Eaton Fuller 18-Speed Manual Transmission

Quick Facts

Manufacturer: Eaton
Transmission Family: Eaton Fuller Roadranger RT-18 Series
Transmission Type: Heavy-Duty Non-Synchronized Range-Splitter Manual Transmission
Forward Speeds: 18
Reverse Speeds: 4
Basic Design: Five-speed main section with low and high ranges plus a two-speed splitter
Common Models: RTLO-14918B, RTLO-16918B, RTLO-18918B, RTLO-20918B, RTLO-22918B, and related configurations
Maximum Input Torque: Up to 2,250 lb-ft depending on model
Maximum Gross Combination Weight: Eaton lists the RT-18 family for unlimited GCW within approved application requirements
Top-Gear Configuration: Overdrive
Clutch Type: Driver-Operated Heavy-Duty Dry Clutch
Shift Control: Floor-Mounted Shift Lever with Range Selector and Splitter Button
Synchronization: Non-Synchronized Main Gearing with air-operated range and splitter systems
Common Oil Capacity: Approximately 28 pints or 13 liters depending on model
Approximate Length: Approximately 33.1 inches on common RTLO configurations
Approximate Weight: Generally around 710–730 lbs depending on model and installed equipment
PTO Compatibility: Available PTO openings for approved vocational equipment
Primary Applications: Heavy Haul, Oversized Freight, Logging, Mining, Construction, Oilfield, Agriculture, Long Haul, and Specialized Transportation
Common Truck Class: Class 8
Production Status: Model availability varies; Eaton has discontinued certain RTLO configurations while continuing RT-18 parts, service, remanufacturing, and technical support

Overview

The Eaton Fuller 18-Speed Manual is one of the most capable and versatile manual transmissions used in North American commercial trucking. It is designed for operations requiring close gear spacing, deep starting reduction, high torque capacity, and precise driver control.

Unlike a 13-speed, which normally splits only its upper-range gears, the 18-speed allows the driver to split both the low-range and high-range gear positions. This provides eighteen progressive forward ratios and four reverse ratios.

The large number of available ratios helps the driver keep the engine within its productive rpm range while pulling heavy loads, climbing steep grades, operating at low speeds, or traveling through changing terrain.

The transmission is especially associated with heavy-haul trucks, logging trucks, oilfield equipment, oversized-load tractors, construction trucks, and other vocational trucks. It is also used in highway tractors whose owners want maximum control over engine speed and gear selection.

The Eaton Fuller 18-speed requires more driver knowledge than a conventional 10-speed or 13-speed. However, not every ratio must be used during every acceleration. Drivers select the ratios appropriate for the load, terrain, road speed, and operating conditions.

Key Characteristics

The defining characteristic of the Eaton Fuller 18-speed is its ability to split the gear positions in both low and high ranges.

The transmission uses a five-speed main section combined with a two-range and two-speed auxiliary section. The splitter provides direct and overdrive selections within the gear positions.

One low-position ratio is primarily used as a starting ratio. The remaining main-section positions are used in low range and then repeated in high range.

The transmission provides smaller ratio steps than a conventional 10-speed. This helps drivers maintain engine rpm while accelerating heavy combinations or climbing grades.

The Eaton Fuller twin-countershaft design divides engine torque between two countershafts. This distributes internal loading and provides a strong torque-to-weight ratio.

The main transmission is non-synchronized. Drivers must match engine speed, transmission speed, and road speed before engaging the next gear.

The range and splitter systems are operated by compressed air. Proper vehicle air pressure is required for dependable auxiliary-section operation.

The transmission’s deep starting ratios help move heavily loaded combinations without excessive clutch slipping. Its upper overdrive ratios support highway operation after the truck reaches cruising speed.

How the Transmission Works

Engine power passes through the clutch into the transmission input shaft. Internal gearing changes the relationship between engine speed and output-shaft speed before delivering power to the driveshaft, differentials, axles, and wheels.

