GM’s announcements of the 2020 Silverado HD and 2020 Sierra HD has reignited the topic of heavy duty pickup trucks. Since the introduction, we’ve received several letters asking about the purpose of dually trucks, with readers asking how trucks with two rear wheels differ from regular pickups. So we thought it a good idea to do a quick-and-simple refresher on the matter.
2020 Chevrolet Silverado HD High Country single rear wheel
Singles
A Single Rear Wheel (SRW) truck has one pair of rear wheels; in other words, the truck has a total of four wheels. Single rear wheel is the most common pickup truck configuration and is sufficient enough for most truck tasks, whether hauling or towing.
It also makes daily driving easier, as it is more friendly on gas, while offering adequate comfort and stability no matter the terrain.
GM offers single rear wheel pickup trucks in the following models:
- Chevrolet Colorado and GMC Canyon
- Chevrolet Silverado 1500 and GMC Sierra 1500
- Chevrolet Silverado 2500HD and GMC Sierra 2500HD
- Chevrolet Silverado 3500HD and GMC Sierra 3500HD
2020 GMC Sierra HD Denali dually
Duallies
A dually truck is officially known as DRW, short for dual rear wheel. It contains two pairs of rear wheels, for a total of six.
It’s easy to spot a dually, since that extra set of rear wheels gives the truck a much larger appearance that rarely goes unnoticed. In fact, dually trucks need much more pronounced fenders to cover both wheels. But it’s what’s underneath those fenders that truly matters: the extra set of rear wheels enables dually trucks increased contact with the road, thereby spreading the weight out across two extra wheels and delivering increased stability in the process.
More importantly, the design of the rear axle enables a “full floating” configuration. That’s when the axle shafts only transmit the torque, but don’t actually carry any of the vehicle’s weight. Instead, the bearing hubs (at the outer ends of the axle) carry the truck’s weight. The design is significantly more robust than that of a weight-bearing rear axle.
GM offers the following dually trucks:
- Chevrolet Silverado 3500HD and GMC Sierra 3500HD
- Chevrolet Silverado Medium Duty, offered as 4550HD, 5500HD and 6500HD
2019 Chevrolet Silverado Medium Duty
Benefits Of A DRW Over An SRW Setup
Dually trucks can typically tow more and have a higher payload than their single rear wheel counterparts. How much more? That varies by the truck and the activity.
In the case of the one-ton 2020 GM HD trucks – the 2020 Silverado 3500HD and 2020 Sierra 3500HD – the difference in payload is 2,215 pounds between the SRW and DRW versions. The difference in conventional towing is 5,500 pounds.
The biggest advantage of a dually truck can be seen in gooseneck/fifth-wheel towing: a Silverado 3500HD Dual Rear Wheel can tow a whopping 14,000 pounds more than a Silverado 3500HD single rear wheel.
| 2020 Chevrolet Silverado 2500HD SRW | 2020 Chevrolet Silverado 3500HD SRW | 2020 Chevrolet Silverado 3500HD DRW | |
|---|---|---|---|
| Max Payload (lbs): | 3,746 | 4,302 | 6,517 |
| Max Towing – Conventional (lbs): | 14,500 | 14,500 | 20,000 |
| Max Towing – Gooseneck (lbs): | 18,600 | 21,500 | 35,500 |
- All units in pounds (lbs)
- Payload and towing maximums for Regular Cab models with 6.6L V-8 L5P Turbo-Diesel Duramax engine with 10-speed transmission
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Comments
Need more detail on “full floating” and weight bearing axle hubs, please.
“Environment Princess” Mary Barra loves pushing more gas-guzzling mega trucks that most people do not need.
