# Automobile Engineering Questions and Answers – Universal Joints and Differential

This set of Basic Automobile Engineering Questions and Answers focuses on “Universal Joints and Differential”.

1. Which types of joints are used when the shafts are inclined?
a) Universal joint
b) Hinge joint
c) Ball and socket joint
d) Pivot joint

Explanation: Universal joint is used when the shafts are inclined and intersecting. It is very compact in design and simple in construction. It is very effective at small angles of propeller shaft movement.

2. The axes of the two shafts are intersecting and are at 25° to each other. These two shafts are connected by Hook’s joint. At which position of the drives shaft velocity ratio will be maximum?
a) 90°, 270°
b) 0°, 180°
c) 180°, 270°
d) 90°, 180°

Explanation: (ωB / ωA) = (cos α) / (1 – cos2θ sin2α) where A = driving shaft and B = driven shaft and α is the angle between shaft A and shaft B. θ is the angle through which the shaft A rotates. Velocity ratio is maximum when θ = nπ where n = 1, 2, 3, …… i.e. θ = θ° or 180°.

3. Which of the following is the disadvantage of the open differential?
a) High in cost
b) Not reliable
c) Complex design
d) Sends most of the power to the wheel having less traction

Explanation: The major disadvantage of the open differential in that it transfers the power to the wheel even if it is on a slippery road. That’s why it is not used in off driving cars.

4. Why do the hypoid gears require special lubricant?
a) Teeth are soft
b) Teeth are hard
c) Gears run faster
d) There is relative motion between teeth

Explanation: Hypoid gears require special lubricant because of the extreme pressure between the teeth. The sliding motion of the teeth is effective due to the use of special lubricant.

5. The axes of the two shafts are intersecting and are at 30° to each other. These two shafts are connected by Hook’s joint. At which position of the drives shaft velocity ratio will be minimum?
a) 90°, 270°
b) 0°, 180°
c) 180°, 270°
d) 90°, 180°

Explanation: (ωB / ωA) = (cos α) / (1 – cos2θ sin2α) where A = driving shaft and B = driven shaft and α is the angle between shaft A and shaft B. θ is the angle through which the shaft A rotates. Velocity ratio is minimum when θ = m&pi/2 where m = 1, 3, 5, …… i.e. θ = 90° or 270°.
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6. Where is the differential located?
a) Between transmission and rear axle
b) Between engine and transmission
c) Between two propeller shaft
d) Between steering wheel and steering column

Explanation: The differential used to incorporate the speed of the rear wheels and front wheels during turning. It is located between the transmission and rear axle.

7. The axes of the two shafts are intersecting and are at 35° to each other. These two shafts are connected by Hook’s joint. At which position of the drives shaft velocity ratio will not be unity?
a) 42.145°
b) 222.145°
c) 317.85°
d) 141.52°

Explanation: (ωB / ωA) = (cos α) / (1 – cos2θ sin2α) where A = driving shaft and B = driven shaft and α is the angle between shaft A and shaft B. θ is the angle through which the shaft A rotates. Velocity ratio is unity when tanθ = ± $$\sqrt{cos\alpha} = ± \sqrt{cos35}$$ = ± 0.90 i.e. θ = 42.145°, 222.145°, 317.85°, and 137.85°.

8. What is the need of the universal joint?
a) To change inclination
b) To bend sideways
c) To transfer torque at an angle
d) To change length

Explanation: The universal joint transfers the torque to two intersecting shafts. One or two universal joints are used depending upon the type of rear-drive used.

9. The axes of the two shafts are intersecting and are at 35° to each other. These two shafts are connected by Hook’s joint. At which position of the drives shaft acceleration will be maximum?
a) 68.4°
b) 96.1°
c) 225.5°
d) 330.7°

Explanation: (ωB / ωA) = (cos α) / (1 – cos2θ sin2α) where A = driving shaft and B = driven shaft and α is the angle between shaft A and shaft B. θ is the angle through which the shaft A rotates. Acceleration will be maximum when cos2θ = (2 sin2α) / (2 – sin2α) =(2 sin240°) / (2 – sin240°) = 0.5207 i.e. 2θ = 58.62 i.e. θ = 29.31°, 180° – 29.31° = 150.69°, 180° + 29.31° = 209.31°, 360° – 29.31° = 330.69°

10. A two-piece propeller shaft requires one universal joint.
a) True
b) False

Explanation: A two-piece propeller shaft requires a center support bearing. If there is a large wheelbase, the long propeller shaft is needed. So a two-piece propeller shaft is used in such case with a center support bearing. By incorporating this there is no sag or whirl.

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