The transmission’s eighteen forward ratios come from a five-speed main section and a two-by-two auxiliary section containing low and high ranges plus direct and overdrive splitter selections.

A typical shift progression is:

Low Direct
Low Overdrive
First Direct
First Overdrive
Second Direct
Second Overdrive
Third Direct
Third Overdrive
Fourth Direct
Fourth Overdrive
Fifth Direct
Fifth Overdrive
Sixth Direct
Sixth Overdrive
Seventh Direct
Seventh Overdrive
Eighth Direct
Eighth Overdrive

The exact labeling and shift pattern should be confirmed using the transmission’s shift knob and Eaton instructions.

The driver uses the main shift lever to select the main-section gear position. The range selector changes between low and high ranges. The splitter button selects the direct or overdrive side of the chosen gear position.

Lever Shifts

A lever shift occurs when the driver physically moves the shift lever into another main-section position.

Because the main transmission is non-synchronized, the driver must match engine speed with the selected gear. Eaton traditionally teaches double-clutching during lever shifts.

Split Shifts

A split shift changes from direct to overdrive or from overdrive to direct while the main shift lever remains in the same position.

The driver preselects the splitter and briefly releases engine torque. The auxiliary section completes the shift when the internal speeds match.

Compound Shifts

A compound shift combines movement of the main shift lever with a change in splitter position.

For example, the driver may move from one gear’s overdrive split into the next gear’s direct split. Proper timing is necessary so both changes occur smoothly.

Range Shifts

The driver preselects high range before leaving the final low-range gear. The range change occurs as the main shift lever passes through neutral.

When downshifting from high range into low range, the driver preselects low range before moving the lever through neutral.

Reverse Operation

The splitter provides additional reverse-ratio choices, producing four reverse speeds on common Eaton Fuller 18-speed configurations.

Range shifts should not be attempted while the truck is moving in reverse.

Common Specifications

Transmission Type

The Eaton Fuller 18-speed is a heavy-duty, constant-mesh, non-synchronized manual transmission with air-operated range and splitter controls.

Forward Speeds

The transmission provides eighteen forward ratios.

Both the low-range and high-range gear positions can be split into direct and overdrive ratios.

Reverse Speeds

The transmission commonly provides four reverse ratios.

Multiple reverse ratios can help operators match backing speed to the load, terrain, and maneuvering requirements.

Maximum Torque Capacity

RT-18 models are available in several torque ratings. Depending on the model, input-torque capacity can range from approximately 1,450 to 2,250 lb-ft.

The transmission model must be matched to the engine’s maximum programmed torque.

Gross Combination Weight

Eaton lists the RT-18 family with unlimited maximum GCW.

This does not mean the truck has unlimited legal or mechanical capacity. The complete vehicle remains limited by its engine, clutch, frame, driveshaft, axles, suspension, tires, wheels, brakes, permits, and approved application.

Gear Configuration

The transmission uses a five-speed main section and a two-by-two auxiliary section.

The auxiliary section contains low and high ranges plus direct and overdrive splitter ratios.

Overall Ratio Coverage

The 18-speed provides broad overall ratio coverage, combining deep starting reduction with closely spaced intermediate gears and an overdrive highway ratio.

Exact ratio coverage depends on the model and ratio set.

Gear Ratios

Gear ratios differ between RTLO models. The complete transmission model number should be used to identify the starting ratio, intermediate ratios, top-gear ratio, and reverse ratios.

Overdrive Top Gear

Most common RTLO 18-speed models use an overdrive top gear. This reduces engine rpm during highway operation when paired with an appropriate rear-axle ratio and tire size.

Range System

The range selector changes the transmission between low and high ranges.

The desired range is preselected before the shift lever passes through neutral. Compressed air then completes the range change.

Splitter System

The splitter provides direct and overdrive selections within both low and high ranges.

