by matheny9 [OP] » Sep 19 2010, 12:06am
by matheny9 [OP] » Sep 19 2010, 2:02am
by Z15 » Sep 19 2010, 11:43am
by lzn197 » Sep 19 2010, 2:05pm
by Z15 » Sep 19 2010, 2:14pm
XFE models are only available in two-wheel drive with GM’s E85-capable LC9 5.3-liter V-8 and new six-speed automatic transmission. The LC9 uses an aluminum engine block and aluminum cylinder heads to save weight. It also features active fuel management, which switches the V-8 between four-cylinder and eight-cylinder mode, depending on engine load, to save gas. Power has been boosted slightly, to 320 horsepower and 340 pounds-feet of torque, up from 315 hp and 338 pounds-feet of torque in non-XFE trucks with the same engine.
GM has lowered the XFE’s aerodynamic drag to a claimed best-in-class .412, narrowly beating the all-new 2009 D***e Ram’s .419 coefficient of drag. Helping the XFE achieve that slippery wind rating are a soft tonneau cover, an extended front chin spoiler and a 10-mm-lowered suspension and ride height. Low-rolling-resistance tires and lightweight 17-inch aluminum wheels help reduce friction between road surfaces and the truck.
The XFE also uses an unusually tall 3.08 rear axle to hit its higher fuel economy numbers. To understand why this is important, it helps to understand how rear axles are rated. Rear axles are assigned numbers that describe how many rotations the driveshaft must make to turn the rear axle (and rear wheels) once. A 3.08 rear axle turns the wheels once for every 3.08 driveshaft rotations.
The rear axle ratio can make a big difference in performance and fuel economy. The numerically higher the ratio (counter-intuitively, the shorter it is), the faster the driveshaft turns and the sooner the driveshaft can transfer peak horsepower and torque from the engine to the rear wheels. The result, generally, is faster acceleration and higher towing capacity than a rear axle with a numerically lower (taller) ratio. The tradeoff for a shorter axle ratio, though, is usually lower fuel economy because an engine that's working harder is also burning fuel faster. The taller the rear axle, the more effort the truck requires to get a running start, the less it can tow and the more efficiently it will run at highway speeds.
by lzn197 » Sep 19 2010, 2:26pm
by rangerjoe » Sep 20 2010, 3:03pm
by NIBS » Dec 16 2010, 4:45pm
by ffhillclimber » Oct 21 2013, 7:10pm
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