2012 GMC 2500HD towing disappointment

[MJN]

I'm pretty disappointed with how my truck tows- Its a 2012 GMC Denali HD crew cab short bed (2500HD) 6.0L, 6speed auto, 3.73's, 275/70R18 tires. Supposed to be 360hp @ 5400rpm and 380 ft lbs @ 4200 rpm. I pulled our camper (34ft long) and it handled the weight just fine but would not hold 65mph. Dry/empty weight is 6615lbs, it was probably close to 7000 with some of our stuff in it. It was not windy but in tow/haul mode it would stay in 5th gear but then kick down to 4th, I would get up to 65 and it would shift back to 5th and slowly lose speed, then it would downshift again. I didn't want to sit and put my foot down and let the engine spin at 3000+ rpm for an hour. I know its a heavy trailer and 3.73's aren't great for such a big trailer either but I expected it to do better and not struggle so much. We didn't have any issues pulling other than just lack of power.

[Keith Seymore]

That's design intent.

You have horsepower, but what you really want for pulling a trailer is torque.

That's also the down side of having so many gears; sometimes it doesn't quite know which gear it wants to be in.

K

[MJN]

I know, everything is working as it should and the gearing isn't in my favor, I just had higher hopes it would pull with less effort. I've seen 1/2 tons pulling stuff just as big and even got passed by a Denali 1/2 ton with the 6.2L pulling a camper but maybe those people don't mind their engines cranking 3000+ rpm for extended periods. A duramax would be nice but the few times I pull this camper it isn't worth switching at this point, maybe if I towed more.

[kipps]

3000 shouldn't hurt it at all. I'd let it spin.

A 1970's c10 with factory fitments, such as 235/85r16 tires, 4.10 gears, and a sm465 transmission will spin 3000 rpm at 70 mph. An LS engine is much happier at high rpm's than the old-school small blocks were.

[Keith Seymore]

I probably didn't explain myself very well (...because I was in a hurry that day...) but I was a GM company vehicle driver for nearly 20 years. That allowed me to pick any vehicle in the fleet to tow my trailer on race weekends.

Trailer is approx. 7500 lbs fully loaded.

You noticed the same thing I did as we (as a company) moved away from diesels/big blocks and into the small block variants*. You really have to spin them, which results in going down in gears, to maintain your ground speed. I suggest that is what you are perceiving as "struggling".

Even if it is not bad for the engine it is more annoying than simply torqueing your way through.

K

*I worked on six generations of GM full size trucks:
Old C/K/R/V
GMT400
GMT800
GMT900
K2
T1

That puts me in the somewhat unique position of being able to see for myself this transition across the years.

[Greg58]

So which setup did you like the best Keith?
I have an 07 D-Max LBZ 3500, and so far it is my favorite as far as ease of pulling.
Have been towing stuff since the early 80's

Greg

[Keith Seymore]

Originally Posted by Greg58

So which setup did you like the best Keith?
I have an 07 D-Max LBZ 3500, and so far it is my favorite as far as ease of pulling.
Have been towing stuff since the early 80's

Greg

I love the 04 LB7 that I now own.

There's no emissions equipment (the crankcase vents to atmosphere via a draft tube) so no DEF, and the power is awesome.

I have a BullyDog programmer on it with the tune set to level 3 (of 4). You have to be careful when the roads are wet because it will roll through first gear and smoke the tires in second, even with the trailer hooked up.

K

[Greg58]

Originally Posted by Keith Seymore

I love the 04 LB7 that I now own.

There's no emissions equipment (the crankcase vents to atmosphere via a draft tube) so no DEF, and the power is awesome.

I have a BullyDog programmer on it with the tune set to level 3 (of 4). You have to be careful when the roads are wet because it will roll through first gear and smoke the tires in second, even with the trailer hooked up.

K

Mine is all stock, my son (a diesel tech) says I should tune it. But I'm pretty happy with the power the general put into it from the factory. Almost 200K and it purrs like new.
Greg

[Warrens69GMC]

You might want a power programmer (like bully dog) so you can adjust your towing needs to each trailer.

[biketopia]

They need RPM, don't be afraid of 3k, that's nothing. Look at the power curve for your engine, torque doesn't come in until over 2k. A tune on the stock engine from a reputable tuner with EFI live or HP tuners will go a very long way in usable power, fuel economy and satisfaction. Another way would be a tune coupled with a set of long tube headers and torque cam, be like a whole new truck! Or a small supercharger kit designed for those trucks, makes power when you need it towing, and then well behaved when empty.