The split shift occurs after the driver preselects the ratio and briefly removes torque from the transmission.

Clutch System

The transmission normally operates with a heavy-duty dry clutch controlled by a clutch pedal.

Clutch actuation may be mechanical, hydraulic, or power-assisted depending on the truck and model year.

Clutch Brake

The clutch brake stops or slows the transmission input gearing when the truck is stationary, allowing the driver to engage a starting gear or transmission-driven PTO.

The clutch brake should not be used during normal moving shifts.

Shift Controls

A typical shift knob includes:

Main gearshift lever
Low- and high-range selector
Direct and overdrive splitter button
Shift-pattern identification

The exact control arrangement should be verified for the individual transmission.

Lubrication System

The transmission requires an Eaton-approved manual transmission lubricant.

Certain configurations use an integral oil pump or external cooler to support high-load and severe-duty operation.

Oil Capacity

Common RTLO configurations use approximately 28 pints or 13 liters of lubricant. The exact capacity should be confirmed using the model number and current Eaton service information.

Transmission Length

Common RTLO configurations are approximately 33.1 inches long. Shift-housing position, input shaft, output equipment, and other options can affect overall dimensions.

Transmission Weight

Many Eaton Fuller 18-speed configurations weigh approximately 710 to 730 pounds without the clutch and certain installation components.

PTO Compatibility

PTO openings may support hydraulic pumps, wet kits, winches, compressors, blowers, dump bodies, cranes, tank equipment, and other vocational systems.

The PTO must match the transmission model, mounting opening, speed, rotation, torque requirement, lubrication needs, and duty cycle. Additional information is available in PTO System Explained.

Installation Requirements

Installation must account for engine torque, clutch capacity, flywheel housing, input shaft, driveshaft angles, rear-axle gearing, tire size, PTO requirements, transmission cooling, frame clearance, and complete-vehicle application approval.

Common Applications

Extreme heavy-haul transportation
Oversized-load transportation
Multi-axle heavy-haul tractors
Logging and forestry operations
Mining operations
Oilfield transportation
Construction equipment hauling
Lowboy and RGN operations
Agricultural equipment hauling
Mountain-route transportation
Specialized machinery hauling
Crane and rigging operations
Bulk and pneumatic transportation
Tanker operations
High-gross-weight combinations
Off-highway vocational work
Long-haul owner-operator tractors
Severe-duty vocational trucks

Truck and Engine Compatibility

The Eaton Fuller 18-speed has been offered in heavy-duty trucks from Peterbilt, Kenworth, Western Star, Freightliner, International, Mack, Volvo, Sterling, and other manufacturers.

It is most commonly associated with truck configurations requiring high engine torque, deep starting reduction, close ratio spacing, PTO compatibility, or precise low-speed control.

Common truck platforms include the Peterbilt 389, Peterbilt 567, Kenworth W900, Kenworth T800, Kenworth T880, and Kenworth C500.

Other compatible platforms include the Freightliner Classic, Freightliner Coronado, Freightliner 122SD, Western Star 4900, Western Star 6900XD, and Volvo VNX.

Common engine pairings include the Cummins X15, Cummins ISX15, Cummins N14, Caterpillar 3406, Caterpillar C15, Detroit Series 60, Detroit DD16, and other high-torque heavy-duty diesel engines.

The transmission’s approved input-torque rating must equal or exceed the engine’s maximum programmed torque. Engine modifications or higher electronic torque settings can overload a transmission that was suitable for the engine’s original factory calibration.

The rear-axle ratio must be selected with the transmission’s starting ratio and overdrive top gear in mind. Improper gearing can cause excessive clutch use, poor starting performance, driveline stress, low engine rpm, or unnecessarily high cruising rpm.

