Tech Toolbox: Grown up sleds

As children, we laid awake looking out into the yard watching the snow fall. Coming in silent torrents, a blanket of snow transforms the land into a plush dreamscape of no school and downhill sledding. Through the years, the sled may change from a wooden frame with metal runners to a four wheel drive vehicle, but the feeling of exhilaration is the same. By the way, when was the last time you had your four wheel drive checked over?

 

Modern technology has brought about the convenience of push button four wheel drive; unfortunately, it also allows us to take for granted what four wheel drive means. A four wheel drive vehicle’s drive trains consist of three extra components: a front axle, drive shaft and a transfer case. A two wheel drive vehicle’s engine rotates the transmission which rotates the rear axle using the rear drive shaft. On a four wheel drive vehicle, the transmission rotates the transfer case which is capable of rotating either the rear drive shaft and front drive shaft at the same time or just the rear drive shaft. This system is referred to as selective four wheel drive, meaning the driver can select between four wheel and two wheel drive. On some vehicles, the transfer case always rotates both drive shafts resulting in full time four wheel drive.

On both selective four wheel drive and full time four wheel drive vehicles, the transfer case needs to be shifted between two wheel drive and four wheel drive modes. On push button models, this is achieved by an electronic motor referred to as an encoder motor. The front axle actuator is an electronic motor that locks the front axle to gather for four wheel drive operation. Both of these are controlled by a computer called the Transfer Case Control Module or TCCM.

In addition to providing four wheel drive and two wheel drive, the transfer case also has the capability to provide additional gear reduction to help in severe conditions. This function is referred to as low range four wheel drive.

Now that you know more about what happens when you push the four wheel drive button, you may ask yourself what it takes to ensure it is working when you need it. Both front and rear axles simply need the fluid changed and inspected for leaks or excessive play. The transfer case also needs its fluid changed, inspected for leaks and a functional check of the shifting mechanism. Front and rear drive shafts should have the splines and joints lubed and inspected for free range of motion.

Everett’s service staff will be glad to service your four wheel drive system; however, we are committed to more than just service. Our service staff not only has the knowledge to fix your vehicle, we also want to help you understand your vehicle. That’s the Everett Advantage and that’s what makes us better.

David Gibbs
Certified Service Technician
Everett Chevrolet Buick GMC