In addition to the engines, suspensions, transmissions, and other choices, GM also added some cool technologies to the pickups. One we fell in love with on the SUV is the Eaton G80 rear-locking differential. Under regular dry pavement conditions, the system works like a regular open differential, but, as soon as wheel slip occurs, either in forward or reverse, the system immediately kicks in.
The way Eaton describes the system, the differential is set up with a flyweight governor that responds to differences in wheel speeds, and disc packs that are mounted between the side gear and the case. Whenever one wheel spins faster than the other, the governor spins rapidly, causing the flyweight to open. That flyweight catches on a latching bracket and the lockup process starts. During lockup, a self-energized clutch system causes a cam plate to ramp against a side gear. This ramping action compresses the disc packs. The ramping continues until both axles, and therefore both wheels, are spinning at the same speed. Now the system is at is full lock, which prevents any further wheel slip. (Note: Axle lockup only occurs at speeds below 20 mph.) The entire process occurs instantly, and is virtually unnoticeable by the average driver. When both wheels regain traction, unlocking occurs and things go back to normal.
The biggest benefit to the system is on slippery boat ramps or in serious off-roading conditions. Although we didn’t have a chance to try it out during our test drive, previous exposure to the G80 system with the SUVs shows that the rear locker really does provide grip without spinning the wheels.
Another added benefit to the Silverado/Sierra is the addition of safety features like StabiliTrak, GM’s oversteer/understeer stability control program with rollover mitigation technology standard on Crew Cabs and available on Extended Cab models. Also available are roof-mounted head curtain airbags, and GM’s industry-exclusive rear impact sensors for rear-end collision protection.
First, if you currently own a Silverado or Sierra, you’ll be impressed with the ride and handling improvements on the 2007s. Just as SUVs have stopped feeling truck-like, so have the full-size pickups. That’s not to say you’ll think you’re cruising down the highway in a Corvette, but gone is the wandering steering feel, the bumps and rattles, and even the unpleasant ride that most pickup owners had to compromise on to get the utility features.
Whether we were in the Work Truck or the LTZ, in either the Silverado or Sierra, we were impressed with the amount of sound-deadening throughout the cabin. The fit and finish all around was near perfect, and the ease of use of all the knobs and switches were equally welcome. Our one gripe inside was the door handle location is a bit low and awkward; if GM fixed that, this interior (especially on the LTZ) would be award winning.
At the Proving Grounds, we jumped in and out of a handful of different trucks, including a GMC Sierra SLT 2WD with the 6.0-liter engine and the MHT suspension with a 3.73 rear gear. We drove the Silverado Crew Cab LTZ Z85 loaded with a payload of wood, and then another Sierra 4x4 unloaded. We also did a towing exercise versus the competition. And a few weeks later we spent some seat time in the GMC Sierra as part of a combined ride and drive with the new Acadia.