Advantages

Eighteen forward ratios provide maximum operating flexibility
Both low- and high-range gears can be split
Deep starting reduction helps move heavy loads
Close ratio spacing helps maintain engine rpm
Strong fit for extreme heavy-haul applications
Useful on steep grades and mountain routes
Provides excellent low-speed control
Four reverse ratios improve backing flexibility
Available in high-torque configurations
Maximum rating reaches approximately 2,250 lb-ft
Twin-countershaft design distributes internal loading
Suitable for logging, mining, and oilfield applications
Provides direct driver control over power delivery
Can support transmission-mounted PTO equipment
Strong parts and service familiarity
Widely respected among experienced heavy-haul drivers
Can skip unnecessary ratios when lightly loaded
Broad used and remanufactured availability

Limitations or Considerations

Requires substantial driver training
More complicated shift pattern than a 10-speed or 13-speed
Driver must coordinate the clutch, lever, range selector, and splitter
Non-synchronized design requires accurate rpm matching
Not every driver needs eighteen ratios
Manual clutch operation can cause fatigue in traffic
Driver technique strongly affects transmission life
Range and splitter systems depend on adequate air pressure
Air leaks can interrupt auxiliary shifts
Improper splitter use can cause delayed or harsh shifting
Incorrect shifting can damage gears and engagement teeth
Clutch replacement adds maintenance expense
Heavy-duty configurations may require transmission cooling
High-torque engines can exceed lower-rated models
Some transmission models have been discontinued
Manual transmissions are less common in newer fleet tractors
Low-speed maneuvering requires careful clutch control

Driver and Operator Experience

The Eaton Fuller 18-speed gives the driver extensive control over the truck’s engine speed and power delivery.

The driver can use every ratio when moving an extremely heavy combination or skip selected ratios when the truck is lightly loaded. The goal is to use the ratios that maintain smooth acceleration without unnecessary shifting.

Learning the 18-speed requires understanding the difference between the range selector and the splitter.

The range selector changes the transmission between low and high ranges. The splitter divides each gear position into direct and overdrive ratios.

During a split shift, the driver leaves the main shift lever in the same position, moves the splitter button, and briefly releases torque. During a compound shift, the driver moves the lever and changes the splitter position together.

The close ratios help reduce the amount of engine-speed change between gears. This is especially valuable when a heavy truck is climbing a grade and cannot afford a large loss of momentum.

The transmission can also improve descending control because the driver has more ratio choices available for matching road speed, engine braking, and terrain.

Drivers should select an appropriate starting gear based on weight, grade, and surface conditions. Starting in too high a gear can overheat the clutch. Starting unnecessarily low may add extra shifts without improving performance.

The clutch brake should be used only when the truck is stationary or nearly stopped. Pressing the clutch pedal fully against the clutch brake during moving shifts can cause damage.

Maintenance and Ownership Notes

Transmission lubricant should be checked at the recommended interval and whenever a leak is suspected.

Only an Eaton-approved lubricant of the proper viscosity should be used. Incorrect lubricant can affect shifting, operating temperature, seal life, bearing life, and gear protection.

Oil leaks commonly develop around the input seal, output seal, PTO openings, shift-bar housing, auxiliary case, range cylinder, splitter cylinder, and case joints.

The range and splitter air systems should be inspected for damaged hoses, loose fittings, contaminated valves, worn seals, and air leakage.

Normal truck air pressure must be available before the auxiliary section can function correctly. Poor splitter or range operation may originate elsewhere in the vehicle’s air system.

The clutch and clutch brake must be adjusted and maintained correctly. A dragging clutch can cause gear clash and difficult initial engagement.

The shift knob, control valve, gearshift lever, tower, bushings, and isolator should be inspected when the controls become loose or inconsistent.

Driveshaft balance, universal joints, carrier bearings, driveline angles, engine mounts, and transmission mounts can affect transmission life and shift quality.

High-gross-weight, mountain, and severe-duty operations may require closer monitoring of lubricant temperature and condition. Some configurations use an oil pump or external cooler.

The model and serial numbers should be recorded from the transmission identification tag before ordering parts or replacement units.

