Allison 2000 Series Automatic Transmission

Quick Facts

  • Manufacturer: Allison Transmission
  • Transmission Type: Fully Automatic, Torque-Converter Transmission
  • Transmission Family: Allison 1000/2000 Product Family
  • Common Models: 2100, 2200, 2300, 2350, 2500, and 2550
  • Forward Speeds: 5 or 6 depending on model and calibration
  • Reverse Speeds: 1
  • Maximum Input Power: Up to approximately 365 horsepower on current 1000/2000 Series configurations
  • Maximum Input Torque: Up to approximately 700 lb-ft
  • Maximum Published GVW: Up to approximately 33,000 lbs for current standard 1000/2000 Series applications
  • Control Type: Electronic Transmission Control Module
  • Launch System: Hydraulic Torque Converter
  • Lockup System: Electronically Controlled Torque-Converter Lockup Clutch
  • Available Gearing: Close-Ratio and Wide-Ratio Configurations
  • PTO Compatibility: SAE Six-Bolt PTO Provision on Compatible Models
  • Common Truck Classes: Classes 5, 6, and 7
  • Primary Applications: Delivery Trucks, Utility Trucks, School and Shuttle Buses, Emergency Vehicles, Dump Trucks, Tow Trucks, and Medium-Duty Vocational Trucks

Overview

The Allison 2000 Series is a family of electronically controlled, fully automatic transmissions designed primarily for light- and medium-duty commercial vehicles.

It occupies the middle ground between the lighter Allison 1000 Series and the larger Allison 3000 Series. The 2000 family offers greater vocational flexibility and PTO availability than many 1000 Series installations while remaining smaller and lighter than the 3000 Series.

The transmission uses a hydraulic torque converter rather than a dry mechanical clutch. This allows smooth starts, torque multiplication, controlled low-speed movement, and uninterrupted power delivery during many operating conditions.

Depending on the model and calibration, the Allison 2000 Series provides five or six forward ranges. Close-ratio gearing is available for efficiency, while wide-ratio gearing improves startability and low-speed performance.

Common versions include the 2100, 2200, 2300, 2350, 2500, and 2550. Allison also offers application-specific designations for highway, rugged-duty, emergency-vehicle, school-bus, shuttle-bus, motorhome, and specialty applications.

Key Characteristics

The defining characteristic of the Allison 2000 Series is its torque-converter launch system. The converter multiplies engine torque when the vehicle begins moving and permits controlled low-speed operation without slipping a dry clutch.

Once the vehicle is moving, the lockup clutch can mechanically connect the engine and transmission. Lockup reduces converter slippage, heat generation, and fuel consumption.

Electronic controls monitor engine load, vehicle speed, throttle position, brake input, transmission temperature, selected range, and other operating information. The transmission control module then chooses the appropriate gear and lockup strategy.

The 2000 Series uses planetary gearsets and hydraulically applied clutch packs. This design allows shifts to occur without the driver operating a clutch pedal or manually moving through gear positions.

Compatible models can be equipped with a transmission-mounted PTO. This makes the series especially valuable in utility, dump, towing, fire, municipal, and other body-equipment applications.

How the Transmission Works

Engine power enters the transmission through the torque converter. Fluid movement inside the converter transfers torque from the engine-driven impeller to the turbine connected to the transmission’s input shaft.

During launch, the torque converter can multiply engine torque. This helps a loaded truck begin moving without requiring the driver to slip a mechanical clutch.

The transmission control module directs hydraulic pressure to specific internal clutch packs. Each clutch combination holds or drives portions of the planetary gearsets to create the selected gear ratio.

As vehicle speed increases, the control system shifts through the forward ranges. The driver normally selects Drive and allows the transmission to manage all gear changes automatically.

The torque-converter lockup clutch engages when operating conditions permit. Lockup creates a more direct mechanical connection, reducing heat and improving efficiency.

During deceleration or heavy load operation, the transmission can downshift to maintain performance. Available programming can coordinate shifting with engine controls and vehicle systems.

