A Transfer Case is a fundamental part of the 4-wheel drive system on your 2007.5-2010 GM 2500HD/3500HD. 4-wheel high will maintain the same gear ratio as 2-wheel drive and is for high-speed situations such as driving on dirt or snow-covered roads. It is responsible for transferring power to the front wheels and rear wheels in 4-wheel drive systems. There are usually two different gear ratio options with a Transfer Case, 4-wheel low and 4-wheel high. The Transfer Case mounts to the back of the transmission and is what the front and rear drive shafts connect to. 4-wheel low is for low-speed situations where maximum torque is required such as driving up a steep rocky hill or pulling out a stuck vehicle.
It is highly recommended to not engage the transfer case for anything other than off-road or low-traction situations. Wheel slip is possible in loose terrain, alleviating any binding that can occur on dry pavement. Since transfer cases lock the front and rear axle together, the wheels are unable to spin at different speeds making turning and cornering on dry pavement difficult. Transfer Cases generally are very strong from the factory and do not require internal upgrade unless the vehicle is used for extreme off-roading or racing. External upgrades such as transfer case braces are offered for certain applications that add structural rigidity to prevent damage from high torque loads and twisting. XDP carries a wide selection of Transfer Case products available from Dorman, Merchant Automotive, PPE, Sun Coast Converters, and more.