Common Transmission Problems

Gear Grinding

Grinding commonly results from incorrect engine-speed matching. It may also indicate a dragging clutch, worn engagement teeth, damaged sliding clutches, shift-linkage problems, or improper clutch-brake use.

Splitter Will Not Shift

A splitter that remains in one position may have low air pressure, an air leak, damaged lines, a defective control valve, a worn splitter cylinder, contaminated air components, or internal auxiliary-section damage.

Delayed Split Shift

A split shift may be delayed when the driver does not release driveline torque.

Mechanical causes include restricted air flow, leaking seals, sticking valves, worn splitter components, or internal damage.

Range Will Not Change

Failure to shift between low and high ranges can result from low air pressure, leaking air lines, a faulty selector valve, a worn range cylinder, contaminated components, or auxiliary-section wear.

Transmission Jumps Out of Gear

Possible causes include worn engagement components, damaged gear teeth, excessive shaft movement, bearing wear, bent shift components, or incomplete gear engagement.

Clutch Drag

A clutch that does not release completely can make starting-gear engagement and moving shifts difficult.

Possible causes include improper adjustment, linkage problems, hydraulic faults, warped clutch components, or damaged release hardware.

Clutch Brake Wear

A worn clutch brake can make it difficult to select a starting gear or reverse while the truck is stationary.

The clutch brake should not be used during normal moving shifts.

Oil Leaks

Common leak points include the input and output seals, PTO covers, shift housing, auxiliary case, range components, splitter components, and case joints.

Low lubricant can rapidly damage bearings and gears.

Bearing Noise

Whining, rumbling, or growling may indicate worn bearings, damaged gears, low lubricant, driveline vibration, or incorrect driveshaft angles.

Transmission Overheating

Overheating may result from low lubricant, incorrect oil, excessive operating weight, severe grades, improper vehicle gearing, driveline problems, or inadequate cooling.

Shift-Lever Vibration

Some lever movement is normal. Excessive vibration can result from worn isolators, damaged mounts, driveshaft imbalance, incorrect driveline angles, or internal wear.

Auxiliary-Section Wear

Repeated shifting under torque, air-system problems, poor maintenance, or incorrect operation can damage the splitter and range components.

Buying Considerations

Identify the complete Eaton model number.
Confirm the transmission’s maximum torque rating.
Compare the rating with the engine’s programmed torque.
Verify the exact ratio set.
Confirm the overdrive top-gear ratio.
Check compatibility with the rear-axle ratio.
Calculate expected cruising rpm with the intended tire size.
Inspect the transmission identification tag.
Confirm whether the model remains in production.
Check parts and remanufactured-unit availability.
Inspect the case, seals, PTO covers, and auxiliary section for leaks.
Examine the lubricant for metal contamination.
Shift through all eighteen forward ratios during a road test.
Test all four reverse ratios where safe and practical.
Verify every splitter shift.
Test the low-to-high range change.
Check for delayed auxiliary shifts.
Listen for bearing and gear noise.
Check whether the transmission jumps out of gear.
Inspect the clutch and clutch brake.
Review the condition of the shift knob and air controls.
Inspect engine and transmission mounts.
Check driveshafts, universal joints, and carrier bearings.
Confirm PTO compatibility when required.
Review maintenance and rebuild records.
Determine whether external transmission cooling is needed.
Compare repair, rebuilding, and replacement costs.

Variants and Configurations

Eaton Fuller RT-18
Eaton Fuller Roadranger 18-Speed
RTLO-14918B
RTLO-16918B
RTLO-18918B
RTLO-20918B
RTLO-22918B
1,450 lb-ft Configuration
1,650 lb-ft Configuration
1,850 lb-ft Configuration
2,050 lb-ft Configuration
2,250 lb-ft Configuration
Overdrive Configuration
Linehaul Configuration
Heavy-Haul Configuration
Extreme-Duty Configuration
Logging Configuration
Mining Configuration
Oilfield Configuration
PTO-Equipped Configuration
Integral Oil-Pump Configuration
Externally Cooled Configuration
Factory-Remanufactured Configuration

Comparison to Similar Equipment

Compared with the Eaton Fuller 10-speed, the 18-speed offers considerably more ratio flexibility, deeper starting reduction, and closer spacing between gears. The 10-speed is easier to learn and sufficient for most general highway freight, while the 18-speed is better suited to demanding heavy-haul and severe-duty applications.