When a PTO is installed, the transmission and vehicle controls must determine when the PTO is allowed to engage, what engine speed is required, and whether the vehicle can remain stationary or move during operation.

Common Specifications

Transmission Type

The Allison 2000 Series is a fully automatic transmission using a hydraulic torque converter, planetary gearsets, electronic controls, and hydraulically applied clutch packs.

Forward Speeds

Depending on the model and vehicle programming, the transmission provides five or six forward ranges.

Some earlier or specially calibrated installations may have the sixth range electronically disabled even when the internal hardware is capable of six-speed operation.

Close-Ratio Gear Configuration

A common close-ratio six-speed arrangement includes:

  • 1st: 3.10:1
  • 2nd: 1.81:1
  • 3rd: 1.41:1
  • 4th: 1.00:1
  • 5th: 0.71:1
  • 6th: 0.61:1
  • Reverse: 4.49:1

The close-ratio configuration emphasizes efficient progression between gears and highway operation.

Wide-Ratio Gear Configuration

A common wide-ratio arrangement used in applicable 2500 and 2550 configurations includes:

  • 1st: 3.51:1
  • 2nd: 1.90:1
  • 3rd: 1.44:1
  • 4th: 1.00:1
  • 5th: 0.74:1
  • 6th: 0.64:1
  • Reverse: 5.09:1

The deeper first and reverse ratios improve startability and low-speed performance.

Direct Drive

Fourth gear is commonly the 1.00:1 direct-drive ratio.

Overdrive

Fifth and sixth ranges provide overdrive gearing. Sixth gear offers the lowest cruising ratio when enabled.

Input Power

Current Allison information groups the 1000 and 2000 Series across power ratings from approximately 210 to 365 horsepower.

The approved rating depends on the exact transmission model, torque converter, vehicle weight, engine calibration, and application.

Input Torque

Current published torque capacity reaches approximately 700 lb-ft for compatible 1000/2000 Series configurations.

Some individual models, earlier generations, and calibrations carry lower ratings.

Vehicle Weight Rating

Current standard 1000/2000 Series product information lists applications with gross vehicle weights reaching approximately 33,000 pounds.

The transmission rating does not independently establish the truck’s GVWR. The chassis, axles, brakes, tires, suspension, frame, and certification label determine the vehicle’s approved weight.

Torque Converter

The converter provides hydraulic torque multiplication during launch. Different converter models are available to match engine torque, vehicle weight, tire size, axle ratio, and application.

Lockup Clutch

An electronically controlled lockup clutch reduces converter slippage after launch.

Lockup strategy varies according to transmission calibration, throttle position, load, speed, temperature, and operating mode.

Internal Gear Design

The transmission uses planetary gearsets with hydraulically applied clutch packs.

Its helical gears and automatic controls support smooth commercial operation and reduced driver workload.

Electronic Controls

The transmission control module receives information from:

  • Engine controls
  • Input-speed sensor
  • Turbine-speed sensor
  • Output-speed sensor
  • Accelerator controls
  • Brake system
  • Range selector
  • Temperature sensors
  • Vehicle body controls
  • PTO controls

The TCM uses this information to manage shifting, converter lockup, protection functions, diagnostics, and prognostics.

FuelSense 2.0

FuelSense 2.0 uses electronic shift and lockup strategies intended to reduce fuel consumption without sacrificing required vehicle performance.

Feature availability depends on the transmission, vehicle manufacturer, application, and calibration.

Park Position

A park pawl is available on certain models, particularly configurations intended for vehicles using a conventional Park position.

Other models rely on the vehicle’s parking brake and use a range selector without a mechanical transmission Park position.

PTO Provision

Compatible Allison 2000 Series models may include an SAE six-bolt PTO opening.

PTO availability depends on the model, case, internal drive gear, application code, and original vehicle specification.

Lubrication

Allison-approved TES 668 or TES 295 automatic transmission fluid is commonly recommended for commercial on-highway applications.

