Heavy-Duty Manual Transmissions and PTOs – Part B

What is the primary factor that dictates the service life of bearings, shafts, gears, and thrust washers in a heavy-duty transmission?

The frequency of the torque spikes during gear changes. The maximum load capacity of the transmission housing. The quality of the lubricant used and regularly scheduled lubrication change intervals. The total number of gears utilized in the compound ratio.

When referencing the manufacturer’s recommended lubricant chart, what three criteria must be considered when selecting the appropriate lubricant for a heavy-duty transmission?

Lubricant density, pour point, and heat capacity. Viscosity rating, specific gravity, and contamination level. Type of product, grade (API rating), and viscosity rating (SAE and ISO designation). Core charge, cost, and availability of the synthetic blend.

According to Table 1, which lubricant is specified for use in highly loaded gears and hypoid gear applications?

Heavy-Duty Engine Oil 50 Eaton Approved Synthetic Transmission Oil 50 API - GL5 Automatic Transmission Fluid (ATF)

Based on the manufacturer's recommendations provided in Table 1, what critical warning is given regarding the lubricant selection process?

Always use the highest viscosity available to prevent gear wear. Never use synthetic oils unless the transmission is specifically designed for them. Never mix engine oils and gear oils in the same transmission. Additives and friction modifiers must always be used when operating below −12 °C (10 °F).

The most common lubrication method used on all transmissions is the splash lubrication system. How does this system ensure the upper components, such as the mainshaft and upper countershafts, receive oil?

Oil galleries pump oil directly to the mainshaft assembly. The oil pump sends pressurized oil through internal passages. The countershafts rotate, carrying oil to other countershafts and splashing oil onto the mainshaft assembly. Bolt-on troughs collect oil and deliver it via gravity feed.

To ensure oil is directed to critical internal areas, such as the roller bearing on the reverse idler shaft, the transmission housing often includes what physical feature?

Internal oil pressure passages connected to the main oil pump. Galleries and collection reservoirs cast into the housing. Dedicated external lubrication lines and fittings. Specialized mainshaft gear sleeves with oil holes.

In a heavy-duty transmission, what component is often bolted to the shift bar housing to direct oil thrown from the splashing system to critical areas?

A filter mesh strainer A bolt-on oil trough A magnetic drain plug The shift rail interlock pin

In some transmissions, a pressure type lubrication system is incorporated alongside the splash system. Where is the small eccentric shuttle type oil pump typically located?

In the bottom of the oil reservoir, near the drain plug. Clamped or bolted to the end of the auxiliary countershaft. In the transmission input shaft. Mounted externally on the transmission PTO opening.

What action occurs if the oil cooler lines are plugged on a transmission utilizing an integral oil pump with a relief valve?

The synchronizer assembly automatically disengages. The clutch brake engages to stop the countershaft rotation. The oil will be forced to go over the relief valve, increasing heat rather than getting rid of it. The oil gallery in the mainshaft opens to bypass the pump entirely.

Heavy-duty transmissions that rely on splash lubrication typically filter oil by means of:

An optional filter installed between the pump outlet and the cooler. Magnetic drain plugs or magnets located in the bottom of the transmission case. A mesh strainer located at the output shaft. A pressurized return line leading to a dedicated external filter.

When a pressure pump system is used, what additional component is utilized on the suction tube to assist the magnets in trapping foreign material in the oil?

A secondary magnetic plug A check valve Mesh strainers A bypass filter

If a transmission is not equipped with an internal oil pump, an optional externally mounted pump may be used. Where does this external pump typically receive its oil supply?

From the top of the mainshaft assembly. From the input shaft oil gallery. Through an adapter mounted in the drain plug hole. Directly from the clutch housing reservoir.

What is the definition of an auxiliary drive system, such as a power takeoff (PTO)?

A transfer case component that distributes power to the front and rear axles. A system that transmits power from an engine, transmission, auxiliary transmission, or transfer case to equipment requiring rotating power. A specialized hydraulic pump mounted on the crankshaft. A driveline stabilizer that reduces torsional vibration.

Which types of auxiliary drive systems are always driving whenever the engine is turning?