Compared with the Eaton Fuller 13-speed, the 18-speed allows the driver to split gears in both low and high ranges. The 13-speed normally splits only its upper-range gear positions. The 18-speed therefore provides greater control while starting heavy loads, climbing steep grades, and operating at low speeds.

Compared with a 15-speed manual, the 18-speed provides a more evenly progressive ratio sequence and broader highway flexibility. Traditional 15-speed transmissions often emphasize deep-reduction vocational operation.

Compared with an Eaton UltraShift PLUS or Endurant automated manual, the 18-speed requires the driver to control the clutch and select each ratio. Automated transmissions reduce driver workload, while the 18-speed provides maximum direct control to a skilled operator.

Compared with an Allison fully automatic transmission, the 18-speed uses a driver-operated clutch and direct mechanical gear selection. An Allison may provide smoother low-speed maneuvering, while the 18-speed offers greater manual control and broad ratio selection for heavy highway combinations.

Best Fit For

Extreme heavy-haul carriers
Oversized-load transportation companies
Multi-axle heavy-haul tractors
Logging operations
Mining companies
Oilfield transportation
Construction equipment haulers
Lowboy and RGN carriers
Agricultural equipment transporters
Mountain-route operations
Crane and rigging companies
Specialized machinery movers
Drivers operating high-torque engines
Owner-operators wanting maximum gear control
Vocational trucks requiring PTO equipment
Applications requiring deep starting reduction
Experienced commercial drivers

Related Truck Types

Heavy-Haul Trucks
Vocational Trucks
Sleeper Trucks
Day Cab Trucks
Class 8 Highway Tractors
Logging Trucks
Mining Trucks
Oilfield Trucks
Construction Trucks
Severe-Duty Trucks

Related Truck Models

Related Engines

Related Transmission Types

Manual Transmissions
Heavy-Duty Transmissions
18-Speed Transmissions
Range-Splitter Transmissions
Overdrive Transmissions
Heavy-Haul Transmissions
Severe-Duty Transmissions
Non-Synchronized Transmissions

Related Equipment Systems

Clutch Systems
Clutch Brakes
Driveshafts
Axles and Differentials
Transmission Lubrication Systems
Transmission Cooling Systems
Range-Shift Air Systems
Splitter Systems
Gearshift Controls
PTO Systems

Related Guides

Understand the operating principles in How Commercial Truck Transmissions Work, compare drivetrain designs in Manual vs Automated Manual vs Automatic Transmissions, and evaluate gearing, application, and compatibility in How to Choose a Commercial Truck Transmission.

Regulatory and Compliance Notes

The Eaton Fuller 18-speed must be installed and operated within the engine-torque and application limits approved for the specific transmission model.

Although Eaton lists the RT-18 family with unlimited maximum GCW, the complete vehicle does not have unlimited legal or mechanical capacity.

The truck remains limited by its gross vehicle weight rating, gross combination weight rating, axle ratings, tire ratings, frame, suspension, brakes, driveline components, federal bridge-formula requirements, state laws, and permit conditions.

Many applications using an Eaton Fuller 18-speed involve oversized or overweight freight. These movements may require permits, approved routes, warning signs, flags, lights, travel-time restrictions, escort vehicles, and bridge analysis.

Engine programming should not exceed the transmission’s approved input-torque rating. Performance modifications can overload the clutch, transmission, driveshaft, differentials, and axles.

