4x4 of the Year- Day 4
4x4 Drive Systems
“Who gets the power to the ground?”
While horsepower is important, getting that power to go the ground is even more critical at Petersen’s 4-Wheel & Off-Road 4x4 of the Year test. This year we have one vehicle with solid axles and selectable lockers front and rear, a slew of pickup trucks with independent front suspension and rear solid axles, and a pair of SUVs with completely independent suspension front and rear. Unfortunately none of them have a true shift lever, but rather buttons or knobs to engage low range. Taking a closer look at these systems reveals how different manufacturers choose various ways to get to the same goal: traction on the trail.
Chevrolet Colorado Z71
The Chevy Colorado uses fairly standard pickup truck architecture. A full frame mounts the front coilover, a-arm suspension and rear leaf springs. A six speed automatic routes power to the transfer case that has a 2.72:1 low range. The gear ratio is 3.42, which seems tall until you consider that the powerband of the Duramax diesel is considerably lower than a gas engine. The G80 Gov-lok in the rear really helped the Colorado on our loose hill climb.
Jeep Renegade Trailhawk
The award for most transmission gears goes to the nine speed Jeep Renegade. Rather than a traditional transfer case, the Renegade uses a Power Transfer Unit to route torque to the rear axle with a paltry crawl ratio of 20:1. The unibody Renegade uses independent suspension with a-arms front and rear. The Trailhawk model is Trail Rated and adds a slew of off-road features that make it qualify for our test. Barely.
The G550 checks all of the boxes for things we like to see in a 4x4, but it also has the highest price tag in the test. A full frame, solid axles, and even selectable lockers front and rear are available from Mercedes-Benz. The axles have 4.38 gearing and are suspended by coil springs with radius arms and track bars. The only limitations for where the G550 would go are the low hanging exhaust and street-oriented tires.
Mercedes-Benz Sprinter Van
The five speed automatic transmission is well matched to the diesel engine in the unibody Sprinter, but the transfer case is a disappointment. It cannot be locked to provide 100% power front and rear, and it only provides a gear reduction of 1.4:1. The rear axle is a traditional solid axle with leaf springs, but the front axle uses a transverse mounted fiberglass monoleaf for the independent suspension.
Nissan Titan XD
The Cummins engine seems to get all of the attention in the Titan XD, but it is backed up by some equally impressive hardware. The six speed Aisin transmission is mated to a chain driven transfer case with a 2.71:1 low range that is nestled between a full boxed frame. The AAM solid rear axle in the Titan XD uses a 10.5-inch ring gear and has a selectable locker for added traction. We did find that the leaf springs had significant axle wrap in the sand with all the torque of the Cummins engine.
The Ram Rebel still has a full frame and IFS with a rear solid axle, but unlike the other trucks in the test the Rebel uses air suspension at all four corners. This allows the suspension to raise up for more ground clearance off-road, but lower at freeway speeds to improve fuel economy. The air springs are combined with Bilstein shocks for a firm, precise ride. The Rebel uses an eight speed transmission that keeps the Hemi engine in the sweet spot at any speed, although we don’t care for the rotary shift selector on the dash. The Rebel has open differentials with 3.92 gears, but with the largest tires in the test traction was rarely an issue.
Range Rover Sport TD6
The Range Rover TD6 has an eight speed ZF automatic that does an amazing job of keeping the diesel engine in its powerband. Range Rover also has some of the best terrain-based traction control we have used, although some judges felt that it disconnects the driver from the experience and preferred turning the controls entirely off. The unibody Rover uses independent suspension front and rear with adjustable air suspension. This configuration provided a lot of ground clearance, but forget about modifying it.
Toyota Tacoma TRD Pro
The Toyota Tacoma uses the same pickup points for the front and rear suspension as the previous model, so aftermarket suspension components are still compatible with the current coilover, a-arm front suspension and rear leaf springs. New for 2016 are the five speed automatic transmission (a six speed manual is also available) and a smaller, lighter transfer case with 2.57:1 low range. The TRD Pro comes with a selectable rear locker in the new, larger 8.75-inch rear differential. The TRD Pro also uses Crawl Control and Terrain Select technology that have trickled down from the Land Cruiser.
No, this isn’t the dash of a Rubicon Wrangler. The G550 comes with selectable lockers for the center differential, as well as the front and rear axles. The price tag is more than double what a JK Rubicon will set you back, but a JK doesn’t come with a twin turbo V8 engine and seven speed automatic transmission.
If something works, but you don’t necessarily like it, does that count in its favor or against it? Our group of judges had this discussion many times concerning Toyota’s incredibly effective Crawl Control.
The Range Rover has arguably the most sophisticated traction control in the test. It worked well in most situations and was the most capable vehicle in the sand dunes, but our loose hill climb gave the Rover fits and caused it to pull power, leaving us at the bottom of the hill.
The Trailhawk treatment adds front and rear tow hooks, skidplates, and a 0.8-inch lift to the Renegade. It also comes with Jeep’s Selec-Terrain with five different terrain settings for a variety of different situations.
Each vehicle is put on a lift and the undercarriage is thoroughly inspected. This is where the judges get a good view of skidplates, ground clearance, and how strong drivetrain components are.