Transmission-mounted power takeoff and transfer case mounted PTO. Drop box and auxiliary transmission mounted PTO. Front engine mounted and rear engine mounted auxiliary drives. Cable actuated and electrically actuated PTOs.

What is the disadvantage of a rear engine-mounted auxiliary drive connected to the flywheel housing?

It requires complex cable actuation to engage. It is always driving whenever the engine is running. It requires the use of helical gears to handle the torque. It can only be used with multiple countershaft transmissions.

A power tower auxiliary drive unit is commonly used on oilfield trucks to drive heavy-duty winches. To what component is this unit typically bolted?

The main transmission input shaft. The top of the twin countershaft auxiliary transmission. The rear PTO adapter housing. The differential carrier assembly.

What enables the operator to vary the speed and torque output of an auxiliary transmission top-mounted power takeoff (power tower)?

The ability to use the range cylinder to select high or low range. Shifting the main transmission through its gears while the auxiliary transmission is put in neutral. Changing the ratio of the output shaft gears via an external switch. Engaging the clutch brake to reduce the countershaft speed.

Auxiliary PTO bolt-on units are available in two specific mounting configurations. What are they?

4-bolt or 6-bolt mounted. 6-bolt or 8-bolt mounted. Single-speed or multiple-speed mounted. Top-mounted or bottom-mounted.

A drop box differs from a transfer case in its primary function because the drop box:

Always provides a large ratio change (reduction). Drives some auxiliary function rather than another drive axle. Is mounted to the front of the crankshaft. Requires the use of hydraulic actuation.

Which accessory drive system is used when large amounts of torque are required, and the main transmission must be in a gear to deliver the necessary speed and torque?

Rear engine-mounted drive. Front engine-mounted hydraulic pump. Power takeoff (PTO) output shaft on a transfer case. Electric solenoid actuated PTO.

PTO output drive shafts constructed of tubular material are designed specifically for which applications?

Low torque or low speed applications. High torque or rpm applications. Clutch shift actuated systems only. Systems requiring only solid round shafting.

The power flow through a PTO may include one to three gears before driving the output shaft. What is the consequence each time a gear is added to the PTO power flow?

The torque output is reduced. The speed of rotation is increased. The direction of rotation is reversed. The gear clash risk is increased.

What critical safety step must the operator ensure before engaging a power takeoff unit?

That the vehicle speed is below 5 mph. That the PTO indicator light is illuminated. That the clutch is disengaged and the transmission gears are not turning. That the shift rail is locked by the interlock pin.

Engaging the PTO while the transmission gears are still turning will result in:

Increased stress on the driveline shaft. The clutch shift friction disks overheating. Gear clashing and damage to the engaging teeth. Activation of the torque-limiting clutch brake.

The cable actuated PTO system is essentially what type of mechanism?

Hydraulic pressure application system. Rotary motion solenoid system. A push-pull type of activation system. A mechanical linkage and control rod system.

On heavy trucks equipped with compressed air for the braking system, the PTO may be activated using air to move which specific component?

The solenoid. The Air Shift Cylinder. The shift rod and fork assembly. The engagement switch indicator light.

What is the primary functional advantage of a Clutch Shift Actuated PTO (also called power shift or hot shift)?

It uses simpler sliding gears, reducing cost. It may be safely engaged and disengaged with the vehicle in motion. It requires less lubrication than a sliding gear PTO. It uses a normally closed indicator switch for operation.

How do Clutch Shift PTOs achieve engagement, unlike traditional PTOs that use sliding gears?

Through mechanical linkage and detent balls. By electrical solenoid operation controlled by the dash switch. By means of friction disks, much like those used in automatic transmissions. By utilizing a fluid coupling device.

The Indicator Switch used in most PTO systems serves what purpose?

To control the electric solenoid that moves the shift rod. To interrupt the power flow if the transmission speed is too high. To let the operator know whether the PTO is in the engaged position. To manually open the oil relief valve.

When a single gear adapter housing is sold to a customer to facilitate PTO installation due to obstructions, what critical functional change must the parts technician remind the customer about?

The need for four gaskets to prevent leaks. The requirement for a filler block instead of an adapter plate. A single gear adapter will change the rotation of the output shaft. The adapter housing eliminates the need for backlash adjustment.