Fluid type, capacity, and service interval must be confirmed for the exact transmission model and sump configuration.

Filters

The transmission uses internal filtration and an externally serviceable control-main spin-on filter on applicable models.

Allison prognostic systems can monitor fluid, filter, and transmission condition when enabled by the vehicle manufacturer.

Cooling System

The transmission requires an approved oil cooler and properly routed cooler lines.

Cooling capacity must account for vehicle weight, torque-converter operation, road speed, ambient temperature, PTO use, and vocational duty cycle.

Transmission Weight

Dry weight varies by model, torque converter, PTO provisions, sump, parking-brake equipment, and output arrangement.

Buyers should use the model identification tag and vehicle build information rather than applying one weight figure to the entire 2000 Series.

Installation Requirements

Installation requires a compatible engine, flywheel housing, flexplate, torque converter, transmission controller, wiring, shift selector, cooler, driveshaft, rear axle, mounts, and vehicle programming.

Common Applications

  • Pickup and delivery trucks
  • Box trucks
  • Refrigerated delivery trucks
  • Utility-service trucks
  • Bucket trucks
  • Dump trucks
  • Tow trucks
  • Rollback carriers
  • Emergency vehicles
  • Fire apparatus
  • Ambulances
  • School buses
  • Shuttle buses
  • Municipal vehicles
  • Landscape trucks
  • Contractor trucks
  • Beverage-delivery trucks
  • Motorhomes
  • Small refuse vehicles
  • Airport-service vehicles
  • PTO-equipped vocational trucks

Truck and Engine Compatibility

The Allison 2000 Series is used across numerous medium-duty truck platforms. Exact availability depends on model year, engine, chassis rating, vocation, and manufacturer option packages.

Common truck platforms include:

Certain trucks may use another Allison family depending on engine torque and GVWR. For example, heavier Kenworth T280, Peterbilt 536, Freightliner M2, or International vocational configurations may require an Allison 3000 Series transmission.

Common engine families include:

Engine compatibility must be based on the exact horsepower and torque rating. Some higher-output versions of the Cummins L9, PACCAR PX-9, or Detroit DD8 may exceed the rating of a particular 2000 Series transmission and require an Allison 3000 Series.

Advantages

  • Smooth torque-converter launches
  • No manual clutch pedal
  • Excellent stop-and-go drivability
  • Good low-speed control
  • Reduces driver training requirements
  • Suitable for numerous medium-duty applications
  • Five- and six-speed configurations are available
  • Close- and wide-ratio gearing is available
  • Compatible models support PTO equipment
  • Electronic controls provide consistent shifting
  • Torque-converter lockup improves efficiency
  • FuelSense programming can reduce fuel consumption
  • Prognostics can simplify maintenance planning
  • Broad service and parts support
  • Well-established commercial transmission family
  • Good compatibility with vocational body equipment
  • Generally lighter and less expensive than an Allison 3000 Series

Limitations or Considerations

  • Lower torque capacity than the Allison 3000 Series
  • Torque-converter operation can generate substantial heat
  • Incorrect cooling capacity can shorten transmission life
  • Not every model includes a PTO opening
  • Not every version has a mechanical Park position
  • Fluid specification affects service intervals
  • Electronic diagnosis requires compatible equipment
  • Different models have different ratings and gear ratios
  • The Allison name alone does not establish compatibility
  • Used units may require controller programming
  • Converter selection strongly affects performance
  • Excessive vehicle weight can damage the transmission
  • Higher-output medium-duty engines may require a larger transmission
  • A fully automatic transmission can weigh more than an automated manual

Driver and Operator Experience

The Allison 2000 Series provides familiar automatic-transmission operation. The driver selects Drive, Reverse, Neutral, or Park where equipped and operates the accelerator and brake pedals.

The torque converter allows the truck to begin moving smoothly without direct clutch engagement. This is particularly valuable in congested traffic, delivery work, backing, towing, and vocational job-site operations.

