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One of Ford’s key selling points for the SuperCrew F-150 is the flat load floor in the second row. To achieve that level surface, Ford modified the third and fourth cross-members in the frame.
The third cross-member runs under the frame, directly below the driver’s feet. It protects the transmission and transfer case from offroad obstacles and has been boxed for added trailer-towing capability. It sits lower than the same cross-member in the 2004-08 F-150 because Ford seated the driveline lower to remove the second-row hump that’s normally caused by the driveline running under the cabin floor. When you look at profile shots of the F-150, you can clearly see the third cross-member hanging low, even when the truck has side steps.
You’ll notice the impact of this modification in certain offroad situations, especially in standard four-wheel-drive F-150 models (as opposed to the purpose-built FX4 offroad series). We thought we were killing the side steps trying to get over tall obstacles, when we were actually scraping the third cross-member. A Ford engineer at the driving event said one of the durability criteria for the third cross-member was that it had to support the entire weight of the truck (about 5,200 to 5,800 pounds) without reducing clearance between the cross-member and the transmission.
The fourth cross-member arches above the frame under the second row. Because the driveline sits lower, the top has been leveled and broadened to support the flat load floor.
True Off-Road Capability
While Ford has stretched luxury to new heights in the F-150’s new Platinum trim package, we’re most enamored with the revamped FX4 offroad model. Unlike the sticker-buffed Dodge Ram TRX4, Ford gives the FX4 Barry Bonds levels of offroad juice, starting with an electronic locking rear differential supplied by GKN. It’s the first time an F-150 4x4 has had this feature, and it was specially made to fit inside the F-150’s standard 9.75-inch rear ring and pinion case. The system locks the rear axle on demand to provide traction to both back wheels to help get the truck out of sticky spots in snow, mud, sand or rocks. In practice, it was easily activated by pulling out the dial on the transfer case selector.
A key point we like about the locker is that it works at up to 66 mph in 4-Low, so you can get the rear wheels really spinning if you’re tightly jammed, and up to 25 mph in 4-High. Exceed those speeds and it automatically disengages. The locker also stays engaged in Reverse, unlike some other systems that have to unlock when backing up.
Even though the locker provides extreme capability, it won’t prevent you from getting stuck if you enter terrain that’s beyond the truck’s limits. We managed to do exactly that by not gaining enough speed before entering a mud pit so deep and sticky it claimed our FX4 and two Super Duty rescue trucks. Oops. Eventually we had to be pulled out backward, but the locking rear diff’s rear operating mode made that operation easier than it would have otherwise been.
In soupy-mud conditions, we found the FX4 had no difficulty overcoming ooze that was deep enough to touch the third cross-member, as long as the truck’s excellent 17-inch wheels and Goodyear Wrangler A/T LT275/70R17 tires could find the least bit of solid ground underneath to grip. Three-quarter throttle and aggressive offroad-mode shift points -- courtesy of the new six-speed transmission -- powered the truck through the muck.
Steep hills and low-speed terrain can be tackled with the FX4’s best-in-class 41:1 crawl ratio in 4-Low.
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