Heavy-Duty Manual Transmissions and PTOs – Part A

What is the fundamental difference in design between a synchronized constant mesh transmission and the older sliding gear transmission?

Sliding gear transmissions use countershafts, while constant mesh transmissions use a mainshaft. In constant mesh transmissions, the gears are always in mesh with the cluster gears. Sliding gear transmissions use dog teeth, while constant mesh transmissions use shift collars. Constant mesh transmissions rely entirely on the operator to time the shift.

What is the approximate maximum input torque rating, expressed in pound-feet (lb/ft), for the example transmission labeled "RITL O F - 16 7 18 A" by Eaton Fuller?

700 lb/ft 1000 lb/ft 1600 lb/ft 2169 lb/ft

The nomenclature suffix (x) 100 on an Eaton Fuller transmission model number signifies what measurement?

The number of forward gear ratios available. The maximum engine horsepower rating. The nominal torque capacity in lb/ft. The shift pattern ratio split.

A heavy-duty transmission described as an 18-speed, multiple countershaft transmission that uses an autoshift system would be classified as what kind of transmission?

Manual, five-speed, overdrive, synchronized. Autoshift, multiple countershaft. Collar shift, single countershaft, direct drive. Synchronized, triple countershaft, manual shift.

What is the primary function of the transmission in conjunction with the clutch, enabling the vehicle to move from a standstill to highway speed?

To increase the available engine horsepower as road conditions change. To maintain a constant gear ratio that provides maximum torque. To adjust the available engine torque to the changing road and load conditions. To ensure the engine always operates at maximum RPM.

In a heavy transport truck equipped with a five-speed main transmission and a four-speed remote auxiliary transmission, how many total possible forward gear selections are available?

9 15 20 25

A heavy-duty transmission utilizes a five-speed main section and a four-speed auxiliary section. If the first gear in the auxiliary section is used only in low range, how many usable gear ratios does the overall transmission provide?

20 18 15 12

A heavy-duty transmission main section features an overdrive arrangement, such as 0.74:1. This ratio indicates that for every 1.0 rotation of the mainshaft input, the output shaft will rotate:

1.0 revolution (Direct Drive). More than 1.0 revolution (Speed Increase). 0.74 revolutions (Speed Reduction). 1.74 revolutions (Extreme Overdrive).

A multiple countershaft transmission offers the same torque capacity as a single countershaft design but is more compact and requires fewer components. This is achieved because the outward force on each countershaft is reduced to what fraction of the force applied to a single countershaft?

One-quarter One-third One-half Two-thirds

Due to the torque split in a twin countershaft design, the supporting bearings and countershafts can be considerably smaller and lighter because they are required to withstand:

Doubled tooth contact area. Reduced torsional vibration. Smaller forces. Less heat absorption.

What is the most important functional advantage of a twin or triple countershaft transmission design over a single countershaft design?

The path of power is lengthened for efficiency [30a]. Additional gear tooth contact adds strength. The elimination of synchronizers simplifies the assembly [30d]. The gear width is wider for high torque applications.

The heavy-duty transmission assembly receives torque from the engine via the clutch discs, which are splined to which component?

The main drive gear The mainshaft The transmission input shaft The auxiliary drive gear

In a non-synchronized heavy-duty transmission, the input shaft is required to stop rotating when the operator shifts into a starting or reverse gear. What component is responsible for stopping the input shaft?

The detent ball and spring The interlock pin The clutch brake The shift collar

When the clutch brake is applied, how does it stop the input shaft from turning?

The range cylinder pushes air onto the main drive gear. It is squeezed between the release bearing and the input shaft bearing cover. The mainshaft gear floating design arrests rotation. The shift collar locks to the clutch teeth of the input shaft.

What specific feature is included in the input shaft design to eliminate the need for a lip seal in a high-heat and dirty environment?

Roller bearings A windback seal system An O-ring seal system A bronze pilot bushing

In a multiple countershaft transmission, the mainshaft gear is held suspended or "floating" between the countershafts. What component is eliminated due to this floating design?

Thrust washers. Bearings (or bushings/shaft sleeves) between the mainshaft and mainshaft gears. Clutch teeth on the mainshaft gear. Snap rings used to position the washer.

The use of a twin countershaft design allows for the utilization of less expensive straight spur gears in the main section. What required component does this spur gear design help eliminate?

The need for a clutch brake. Thrust control washers. The synchronizer central hub. The reverse idler assembly.

What characteristic of the gear width is allowed in a twin countershaft transmission compared to a single countershaft transmission designed to handle the same torque?

The gear width must be doubled. The gear width must be the same size. The gear width can theoretically be half as wide. The gear width must be helical instead of spur.

Torque is transferred from the engine to the selected mainshaft gear via the countershafts. What is the final step in the main section power path before torque is sent to the auxiliary section?

The mainshaft gear floats away from the countershafts. The output shaft is supported by a large snap ring. It is transferred through the sliding clutch to the mainshaft. The auxiliary drive gear receives the torque split.

What is the primary method used to maintain the proper alignment of the several housings bolted together to form a multiple countershaft transmission assembly?

Shouldered bolts. Tapered plugs. Precise dowelling. Floating cap screws.

What component is used inside the heavy-duty transmission to take up end thrust loads and prevent gears from rubbing on the transmission housing?

Interlock pins Snap rings Thrust washers Shift collars

Thrust washers used in heavy-duty transmissions are available in various thicknesses. What feature assists parts technicians and mechanics in identifying their specific thickness?

Material composition (aluminum or cast iron). Engraved serial numbers. Colour-coating. Internal/external tooth configuration.

In a heavy-duty twin countershaft transmission, how is the rotation of the mainshaft gear accomplished?