Drivers can often select a lower range when descending grades or operating in difficult terrain. The transmission’s controls may still prevent a downshift that would overspeed the engine.

Vehicles with push-button or electronic selectors display the selected range and the highest available gear. Drivers should understand the difference between the selected range and the actual gear currently engaged.

Operators should not shift from Drive to Reverse while the truck is moving. The vehicle should be stopped completely and the service brake applied before changing direction.

Transmission-temperature warnings should never be ignored. Continued torque-converter operation while overheated can damage fluid, seals, clutch packs, and the converter.

Maintenance and Ownership Notes

Use only fluid approved for the exact Allison model and vehicle application. Allison-approved TES 668 or TES 295 fluids generally support improved durability and longer service intervals.

Fluid level should be checked according to Allison’s procedure. Some vehicles support electronic fluid-level checking through the transmission selector.

The transmission cooler, hoses, fittings, seals, wiring, electrical connectors, range selector, breather, and external filter should be inspected regularly.

General-duty and severe-duty service intervals differ. Stop-and-go delivery, refuse, towing, emergency response, construction, and PTO use may require shorter intervals.

Allison prognostics can monitor fluid life, filter life, and transmission health when the feature is enabled in the TCM and supported by the vehicle.

The correct spin-on control-main filter should be installed. Low-quality or incorrect filters can restrict flow or provide inadequate protection.

After major repairs or replacement, the TCM may require programming, calibration, or adaptive shifting procedures.

Common Transmission Problems

Fluid Leaks

Leaks commonly occur around cooler lines, seals, the pan, filter, PTO opening, output area, and electrical connector.

Overheating

Low fluid, restricted cooling, prolonged converter operation, overloading, towing, or an unsuitable converter can cause high transmission temperature.

Harsh Shifting

Possible causes include degraded fluid, incorrect fluid level, valve-body problems, solenoid faults, sensor failures, wiring problems, or improper calibration.

Delayed Engagement

A delay when selecting Drive or Reverse may indicate low fluid, internal leakage, worn clutch packs, converter drain-back, filter restriction, or hydraulic problems.

Failure to Shift

Electrical faults, failed speed sensors, damaged wiring, solenoid problems, low hydraulic pressure, or internal clutch damage can prevent normal shifting.

Limp Mode

When the TCM detects a serious fault, it may restrict the transmission to one gear or a limited operating range to protect the unit.

Torque-Converter Shudder

Shudder during lockup can result from degraded fluid, clutch wear, incorrect calibration, converter problems, or engine-performance issues.

PTO Problems

A PTO may fail to engage because of incorrect programming, failed interlocks, wiring faults, improper PTO selection, or insufficient hydraulic pressure.

Worn Clutch Packs

Overheating, contaminated fluid, excessive weight, or prolonged operation with unresolved problems can damage the internal friction clutches.

Speed-Sensor Faults

Failed input, turbine, or output-speed sensors can cause incorrect shifting, fault codes, or limp mode.

Buying Considerations

  • Identify the complete Allison model number.
  • Record the transmission serial number.
  • Confirm whether it is a 2100, 2200, 2300, 2350, 2500, or 2550.
  • Determine whether it has five or six enabled forward ranges.
  • Verify close-ratio or wide-ratio gearing.
  • Confirm the maximum approved engine torque.
  • Check the vehicle’s GVWR and intended payload.
  • Verify engine compatibility.
  • Identify the installed torque-converter model.
  • Confirm whether a PTO opening and internal drive gear are present.
  • Determine whether a Park position is required.
  • Check the sump depth and fluid capacity.
  • Confirm the approved fluid specification.
  • Scan the TCM for active and stored diagnostic codes.
  • Review fluid-temperature and overheat history.
  • Inspect the fluid for discoloration, odor, or contamination.
  • Check cooler lines, seals, filter, wiring, and connectors.
  • Test Drive and Reverse engagement.
  • Road-test all available forward ranges.
  • Verify converter lockup operation.
  • Review maintenance and rebuilding records.
  • Confirm that replacement programming is available.

