303E

Question 1

Identify four (4) of the major hydraulic retarder components

Answer 1

a) retarder rotor (rotating assembly)
b) retarder housing (stator)
c) oil pump and oil supply circuit
d) oil cooler (heat exchanger)
e) retarder control valve and control circuit

Question 2

Explain the purpose of the hydraulic retarder rotor.

Answer 2

The retarder rotor is the rotating member of the hydraulic retarder. It is attached to a
powertrain member output. As the rotor vanes strike the oil in the retarder housing,
resistance occurs. That drag is transmitted to the driveline, thereby slowing the
vehicle.

Question 3

Explain the purpose of the retarder/stator housing.

Answer 3

The retarder housing encloses the retarder rotor and contains the oil supplied during
retarder operation. The close clearance between the rotor and the housing causes the
rotor to drag as it passes through the oil. This drag slows the vehicle. A great deal of
heat occurs due to this reaction.

Question 4

Explain the purpose of the oil cooler used in the hydraulic retarder system.

Answer 4

The cooler helps maintain the oil temperature within safe limits.

Question 5

The only type of oil cooler used in the hydraulic retarder system is the oil-to-air
design.
t/f

Answer 5

false;

Question 6

Identify the three (3) possible locations where hydraulic retarders could be
positioned.

Answer 6

a) between the torque converter and transmission
b) on the transmission output shaft
c) on the driveline

Question 7

Explain the basic operation of a hydraulic retarder.

Answer 7

The operator moves a mode selector switch or lever in order to activate the hydraulic
retarder.

Question 8

The hydraulic retarder changes the heat energy created by the vehicle moving over
the road into kinetic energy.
a) true
b) false

Answer 8

false;

Question 9

The hydraulic retarder operates on the basis of a change in fluid friction.

a) true
b) false

Answer 9

true

Question 10

What is the stationary member in a retarder?

Answer 10

Retarder/stator housing

Question 11

The position of the hand air valve controls the amount of air pressure applied. An increase in air pressure to the retarder hydraulic valve causes

Answer 11

A higher pressure of oil inside the retarder, due to centrifugal force of oil thrown out by the rotor, increasing braking force

Question 12

When a retarder is installed between engine and torque converter what is required?

Answer 12

A lockup clutch inside torque converter

Question 13

When retarder is applied the lockup clutch engages putting the torque converter in what state?

Answer 13

Direct drive

Question 14

What force over comes the spring pressure in the retarder control valve

Answer 14

Air pressure

Question 15

What force counter acts the air pressure in the retarder control valve?

Answer 15

Oil pressure plus spring pressure

Question 16

When hydraulic retarder troubleshooting, after an external inspection, what must also be done?

Answer 16

Pull the magnetic drain plug and filter element. Look for shiny steel particles, aluminum particles, rubber particles or iron and steel chips

Question 17

What are the possible different sources of oil for a hydraulic retarder

Answer 17

It’s own tank, engine, transmission and or the torque converter

Question 18

The retarder is most efficient when it is connected directly to what?

Answer 18

The driveshaft.

Question 19

In a powershift transmission what is the best way to connect a retarder to the driveshaft?

Answer 19

With a lock up clutch

Question 20

The biggest concern in any hydraulic retarder is what?

Answer 20

The heat rise. Electronic controlled hydraulic retarder’s have many inputs and outputs to run the retarder as efficiently as possible, and to warn of high temp

Question 21

A hydraulic retarder works on the ____ instead of the wheels.

Answer 21

Driveline

Question 22

In addition to the service brakes, the optional hydraulic retarder provides assistance with ____ the machine.

Answer 22

Slowing

Question 23

True or False

The oil pump that supplies oil to the torque converter and transmission may also be used to supply oil to the hydraulic retarder?

Answer 23

True

Question 24

Separate oil pump, reservoirs, oil coolers, and oil supply or return circuits may be used when retarder’s are mounted where?

Answer 24

Transmission output shaft or on the driveline

Question 25

True or False

Oil-to-coolant type oil coolers are the only
Oil coolers used with torque converter/retarder oil circuits?

Answer 25

False

Question 26

What are three methods of controlling a retarder?

Answer 26

Manual operator control

Air over hydraulic control

Electronic control

Question 27

Where is an input hydraulic retarded located in relation to the transmission?

Answer 27

In front of the transmission.

Question 28

Output hydraulic retarded are located on the output of the engine. (T/F)

Answer 28

False

Question 29

A hydraulic retarded maybe used ad a supplementary park brake. (T/F)

Answer 29

False.