How much do you know about drive axles and differentials?

Study Notes

Rear-wheel-drive vehicles use a live axle to transfer power to the drive wheels, while front-wheel-drive cars use a nonpowered rear axle or final drive assembly.
A drive axle assembly includes ring and pinion gears, a differential, and axle shafts.
The purpose of a drive axle assembly is to change the direction of engine torque and allow the drive wheels to rotate at different speeds.
The final gear reduction in the drive train occurs in the drive axle assembly, and the gear ratio of the final drive is called the axle ratio.
Final drive gear sets may be hunting, nonhunting, or partially nonhunting, depending on the final drive gear ratio.
Open differentials deliver equal torque to both wheels at all times, while limited-slip differentials direct more power to the side gear attached to the wheel with better traction.
When a vehicle travels straight, differential action does not occur, but when it corners, the outside wheel gains the same number of RPMs that the wheel on the inside loses.
Changing the rear end ratio can increase vehicle performance but may lead to decreased fuel economy, incorrect speedometer and odometer readings, increased engine noise, and increased engine wear.
The final drive gear ratio affects final drive gear set manufacture and service, and manufacturers lap the contacting gear teeth to decrease wear.
The position of the drive pinion gear on the ring gear changes during operation, and the gear lubrication must be specifically designed for hypoid gear sets.
Differentials distribute torque to both wheels in a vehicle.
Limited-slip differentials allow for equal or unequal torque distribution.
Preloaded clutches use springs and clutch packs to lock side gears to the case.
Adjustment shims can be used to vary the amount of traction needed for locking.
Cone-type preloading clutch differentials use tapered cones instead of clutch packs.
Viscous-coupled differentials use a silicone-based fluid to resist high-speed differences between shafts.
Eaton "locker" differentials use a unique mechanism to compress clutch packs.
Torsen differentials use a torque sensing, locking design with worm side gears and worm wheel pinions.
Lubricants with friction modifiers are important for clutch discs to prevent premature wear and vibration.
Different manufacturers use different brand names for their differentials such as Positive Traction, Sure-Grip, Anti-Spin, and Traction-Lok.