4WD -4X4 - Encoder / Shift motor testing and R&R GMC / Chevy trucks and SUVs.

The 4WD or Four-Wheel-Drive system in most trucks and SUVs sends some of the engine torque to the front wheels when needed. depending on the terrain and rodes conditions like snowy rainy/muddy the system can be full-time or part-time 4WD, the old 4WD systems useda manual locking wheel hubs and a floor shifter lever like the ones on manual transmission trucks or SUVs and the driver has to lock the front wheel hubs at each wheel by turning a dial to the lock or unlock position, in the new 4WD system it uses a control module/range selection switches / front axles locking actuator and an Encoder/shift motor, the driver has four ranges to choose from the 2high range normal roads conditions and only rear-wheel drive, the 4high range this is used on wet slippery roads/terrains only and engine torque is sent to the front wheels and the front axles actuator is locked if the 4high range was driven on dry roads it will damage the transfer case, the 4Llow range is only used in muddy snowy terrain or to get the truck unstuck in this range the transmission will not upshift to higher gears the truck should not be driven in this range on dry roads.