12/10/2019
HOW PREVENTATIVE MAINTENANCE CAN SAVE YOUR AWD VEHICLES FROM CERTAIN DEMISE THIS WINTER
The popularity of 4WD and AWD vehicles in Canada has massively increased over the last 20 years, mostly in response to our long winters and difficult driving conditions. With that in mind, it is crucial to remind your customers that while the AWD and 4WD systems can be quite helpful for navigating snow and ice, proper tire rotation and sizing is very important and cannot be neglected. As you are aware, 4WD and AWD vehicles are equipped with additional differentials and/or viscous couplings that are designed to allow momentary differences in wheel speeds when the vehicle is cornering or when tire spin occurs. (More information below) When the differentials or viscous couplings are forced to operate 100% of the time because of mismatched tires due to wear or low tire pressure, the differentials, transfer cases and/or viscous couplings will experience binding, disproportionate heat and unnecessary wear until they fail.
Remember to:
1. Regular tire rotation.
2. Avoid replacing only two or individual tires.
3. Keep all tires at properly inflated pressure. Keeping the tires properly matched, inflated and rotated is much cheaper than replacing transfer cases, viscous coupling and differentials.
Four-wheel drive and all-wheel drive vehicles must use tires that are very closely matched. This is because different diameter tires roll a different number of times each mile as a result of the variations in their circumferences. Tire diameter variations can be caused by accidentally using different sized tires, tires with different tread designs, tires made by different manufacturers, different inflation pressures or even tires worn to different tread depths. If a tire is worn 1/8" shorter than the vehicle’s other 3 tires (@ diameter of 24.84") and will roll 839 times per mile. While the difference of 1/8" in overall diameter doesn't seem excessive, the resulting 4 revolutions per mile difference can place a continuous strain on the tires and vehicle's driveline. The greater the difference in the tires' circumferences, the greater the resulting strain. This makes maintaining the vehicle manufacturer's recommended tire inflation pressures and using "matched" tires on all wheel positions necessary procedures to reduce strain on the vehicle's driveline. Using "matched" tires means all four tires are the same brand, design and tread depth. Mixing tire brands, tread designs and tread depths may cause components in the vehicle's driveline to fail. Mismatched tires or using improper inflation pressures for all-wheel drive and four-wheel drive vehicles can also result in immediate drivability problems. Some Control Trac equipped vehicles in 4Auto mode may exhibit a shutter on acceleration and/or a noise from the front driveline and transfer case while driving. Some all-wheel drive and four-wheel drive vehicles may exhibit axle windup or binding while driving. Some four-wheel drive vehicles (manual or electronic shift) with a two-wheel drive mode may refuse to shift "on the fly" into 4x4 Auto or 4x4 High at highway speeds.