Replacement transmissions should match the original drivetrain application or be approved as part of a properly engineered conversion.

PTO installations must use properly rated equipment with appropriate controls, guards, lubrication, and operating procedures.

Real World Operating Notes

In real-world operation, drivers rarely need all eighteen ratios during every acceleration. The available gears allow the operator to select the progression that fits the load, terrain, and traffic conditions.

A lightly loaded truck may skip several ratios. An extremely heavy combination beginning on a grade may require nearly every available gear.

The splitter is especially valuable when climbing. The driver can make a smaller ratio change and maintain engine rpm without losing as much momentum as would occur with a conventional 10-speed.

The deep starting ratios reduce the amount of clutch slipping needed to move a heavy combination. The driver should still select the highest starting ratio that moves the load smoothly without excessive clutch stress.

Range and splitter shifts should always be preselected. Split shifts complete when the driver briefly removes torque, while range shifts complete as the shift lever passes through neutral.

The driver should never force the lever into gear or repeatedly move the splitter while waiting for a shift.

On steep grades, the next ratio should be selected before engine speed falls too far. Missing a shift with a heavily loaded combination can result in a rapid loss of momentum.

Frequently Asked Questions

How many gears does an Eaton Fuller 18-speed have?

It has eighteen forward ratios and four reverse ratios.

How does the transmission create eighteen forward speeds?

It combines a five-speed main section with low and high ranges and a direct-overdrive splitter. The low- and high-range gear positions can be split.

Does the driver have to use all eighteen gears?

No. Drivers can skip ratios when the truck’s weight, terrain, and traffic conditions allow.

What is the difference between the range selector and splitter?

The range selector changes between low and high ranges. The splitter divides each gear position into direct and overdrive ratios.

Is the Eaton Fuller 18-speed synchronized?

No. The main transmission is non-synchronized. The driver must match engine speed with road and transmission speed during lever shifts.

What is the maximum torque capacity?

Depending on the model, Eaton Fuller 18-speed transmissions are available with ratings reaching approximately 2,250 lb-ft.

Why is an 18-speed popular for heavy haul?

Its deep starting ratios, close gear spacing, high torque capacity, and ability to split both low- and high-range gears provide excellent control with heavy loads.

What is the difference between a 13-speed and an 18-speed?

A 13-speed normally splits only the high-range gears. An 18-speed allows both the low- and high-range gear positions to be split.

Can an 18-speed be used for ordinary highway freight?

Yes. The driver can skip unnecessary ratios. However, a 10-speed, 12-speed automated transmission, or 13-speed may be sufficient for many general-freight operations.

Can a PTO be installed on an Eaton Fuller 18-speed?

Many models provide PTO openings. The PTO must match the transmission model, mounting opening, rotation, speed, torque requirement, lubrication, and duty cycle.

Why will the splitter not shift?

Possible causes include failure to release driveline torque, low air pressure, an air leak, defective controls, damaged lines, worn cylinder components, contamination, or internal auxiliary-section wear.

Is the Eaton Fuller 18-speed still available?

Availability depends on the exact model. Eaton has discontinued certain RTLO configurations, but parts, service information, remanufactured units, and used transmissions remain widely available.

Availability and Where to Find

Eaton Fuller 18-speed manual transmissions are available through commercial truck dealers, Eaton-authorized service locations, drivetrain specialists, heavy-truck transmission rebuilders, salvage operations, parts suppliers, auctions, and used commercial equipment marketplaces.

Buyers may find new-old-stock, factory-remanufactured, independently rebuilt, and used take-out units.

Because certain RTLO models have been discontinued, buyers should confirm current parts support, model supersessions, warranty coverage, core charges, torque ratings, ratio sets, PTO provisions, and installation compatibility.

Many Eaton Fuller transmissions look similar externally. The identification tag and original truck specifications should be used to verify the model.

Current information and technical resources are available through the official Eaton RT-18 page.

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