The mainshaft gear is splined directly to the mainshaft. The twin countershaft gears rotate the mainshaft gear. The sliding clutch engages the internal splines of the output shaft. The input shaft directly drives the mainshaft gear.

A five-speed main transmission section combined with a three-speed auxiliary transmission provides the operator with how many possible forward gear selections?

9 15 18 20

The auxiliary section of the transmission is designed to provide which three types of gearing combinations?

Direct Drive, Reduction, and Overdrive. Range, splitter, and deep reduction. Twin, Triple, and Single reduction. Block, Pin, and Plate/Disc synchronization.

Which type of gearing in the auxiliary section typically accounts for a large ratio change?

Splitter gearing. Deep reduction gearing. Range gearing Auxiliary reduction gearing.

The auxiliary section of a heavy-duty transmission is generally shifted using what actuation method?

Mechanical linkage. Direct shift levers. Air (pneumatic) signal. Electronic shifting.

The shift linkage required for a heavy-duty compound transmission is typically composed of a mechanical gearshift lever controlling the main section and what other primary component for the auxiliary section control?

A hydraulic system. An air shift system. A complex cable linkage. A secondary floor shift linkage.

If the deep reduction option is selected in a three-speed auxiliary section, the operator gains access to gear selections exclusively within which main section position?

High range only. Overdrive only. Low range only. Direct drive only.

In a four-speed auxiliary section, the operator has the ability to "split" every main section gear while operating in low and high range. What does a "split" (or splitter gearing) provide?

A large ratio change. A small ratio change. Deep reduction. Direct drive (1:1).

When the sliding clutch in a two-speed auxiliary section is moved forward, what operational combination is achieved?

Low range, providing a large reduction. Deep reduction (underdrive). High range, giving a direct drive (1:1). Overdrive, resulting in 0.74:1 ratio.

The main section of a typical twin or triple countershaft heavy-duty transmission is constructed as a:

Synchronized, sliding gear design. Full synchromesh, constant mesh design. Non-synchronized, constant mesh, sliding clutch design. Manual, five-speed, autoshift design.

What is the primary disadvantage of earlier remote auxiliary transmission arrangements compared to modern compound transmissions?

Remote systems were shifted using non-synchronized designs. The shift linkage systems were highly susceptible to wear and damage from falling objects. They could only provide a maximum of 12 usable gears. They were typically positioned 120° apart, causing vibration.

The main purpose of the transmission output shaft is to:

Receive torque from the engine via the clutch. Support the mainshaft gear in a floating design. Deliver torque to the driveline. Provide a mounting position for the speedometer-driven gear.

The output shaft in the auxiliary section is typically supported by which type of bearing?

Needle roller bearings. Tapered roller bearings. Ball bearings. Pilot bushings.

Which type of synchronizer is most popular in heavy-duty truck applications due to its use in larger transmissions, though it is a multi-piece assembly?

Block or Cone type. Pin type Plate and disc type. Constant mesh type.

The synchronizer used for the range shift in the auxiliary section is designed to match the speed of the gear being engaged with the speed of which other component?

The main drive gear. The auxiliary countershaft. The output shaft. The range cylinder piston.

Due to the increasing torque available from modern engines, what type of gearing is now being used in some auxiliary sections, which requires tapered roller bearings to manage the resulting thrust loads?

Spur gearing. Hypoid gearing. Helical gearing Worm gearing.

The air shift system used for the auxiliary section directs air to either side of a piston to move the desired sliding clutch. What component prevents air from passing from one side of the piston to the other, or into the transmission?

Gaskets. O-rings Gaskets and spacers. The yoke assembly.

What is the explicit purpose of the interlock system in a heavy-duty transmission?

To hold the shift rail in the selected position (detent function). To provide resistance when selecting 1st or reverse gear. To prevent the operator from selecting more than one gear at a time. To ensure the clutch brake is engaged before shifting.

The interlock system consists of two metal balls and a pin. When a gear is selected and one shift rail moves, what immediate action does this moving rail initiate in the interlock system?

It forces the ball between the selected rail and the rail beside it to move over and lock the middle rail. It compresses the detent spring, releasing the detent ball. It allows the center rail to move freely. It releases the neutral light switch.

What is the primary function of the spring-loaded plunger used on the first/reverse shift block (lockout device)?

To apply the clutch brake. To lock the shift rail into neutral. To ensure the operator exerts a definite amount of pressure (conscious effort) before selecting 1st or reverse. To disengage the detent ball when shifting forward.

Which shift mechanism component takes the operator's input and moves the sliding clutches to engage the desired mainshaft gear?

The air valve shaft. The shifter cover. The shift rails and forks. The tension spring.

Heavy-duty transmissions typically utilize a shift lever that is a two-piece design. What component, often found at the bottom of the upper lever, reduces the transmission noise transmitted up into the cab?

The spade pin. The tension spring. An isolator The rubber boot.

In a compound transmission, if the auxiliary section is a four-speed, it incorporates a range set of gearing and what other set of gearing?

Deep reduction gearing. Splitter gearing. Underdrive gearing. Overdrive gearing.

What type of heavy-duty transmission is defined as having both the main and auxiliary transmissions contained within a common transmission case?

Auxiliary transmission. Split-torque transmission. Compound transmission Twin countershaft transmission.

The term dog teeth or dog clutch teeth is often used by manufacturers to describe which component in a constant mesh transmission?

The internal splines on the shift collar. The gear teeth on the cluster gear. The fine clutch teeth on the output gear. The blocking ring teeth on a synchronizer.

A multiple countershaft transmission that uses three countershafts is structured such that the engine torque is divided equally between them, and they are positioned how far apart?

180°. 120° apart. 90° apart. 360° apart.