Click the photo for a gallery of high-res shots from the GM Truck Challenge

To mark the availability General Motors' latest heavy-duty GMT900 full-size trucks, the automaker invited us out to its Milford Proving Ground to drive its big trucks along with all of the competition. GM had a variety of both light and heavy-duty full-size trucks with gasoline and diesel engines on hand. For comparison they brought along F-150s and Super Duties from Ford, Rams from Dodge, Tundras from Toyota and Titans from Nissan. The Super Duty, Tundra and Titan were all 2008 models.

In spite of rising gas prices and a sagging housing market, the market for full-size pickups is still a huge segment of the overall market. So far through the first five months of 2007, over 900,000 full-size pick up trucks have been sold representing over 13% of the total market and $60 billion in annual revenue. The last number is the reason why the domestics put so many resources into developing new trucks, and Nissan and Toyota want a piece of that pie.

Read all about how the latest GM trucks did against their competitors after the jump.

Update: There is now a video of the stability control event after the jump.

GM marketing analyst Paul Ballew spoke about GM's truck sales and explained that the company is seeing less gas price elasticity with their recent pick-ups than the competition. When the elasticity is closer to one, it means that for a given rise in gas prices, sales will drop off by a certain amount. For the market as whole, GM is seeing an elasticity of 0.3-0.4, while the GM trucks have an elasticity of about 0.2. Essentially, it means that buyers are liking new GM trucks so much that they buy them regardless of gas prices. In addition, as gas prices have risen, the company is finding that 75% percent of full-size truck buyers are staying in the segment, while only 40-50% percent of big SUV buyers are sticking with SUVs.

GM arranged a wide variety of test scenarios that would show off all of the capabilities of the new trucks, including towing, traction control hills, ride and handling, low friction braking and stability and high friction braking.

For the towing tests, GM had a Silverado HD with the Duramax 6.6L diesel and a Ford Super Duty with the 6.4L diesel, each towing a 12,000-lb trailer. The gasoline-powered heavy-duty pick-ups were pulling 9,000-lb trailers. The first test was pulling the trailer up a 7.2% hill. We lined up the diesel-powered Silverado and Ford and had a drag race up the hill. The Ford diesel has a distinct response lag when accelerating from a stop under normal conditions, but brake torquing helped it launch more quickly than the Silverado. By 1,000 ft the Super Duty was out of steam and the Silverado had caught up and was pulling away. When we switched to four-wheel drive it was no contest, and the Silverado left the Super Duty in the dust. The GM and Ford trucks both had an integrated trailer brake control with adjustable gain. On the Super Duty, there is a separate display down low on the dash near the drivers right knee, which wouldn't be a problem normally since once the gain is set, the display doesn't need to be seen all the time. GM puts the display in the Driver Information Center in the instrument cluster. The advantage is that if something happens such as the trailer brakes being disconnected, the fault will show up directly in front of the driver rather than out of his or her normal line of sight.

When we returned to Black Lake there was a handling course set up to evaluate the stability of the trucks when pulling a trailer. Interestingly, the diesel trucks with the 12,000-lb load felt more stable, perhaps in part due to the extra weight in front of the diesel engines. At about 45mph through the series of curves, the diesel-powered trucks felt rock solid. Pushing beyond that, the Ford started to slide a little but was still stable, while the Silverado felt more nailed down. The lighter gas-powered trucks were less stable at the same speeds with the Dodge Ram having the poorest grip, although that is probably due at least in part to the 17" rims compared to the 20" units on the Ford and GM trucks. The GM and Ford trucks never did feel like the trailer was leading the way in through a slalom. For those that are used to the traditional clatter of diesel engines, the newest generation are a huge step forward. The Super Duty was perhaps slightly quieter than the GM Duramax diesel, but the quality of the sound was a bit worse. The Navistar still had a bit of the ticking sound, but very muted compared to previous engines. The GM diesel had an aggressive growl that sounded more like a high performance gas engine than a diesel.

The traction control hill was particularly revealing. There were GM, Ford and Toyota trucks available for comparison, each of which had an engine only traction control system combined with a limited slip differential. The Ford, like the Dodge Ram, uses a clutch pack limited slip differential. While these devices are relatively cheap, the problem is that if the speed differential across the axle is small, the LSD will transfer some torque over to the wheel with grip. The key there is "some torque". If one wheel spins way up, a little bit of torque will be transferred but the other wheel just keeps spinning. If the throttle is feathered lightly the truck can be made to climb the hill, very slowly. The Toyota uses a helical gear limited slip differential that operates in a similar fashion, transferring some torque, but the traction control cuts too much torque from the engine, causing it to roll backwards down the hill and occasionally stalling. If you are very, very careful with the throttle, you may be able to get it to climb the hill. Bottom line: if you ever plan to tow a boat up a slippery boat ramp, avoid the Tundra,. The GM trucks use an Eaton G80 locker differential that senses the wheel speed difference across the axle and completely locks it up when slip is detected. This, combined with some engine torque reduction, allows the GM trucks to climb the traction hill consistently and smoothly. The downside to the locker is that after it locks you need to drive a little to get it to unlock. If you make a sharp turn right after it locks, you can feel the wheels scrub, but that's a minor annoyance compared to how well it works.

