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ASE P2 Test Preparation Guide: Drivetrain

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Sample Review Questions:
1. Counterman A says constant velocity joints are used on front-wheel drive cars and also some rear-wheel and all-wheel drive cars.   Counterman B says a worn outer CV joint often makes a clicking or popping noise when turning. Who is right?
a. Counterman A only
b. Counterman B only
c. Both Counterman A and B
d. Neither one

2. Counterman A says U-joints can cause driveline vibrations if the operating angle is too great. Counterman B says U-joints must always be replaced in pairs. Who is right?
a. Counterman A only
b. Counterman B only
c. Both Counterman A and B
d. Neither one

3. Counterman A says a replacement halfshaft must have the same length and number of shaft splines as the original.   Counterman B says some vehicles like Honda and Chrysler minivans may use any one of several different halfshaft assemblies.   Who is right?
a. Counterman A only
b. Counterman B only
c. Both Counterman A and B
d. Neither one

4. All of the following statements about sealed wheel bearing and hub assemblies are true except:
a. They cannot be disassembled or lubricated
b. Some contain an integral wheel speed sensor for the ABS system
c. They can be adjusted to reduce play and wheel runout
d. They may make a chirping or growling noise if the bearing is bad

ANSWER KEY
1C, 2A, 3C, 4C

EXPLANATIONS:
1. Constant Velocity (CV) joints are used on the ends of driveshafts in front-wheel drive (FWD) cars and minivans. CV joints may also be used on driveshafts in some rear-wheel drive (RWD) cars, and also all-wheel drive (AWD) cars and four-wheel drive (4WD) trucks. CV joints maintain a constant speed across the joint as the joint angle changes. This eliminates vibrations in the driveline. CV joints are packed with special grease, and are sealed inside a protective rubber or plastic outer boot. Boot damage can allow loss of grease and joint contamination with dirt, leading to joint failure. Typical symptom of a failing outer CV joint is a clicking or popping noise when turning.

2. U-Joints are flexible couplings used primarily on RWD driveshafts. A U-joint has a double yoke and four-point center cross with needle bearing cups. The geometry of the joint allows the angle of the shaft to change, but also causes cyclic vibrations if the angle is too great (more than a few degrees off-center). Play in a worn U-joint may cause a vibration at any speed or angle, or make chirping noises, or produce a clunk when an automatic transmission is put into gear. A worn U-joint should be replaced, but there is no need to replace both U-joints on a driveshaft unless both are high-mileage or have excessive play.

3. FWD cars and minivans have two short driveshafts called “halfshafts” that connect the transaxle to the front wheels. Each shaft has an inner and outer CV joint. Right and left side shafts may be equal lengths or different lengths. Shafts are usually replaced as complete assemblies because it is faster and easier than rebuilding the old shaft. Some car makers (Honda and Chrysler) may use a variety of different shafts in the same vehicle (different shaft lengths, spline diameters and/or number of teeth).

4. The wheel bearings on most late model cars are sealed assemblies that mount on the hub. They are lubed for life and require no adjustments. In fact, there are no adjustments and no way to disassemble, clean or lubricate the bearings. Some also have a built-in wheel speed sensor (WSS) for the antilock brake system. If the bearing is making noise or has play, or the WSS is bad, the hub unit has to be replaced.

 

Sections covered:

Automatic Transmission

Batteries

Brakes

Cooling System

Drivetrain

Emissions

Engine Mechanical Parts

Exhaust

Fuel System

HVAC

Gaskets

Ignition System

Manual Transmission

Suspension and Steering

Management

 

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