Agree with Tomko Michelle, please more info on the rear axle
One great benefit is in windy conditions using a SRW can be a with white knuckle experience. Using a DRW is less effects of cross winds. A goose neck also helps for cross winds. The front tires carry less weight with a GN vs ball hitch. The main head ache with both types is the blind spots especially in close quarters like gas stations and bollards. I currently have a ’16 Denali DRW and have cameras mirrors, front grill, wireless for trailer tail. I hooked up the wireless rear camera and wake up, what enlightment as how many cars hang on the trailer blind spot. I really wanting to get the ’20 with the cameras with the over head view and hope u can zoom in closer. I hope there will be a retrofit on the cameras for the gn type of trailers in the ’20 Denali.
What is the difference between fully-floating and semi-floating axle?
Hope this helps explain
Full Floating axle, uses wheel hubs (the part the wheels attach too) that are mounted with two taper bearings to spindles at the outboard end of each axle tube. Similar to how a non unit bearing type front hub mounts to a spindle (like old RWD impala, malibu, nova, chevy II etc.). An axle shaft transmits torque to the wheel from the differential. The axle shaft is splined at the differential, and is bolted to the wheel hub on the outboard end thru a flange which is much smaller in diameter than the wheel hub’s lug nut pattern. Physically, on the full floating axle the axle shaft can be unbolted from the wheel hub and removed from the axle tube while the tire and wheels are still on the vehicle and the vehicle supported at it’s tires. All GM HD (2500/3500) pickups have full floating rear axle, single rear wheel and dual rear wheel. (10.5″ and 11.5″)
Semi floating, the axle shaft and wheel hub are one piece and insert into the axle housing tubes. The axle shafts have a single bearing pressed on the axle shaft at the outboard end, This bearing supports the axle shaft outboard end inside the axle tubes. The inboard end of the axle shaft is splined to transmit torque from the differential to wheel. The axle shafts are retained in the axle housings either by c clips at the differential end (GM), or a bolted retainer plate for the axle bearing (Ford). When the axle shaft comes out of the axle tube there is no associated wheel and tire on the vehicle. All 1500, midsize pickups, single rear wheel vans use semi floating rear axles.
A non floating axle would be a single shaft, mounted via bearings to the vehicle chassis. Think chain drive go kart.
Thanks. I have a 2006 Chevy 1 ton van 12 bolt rear end with Eaton G80 can put 3,400 pounds in the rear. I thought that semi-floating axles couldn’t hold that much
Great job explaining that. I understand it now.
Just perfect. Thanks Homer for the explanation.
There are two primary purposes for the dual wheel rear axle. As alluded to above:
-Load carrying capacity of rear axle
-Stability for handling while hauling a load and or significant size trailer. Gooseneck trailer combinations are typically more stable than conventional trailer combinations due to the trailer’s tongue load being supported further forward and closer to the rear axle centerline. but do not enable much use of the bed for payload while towing, so dual tire rear axle helps stability while towing and hauling at the same time. Think dump truck hauling gravel while towing a skid steer at the same time.
The 2020HD trailer load chart above is not in agreement with previous GM press release for 2020 Silverado. GM claims maximum conventional trailer weight for single rear wheel at 18,500 Lb with 2020 2500 crew cab 4WD. Likely just to beat current Ram single rear wheel max conventional trailer claim in another juvenile example of lets claim something bigger because federal regulations don’t prevent it and customers wouldn’t be stupid enough to do it for too far or often anyway.
I’ve hauled smallish excavators weighing 14,000 lbs on a 4,000-4,500 lb trailer various times and up to 2 1/2 hours one way with my 03 2500HD Duramax with no problem at all, even in quite hilly terrain. Grossed 35,000 to 37,000 regularly (2-3 times a week) with a 30’ tandem dually gooseneck 9 hour round trip getting 11-12 mpg loaded. Nice to see the weight ratings are coming up! Yes I have my cdl and I drove carefully and took my time getting up to speed. Sold truck with over 400,000 miles on it running strong, but body was rusting out. Best performing truck out there with the diesel/trans/body combo.
totally would bust a nut in michelle