Power takeoffs generally receive lubrication from the major component to which they are attached. What is the procedural consequence once the PTO is installed?

The PTO should be filled with synthetic gear oil before operation. The major component requires an additional amount of lubricant. The PTO must be filled with engine oil to prevent seal damage. The oil trough bolted to the shift bar housing must be removed.

The gasket installed between the PTO and the transmission provides which two essential functions?

It acts as a friction disk and adjusts gear speed. It prevents wear between the mating surfaces and absorbs vibration. It acts as a seal to keep lubrication from leaking and provides a way of setting the proper backlash. It supports the driveline yoke and reduces gear noise.

What is the maximum number of gaskets recommended to be installed between the PTO and the transmission mounting surfaces?

Two Three Four Six

If more than four gaskets are required to achieve the proper backlash during PTO installation, what replacement component must be used instead?

A six-bolt PTO adapter plate. A special filler block. A clutch shift actuated PTO. A new main transmission housing.

The process of setting the proper backlash using selective thickness gaskets is necessary to provide what feature in the meshing gears?

Alignment Lubrication flow Clearance between the teeth required for heat expansion. Torsional dampening

To adapt a six-bolt PTO to an eight-bolt opening so that it may be installed in a different location, what component is required?

A special filler block. An auxiliary oil pump assembly. An adapter plate. A seven-speed auxiliary transmission.

When an adapter plate is used to mount a PTO, how many gaskets are required at minimum?

None, because the adapter plate includes an integrated seal. One gasket between the PTO and the transmission. At least one gasket between the PTO and the plate and one between the plate and the transmission. Four gaskets total to ensure adequate sealing.

When a transmission is opened for repair, what essential maintenance consideration should a parts technician remind a customer about, regarding low-cost components that ensure a trouble-free repair?

Upgrading to a clutch shift PTO. Replacing only the damaged shafts or gears. Replacing bearings, O-rings, seals, and gaskets. Installing a mesh strainer on the input shaft.

If a customer is replacing a failed transmission shaft, which related sales items should the technician recommend, according to Table 2?

Only the gears and clutch assembly. Lubrication hoses and air line fittings. Gears, bearings/bushings, spacers/thrust washers (selective), seals, gaskets, and lubricant. Only the PTO U-joint and steady bearing.

Which specific components in the list of common PTO replacement parts require special care and attention because they are susceptible to wear and leakage?

Driveline U-joints. O-rings and seals (especially output shaft). PTO gears and bearings. Clutch shift friction disks.

Why must a parts technician provide the model number from the PTO tag when ordering replacement parts for a PTO assembly?

The PTO model number dictates the mounting bolt pattern (6 or 8 bolt). PTOs are specialty items and parts are not readily available, requiring specific supplier identification. The model number determines whether the PTO is cable or air actuated. The model number indicates the required fluid viscosity rating.

What type of PTO output shaft material is used in standard applications not requiring extremely high torque or RPM?

Tubular material Solid round, square or hexagon material Ceramic material Multi-disc friction material

In the context of core management for remanufactured transmissions, if a customer returns a core that requires tear down and inspection, what must the parts technician provide?

An immediate credit equivalent to a "clean core." An invoice for the core inspection fee. A receipt, followed by a credit once the inspection is completed. A mandatory new transmission overhaul kit.

What is the fundamental purpose of the core charge system used for remanufactured components?

To ensure the customer pays the full cost upfront. To maintain accurate inventory records of new transmissions. To encourage the customer to return a rebuildable core. To cover the cost of the magnetic drain plug replacements.

When the transmission uses the pressure type lubrication system, the oil is typically supplied to the pump via which component?

The main bearing retainer. A trough cast into the inside of the transmission housing. An external hose connected to the engine oil system. The auxiliary drive output shaft.

What type of lubricant is typically recommended for use in transmissions when the ambient temperature is below −12 °C (10 °F), according to Table 1?

Heavy-Duty Engine Oil 50 Heavy-Duty Engine Oil 30 or API MT-1 75W Automotive Gear Oil 80-90 Eaton Approved Synthetic Transmission Oil 50