take that to 11,000#. Duramax is 13,000#. These weights are using a WD hitch.

As to size other than low parking garages and a bit more maneuvering sometimes while parking I don't find the 2500 much worse than the 1500. Turning radius is larger and the truck with the same box (std) is the same length in 1500 or 2500. You can get a short box and shave off 15 inches. My 1500 was the short box and was a bit easier to maneuver but the standard box is much more functional with the extra length.

I see that there is a difference in the builds from the US to Canada. We don't have the Denali 4x2 only 4x4 and as far as I can see you can't order the max tow package on the 1500 Denali so you can only get 3.23 axle
A Canadian build Denali with 3.42 gives it's tow capacity of 11700 lbs. Also on the SLT with 6.2 and max tow we can build it with 7600 lb GVW, whereas you can't?
Strange.


George

[Drathaar]

Very nice truck! I thought long and hard about getting one, too.

We upgraded to a 2014 F350 w/Powerstroke. I believe the tow haul mode is similar to the GMC in that it uses a combination of transmission and exhaust braking. Coming from a 2000 F250 diesel, there's a light year or two of improvement. When it came down to it, the tipping point for the Ford was my trust in the service department of my dealer.

[warbler5]

In 2011, we upgraded from our 2002 GMC Yukon XL (which we loved) to a 2011 GMC Sierra Denali Duramax 3500 HD to tow our 2004 30' Classic. The longer wheel base of the truck fits better with the 30' Classic. There are so many great things about this vehicle....double the fuel economy, the downhill braking feature, the mirrors, the back-up camera....well, you know! My husband got every option available on our vehicle....except the snow plow package! I only asked for 5 things: no duallies on the rear axel, the 6-foot bed, input on the color, no decals (advertising your 4x option), and 4WD with posi-traction. It has been a wonderful tow vehicle!

[Lara Me]

Originally Posted by ghaynes755

I've not looked at the DEF pump nozzle in the truck stops but the opening on the Duramax would probably not be sufficient to handle the fill rate. Maybe with a funnel or saving a couple of the 2.5 gallon cartons. They work great since they supply a short plastic hose.

The DEF pump at our nearby truck stop has a tiny nozzle dispenser that fits precisely in the DEF filler, no need to use the plastic funnel, and it meters slowly. Much easier than wrestling the nozzle while holding an 18lb carton. Plus, you can dispense the precise amount needed.

I do feel a bit silly sidling up to the big rigs; about the only time my truck feels small.

[ghaynes755]

Thanks Lara. Good to know.