Sport-Trac, Auto-Trac, X-Drive, and 4Matic, just to name a few; all of these types of drivelines are being used in recently manufactured vehicles. So, how do you determine which driveline is right for you? Front-wheel drive, rear-wheel drive, on demand four-wheel drive, or all-wheel drive — now, that is a lot of choices and if you don’t carefully consider all of the facts, then you could end up with a vehicle that doesn’t meet your needs. Here is a guide, for potential new and used car buyers, designed to help you choose the right driveline.
Part one of this guide, on drivelines, will cover two-wheel drive models. Be on the lookout for Part 2, which will deal with on-demand four-wheel drive and all-wheel drive vehicles.
This term can refer to either a front-wheel drive or rear-wheel drive vehicle. Any vehicle which is propelled using a single axle system can be considered a two-wheel drive model. A two-wheel drive vehicle should meet the requirements of the vast majority of car owners, therefore, it stands to reason that there are more two-wheel drive vehicles produced than any other.
The most common type of rear-wheel drive vehicle is the front engine, rear-wheel drive. This type of vehicle utilizes a driveshaft to apply horsepower to the rear wheels, which then push the vehicle. As the engine produces power, it is transferred through the transmission (manual or automatic), turning the driveshaft, which is either splined or bolted to the pinion yoke of the rear differential. Most pickups and full-sized vans are rear-wheel driven, as this type of driveline is excellent for applications which move heavy cargo or pull a camper or trailer. Some rear-wheel drive differentials are “open carriers” and only one of the rear wheels actually pulls, others are “limited-slip” type differentials and only one rear wheel pulls unless and until it begins to spin, in which case the other rear-wheel is employed with the use of specialized clutches in the differential. Still, another type of differential is the “locking carrier” type, in which both rear wheels pull all of the time. This type of differential may also be known as a “positive traction” differential. The positive traction rear-wheel drive differential is very popular among drifting enthusiasts.
Key areas of concern when considering a rear-wheel drive vehicle:
- Inspect the rear differential for leaks, especially at the pinion seal and axle seals.
- Listen for grinding noises when driving, the noise may be very obvious under acceleration, and then lessen when coasting.
- Clunking or banging noises when accelerating, or releasing the accelerator pedal.
- A squealing noise when accelerating in reverse can be an indication of a faulty universal joint in the driveshaft.
- Excessive vibration under acceleration, at highway speed, can also indicate a faulty universal joint.
Front-wheel drive vehicles have gained a loyal following in the last thirty years and are considered very reliable. A front-wheel drive vehicle is also a two-wheel drive vehicle, except that it uses the front wheels to pull the vehicle. Most front-wheel drive vehicles have a transverse engine and transmission, which either requires no differential or uses a differential which is integrated into the transmission. Axles then protrude from either side of the transmission and are splined into the front wheel hubs. These axles are designed with constant velocity (CV) joints on both ends. These CV joints allow the axle the flexibility to adapt to changes in transmission position caused by engine torque and steering actuation. Front-wheel drive systems function very well when used with smaller engines. Four cylinder and six-cylinder engines are very compatible with front-wheel drivelines, as they are not known for producing excessive torque. While there are several more powerful V8 front-wheel drive models being successfully produced, torque steer in these cars can be overwhelming to the driver, as well as creating tire wear and alignment problems. Torque steer occurs under heavy acceleration, when engine torque causes it to flex in the sub-frame.
Carefully inspect these areas before purchasing a front-wheel drive vehicle:
- CV joint dust boots for tears, or leaks.
- A clattering noise when turning sharply to either side and accelerating can indicate a faulty cv-joint/axle.
- Check tires for uneven or accelerated wear patterns.
- Excessive noise when moving the shifter from park and into drive or reverse.