Why Do Nbs Sierra Denalis Have Lower Towing Capacity?

[BruceW]

A NBS Sierra Denali has a 8,500 pound towing capacity versus up to 10,500 pounds for some other models.

 

The SD has more horsepower, more torque, less stress per axles or wheel due to the AWD and stiffer suspension in the Z60 models.

 

I guess is could be that the 20" wheels come with basically car tires that probably have lower weight handling capacity.

 

I am doubtful that the AWD system can not handle towing heavier loads. There is a lot of stress in accelerating 5500 pounds from 0 to 60 in 6.5 seconds. The AWD system is built to handle the 403 HP / 413 TQ. Attaching a trailer does not increase that force, just causes it to be used more often.

 

So what causes the decreased towing capacity and how can it be increased?

[Stevens03]

I doubt the GMT-800's had a 10,500 towing capacity as well. The driveline is the same/similar in both with the exception of the 4L70e in the GMT-800 and the 6L80e in the GMT-900. Both have 8.5" ring gears, both have the 10 bolt, both have rear leafs, only real difference is the front has coil springs verses the GMT-800 torsion bars.

 

The 10,500 rating comes from a Crewcab Vmax with the max towing package, RPO code NHT giving you the 9.5" ring gear with the 14 bolt axle.

 

I'm not 100% positive, but the GMT-900 have 3.42 std gear ratio and the GMT-800 had 3.73 as an option. If there's any difference between the two, it would be gear choice

[AK FiveO]

The tow capacity ratings of trucks is primarily based on the chassis capacity, not horsepower or even "suspension rates". An AWD Denali is one of the heaviest loaded trucks on the chassis..therefore the towing capacity is "penalized" due to the "total capacity" of the chassis. Another factor on towing capacity is the optional cooling package. A gmt900 truck with the 403hp 6.2L only has 200lbs more towing capacity than my 5.3L with the optional "engine cooling package". The other major factor is gear ratio. heavier tow capacity ratings have lower gear ratios.

 

Same for 4wd truck ...the added weight of the 4wd gear penalizes the towing capacity. The truck with the highest tow capacity is usuallya 2wd extra cab/standard cab version because they have the least weight on the chassis from the factory. If you have an owners manual, there is a large chart in the back of that manual showing the towing capacities ...with notes about the engine cooling, cab configurations and axle (gear) ratios.

 

So ..."Total Chassis" rating (i.e. Cab/bed configuration, and 4wd-vs-2wd); "Engine cooling capacity"; and "Gear ratio" are the three biggest factors in rating towing capacity.

[Raymond Lowe]

A NBS Sierra Denali has a 8,500 pound towing capacity versus up to 10,500 pounds for some other models.

 

The SD has more horsepower, more torque, less stress per axles or wheel due to the AWD and stiffer suspension in the Z60 models.

 

I guess is could be that the 20" wheels come with basically car tires that probably have lower weight handling capacity.

 

I am doubtful that the AWD system can not handle towing heavier loads. There is a lot of stress in accelerating 5500 pounds from 0 to 60 in 6.5 seconds. The AWD system is built to handle the 403 HP / 413 TQ. Attaching a trailer does not increase that force, just causes it to be used more often.

 

So what causes the decreased towing capacity and how can it be increased?

 

 

The towing ratings for the 2010 Sierra Denali are 9600 lbs for the 2WD and 9300 lbs for the 4WD.

 

http://www.gmc.com/sierra/denali/specsCapabilities.jsp

[Matt_]

i think the early gmt900 sierra denalis tow ratings were under rated for its true capability... they have since fixed the rating, but im not sure if GM put out a tech bulletin to state that this rating applies to previous model years.

 

the only difference between my 08 and the new 2010 is bluetooth, usb, and a few other creature comfort items that do not affect towing.... yet i have an 8500lb capacity and the 2010 is 9300...

 

i only tow over 6000lb twice a year so im not really bothered by the ratings... if i wanted to tow over 8000lb on a consistent basis id get a 2500HD. i think the ever increasing "tow ratings" of 1500 series trucks is more influenced by market competition than it is by actual towing capability improvements.

[cerbomark]

I thought it was cause of the AWD.

[Matt_]

mechanically, the awd is as strong as or stronger than 4wd.... in either system you'll blow and axle before you break the tcase. and the new gmt900 awd system does not use a clutch (4x4 tcase) or a viscous coupling (gmt800 awd), both of which could slip/wear under very high loads. the gmt900 is a planetary gear system which is mechanically stronger, but will have reduced performance offroad.

 

edit: i used the term "stronger" very loosely here. the premise of the planetary gear design is to have a non-slipping/mechanical connection. point is that none of the tcases are the "weak link" in any of these systems in terms of towing performance for our trucks. the