on the Rocks:
If you’re buying a full size truck, it’s likely you’ve got a good reason for doing so. Maybe you need a large cargo box to carry your work supplies, or you have a trailer that needs to be towed. In either case, it’s easy to match the capabilities of the truck you’re buying to what the manufacturer says it can do. For example, when Toyota says a 2007 Regular Cab Tundra with a 5.7-liter V8 can pull a 10,800-pound trailer, then you know it’s probably not wise to exceed this number towing.
But purchase decisions aren’t so clear when it comes to determining whether to buy a truck for its off-road and four wheel drive capabilities. Manufacturers provide information about ground clearance, approach and departure angles, and break-over angles, but it’s a fool’s errand to try to match those inches and degrees to every rock, rut and hillside you can expect to drive on or over.
And it gets more complicated when buyers learn that some off-road packages are more equal than others. You can buy a pickup with just the 4x4 basics, such as locking hubs, special front and rear differentials to control wheel spin, a transfer case to lock the front and rear axles together, and stock suspension components, or you can upgrade to a 4x4 package with a very capable sounding name, such as GM’s Z71, Dodge’s Power Wagon, or Ford’s FX4, that typically adds items like sturdier shocks, stiffer springs, beefier sway bars, and underbody shielding.
Toyota’s upgraded off-road package for the Tundra is the Toyota Racing Design (TRD) option. Check this box when ordering and you’ll see the biggest change in the truck’s springs and shocks. 4WD TRD Tundras get stiffer linear-rate front coil springs that compress evenly when loaded, while 2WD (PreRunner) TRD Tundras get dual-rate front coil springs that compress at two different rates that vary with load. Both 4WD and PreRunner models receive Bilstein gas-charged monotube shocks with large 46mm pistons for better bounce and rebound control. TRD also substitutes in unique 18-inch rims with BF Goodrich T/A 18-inch off-road tires and front tow hooks attached directly to the front frame rails for extra strength. A bold sticker package and fog lamps round out the kit.
Toyota doesn’t offer 4WD for V6 powered Tundras. Only V8 powered trucks allow the driver to shift-on-the-fly from 2WD into 4WD, using a knob on the dash. An all-new transfer case helps reduce the effort switching to 4-Hi or 4-Lo modes. It uses a 1.5-inch drive chain, that’s been widened 1/4-inch over the previous Tundra’s, to manage the new 5.7-liter V8’s 401 lb-ft of torque.
All 2WD Tundras have a standard automatic limited-slip differential (LSD) to reduce wheel spin, while all 4WD Tundras use Toyota’s new electronically enhanced Active-Traction (A-Trac) system for improved dirt gripping action. A-Trac works like a locking diff but it won’t bog down during tight turns at low speeds because it uses selective brake pressure to each wheel to control slip instead of gears. Toyota claims that A-Trac reacts quicker to changing traction conditions, and delivers up to 15 percent better torque transfer than mechanical LSD systems, plus reduces yaw on washboard trails for a better ride off-road.
Unlike the A-Trac system used in Toyota’s FJ Cruiser SUV that can be turned on or off with a switch, A-Trac in the Tundra is fully automatic when 4WD is engaged and the front and rear axles are locked together. You can't manually disable it.
Also helping improve off-road traction is a new planetary reduction gearset with six pinions, instead of the previous Tundra’s four, that provides a lower reduction gear for better descent control.