After lunch I attacked the skid-traction pad, ride and handling loop and brake tests. On the wet basalt tiles of the skid-traction pad, the Silverado faced off against the Tundra and here the Tundra showed another major lapse by Toyota. A decade ago, it was common for four-wheel-drive trucks to disable features like traction control in four-wheel drive because of mechanical coupling issues between the front and read axles. In 2007, most slip control systems have overcome this and work in all modes. On the GM trucks, the standard stability control system including ABS and TCS works in all drive modes. On the Tundra, switching to four-wheel drive disables everything except ABS, so if you have four-wheel drive engaged and the truck starts to slide or spin, the driver is on his or her own. Even in two-wheel drive, the slip control system is one of the noisiest and intrusive I've experienced on any vehicle in many years. There is more pedal feedback during ABS, a more intrusive and abrupt stability control and far more noise than the Silverado. The system on the GM truck has very light pedal feedback, just enough to indicate that the system is working without being annoying, and the stability control is seamless if maybe just a bit too loose for this type of vehicle. The mechanical noise of the system on the GM trucks is barely audible. On the Toyota, if the steering wheel jerking in your hands and the grinding sound of the brake control unit wasn't enough to tell you the system is active, there is also an irritating beeping the whole time.

Not so many years ago, the idea of taking full-size pickup trucks, especially heavy-duty models, through an autocross course at any kind of aggressive pace would have been laughable. On a sunny spring 2007 afternoon at the GM Proving Ground, it was actually a lot of fun. Even the lowliest of these beasts didn't embarrass itself in handling. By far, the most sporting vehicle on the track was the 403-hp Sierra Denali, which felt remarkably responsive for a 5,300-lb truck with an empty bed. It's amazing what lots of sticky rubber on the ground can do for you. Even that only goes so far when putting that much power down through a live axle, and here GM has done an excellent job of chassis tuning. After the Denali, the next most sporting was probably the Nissan Titan, with the rest of the trucks pretty much clumped together in terms of subjective feel with the Ford's having the loosest feel, but this may due to the tires as much as anything.

Another area where the latest trucks, particularly the GM trucks, showed massive improvement is braking. In the past, GM trucks in particular were notorious for having a brake pedal that felt like stepping on a wet sponge. It was not unusual to take up half the pedal travel before you got any deceleration, but not anymore. The new trucks have firm, consistent pedal feel and good modulation, and even after getting beat up on the autocross course they still performed well.

The Tundra on the left, Silverado on the Right

On the inside, the GM trucks offer two distinct interior designs. One is the more car-like layout shared with the full-sized SUVs and the other is a more utilitarian layout targeted towards the work trucks. Both of them are well laid out and seem to be made from higher quality materials than in the past. In the crew cab models, another distinction between the GM and Toyota trucks was also visible when the rear seat was folded up. The mounting hardware in the GM trucks is designed to leave the load floor in the back of the cab virtually flat with the seat folded. In the Tundra, large mounting brackets remain in place on the floor, making loading a little more problematic. The cheaper looking materials of the dashboard are also readily apparent in the Tundra when compared side by side with the competition. Yet another glaring lapse on the Tundra is the bolt heads in the bed that extend just above the load rails, and anyone out there that has loaded the back of a pickup up truck nows the importance of that little detail.

The much stiffer frames of all modern trucks have definitely raised the bar dramatically in the entire segment. All of these trucks, right up to the heaviest diesel models, have decent ride and handling. Most have much better interiors than they used to, with the notable exceptions of the Toyota and Dodge. Of course, mileage is still an issue, with mileage for all of these trucks dropping into the single digits if you're hauling a load. This is an area where GM will be gaining a huge advantage next spring when its new Two-Mode hybrid system is added to its pick-up trucks. The hybrid system will only be available in the light duty models, but it will definitely make a difference. The new GM trucks may not overwhelm their rivals in every category, but they are so good across the board that we don't feel like shills telling you that they're clearly the best full-sized trucks available right now. Now, we may tell a different story in 2008 when the 2009 Ford F-150 arrives, but until then...

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