9.5" Hybrid Axle

music · February 14, 2011

Looking at the NHT (max tow) package, GM lists the rear axle as a 9.5" hybrid axle. Folks on the forum here often refer to it as a "14-bolt rear axle". The 2500 (non-HD) and previous-generation 1500HD have a 14 bolt SF rear axle with a rating of ~5500 lbs. They also have 8-lug hubs, and the vehicles themselves have the HD brake system (hydro-boost).

I can't look at one first hand, but what does it mean by "hybrid" on the NHT pkg? They appear to have the same 6-lug hubs, but with disc rather than drum brakes, is that correct? I'm assuming it's some kind of mix between the 14 bolt used on the 1500HD and 2500 series and the 8.5" axle used on the 1500? Does anyone know the GAWR rating for the axle? According to GM's site, the rear axle on a 4wd is 4000 lbs (with no mention of a separate value for the NHT). Maybe someone can look at their door jamb and get the value there?

MS3DALE · February 14, 2011

I'm assuming it's some kind of mix between the 14 bolt used on the 1500HD and 2500 series and the 8.5" axle used on the 1500?

Bingo,Thats it,Its called a "Hybrid" axle because its a mix of both 8.625" and 9.5" axle parts.

The rear GAWR on mine is 3950 lbs.

Stevens03 · February 14, 2011

9.5" 14-bolt axle with 6 lugs and the two I've had both had disk brakes.

music · February 15, 2011

Thanks guys. Very interesting. The rear rating is apparently the same for both the 8.625 and 9.5 axles (3950 lbs spring / 4000 lbs axle). I was asking this because I've considered adding a leaf (or small overload spring) to the rear of my truck for towing (stiffen it up a tad), and was looking at the axle ratings. I assumed the NHT would have a higher load bearing capacity due to the +300 lbs of payload rating, but (once again)... so much for assumptions.

Stevens03 · February 15, 2011

Thanks guys. Very interesting. The rear rating is apparently the same for both the 8.625 and 9.5 axles (3950 lbs spring / 4000 lbs axle). I was asking this because I've considered adding a leaf (or small overload spring) to the rear of my truck for towing (stiffen it up a tad), and was looking at the axle ratings. I assumed the NHT would have a higher load bearing capacity due to the +300 lbs of payload rating, but (once again)... so much for assumptions.

Why don't ya just do it. Your constantly trying to convince yourself that there's not much difference... but I assure you that the little bit of changes are a big difference. Especially the 6-speed.

I tried and lost the battle...

MS3DALE · February 15, 2011

Thanks guys. Very interesting. The rear rating is apparently the same for both the 8.625 and 9.5 axles (3950 lbs spring / 4000 lbs axle). I was asking this because I've considered adding a leaf (or small overload spring) to the rear of my truck for towing (stiffen it up a tad), and was looking at the axle ratings. I assumed the NHT would have a higher load bearing capacity due to the +300 lbs of payload rating, but (once again)... so much for assumptions.

The NHT has higher capacity springs.

BTW....The 9.5" hybrid axle also came with rear drums for a time,on GMT900 trucks without the NHT pkg. and Stabilitrak.

music · February 15, 2011

Why don't ya just do it. Your constantly trying to convince yourself that there's not much difference... but I assure you that the little bit of changes are a big difference. Especially the 6-speed.

I tried and lost the battle...

It isn't nice to taunt Seriously... I don't question the power/gearing benefit for a second. I'd love the 6.2/3.73/6-spd combo, but I haven't justified the expense for how much I'd use it. Notice I said "haven't", not "can't" If I got serious about changing, I'm pretty sure the 5.3/6-spd would be "about right" for my load w/ regard to power/gearing. Most of my driving is unloaded, and the upfront cost is ~$2k less vs ordering a NHT. I wasn't looking at axle ratings for that reason (I was verifying what I had in mind for my truck), but realized there was only one number listed.

BTW, you've mentioned your mpg a few times in the new truck, but I don't recall what fuel? Are you running 13 to 17 mpg on 91 octane, or 87?

music · February 15, 2011

The NHT has higher capacity springs.
BTW....The 9.5" hybrid axle also came with rear drums for a time,on GMT900 trucks without the NHT pkg. and Stabilitrak.

Thanks Rich. I recall you posting those part numbers a while back. I'll search and see if I can find them. Curious about the cost of them vs an "add a leaf" kit.

Stevens03 · February 15, 2011

I've been running a mix of 89 and 93 and haven't really seen a change in mileage but do notice a little difference in throttle response, so I choose to run the 93 for the fun factor.

3birds · June 15, 2011

I just took delivery of our new K1500 4X4 NHT on the 4th of June. The first tank gave me 17 mi/gal on mixed fuel (the dealer's regular and my premium) during a break-in run on the highway. It does about the same as our '97 C2500 4X2. I will be interested to see what it does with a trailer behind it.