Variants and Configurations

  • Allison 2100
  • Allison 2100 HS
  • Allison 2100 RDS
  • Allison 2100 EVS
  • Allison 2100 PTS
  • Allison 2200
  • Allison 2200 HS
  • Allison 2200 RDS
  • Allison 2200 EVS
  • Allison 2200 PTS
  • Allison 2300
  • Allison 2300 HS
  • Allison 2300 RDS
  • Allison 2350
  • Allison 2500
  • Allison 2500 HS
  • Allison 2500 RDS
  • Allison 2500 EVS
  • Allison 2500 PTS
  • Allison 2550
  • Five-Speed Configuration
  • Six-Speed Configuration
  • Close-Ratio Configuration
  • Wide-Ratio Configuration
  • PTO-Equipped Configuration
  • Park-Pawl Configuration

Comparison to Similar Equipment

Compared with the Allison 1000 Series, the 2000 Series generally supports heavier commercial chassis and broader vocational applications. Compatible 2000 models also offer stronger PTO flexibility.

Compared with the Allison 3000 Series, the 2000 Series is smaller and suited to lower engine torque and vehicle weights. The 3000 Series supports engines reaching approximately 1,250 lb-ft and substantially heavier vehicles.

Compared with the Allison 2500 Series, the name 2500 identifies a specific group within the broader 2000 Product Family. A separate 2500 page can focus on its wide-ratio gearing and particular vocational applications.

Compared with the PACCAR TX-8, both serve medium-duty commercial trucks. The TX-8 provides eight forward gears, while the standard Allison 2000 generally provides five or six. The Allison has a long-established vocational and PTO support network.

Compared with an Eaton automated manual transmission, the Allison uses a torque converter rather than a dry launch clutch. This gives the Allison smoother low-speed behavior but can increase heat, weight, and converter losses.

Best Fit For

  • Medium-duty delivery fleets
  • Box truck operators
  • Utility companies
  • Municipal fleets
  • School and shuttle buses
  • Emergency-service vehicles
  • Fire apparatus
  • Tow trucks
  • Rollback carriers
  • Dump truck fleets
  • Landscape contractors
  • Construction-support operations
  • PTO-equipped service trucks
  • Stop-and-go urban routes
  • Fleets prioritizing easy driver operation
  • Applications requiring torque-converter launch performance

Related Truck Types

Related Truck Models

Related Engines

Related Transmission Types

Related Equipment 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 transmission must be installed and operated within Allison’s approved engine-power, input-torque, vehicle-weight, cooling, and vocational ratings.

The transmission rating does not establish the completed vehicle’s legal carrying capacity. Operators must follow the truck’s GVWR, GAWR, tire ratings, axle limits, and applicable weight laws.

Electronic controls communicate with the engine, braking system, instrument panel, PTO equipment, and vehicle controllers. Replacement components may require correct programming to preserve safety, diagnostic, and emissions-system communication.

PTO-driven equipment must include properly rated pumps, shafts, guards, controls, and safety interlocks.

Emergency, school-bus, passenger, and vocational vehicles may be subject to additional federal, state, local, or industry-specific requirements.

Real World Operating Notes

The Allison 2000 Series performs especially well in stop-and-go service where a manual or automated manual clutch would experience frequent engagement cycles.

Its torque converter makes docking, backing, trailer positioning, and low-speed vocational work smoother and easier for many drivers.

Transmission heat is the main concern during prolonged converter operation. Drivers should avoid holding the truck with accelerator pressure and should monitor temperature during towing, climbing, or PTO work.

Correct converter selection is important. A converter that does not match the engine, axle ratio, tire size, and vehicle weight can produce weak acceleration, excessive heat, or poor efficiency.

Many used vehicles are advertised simply as having an “Allison automatic.” Buyers should locate the identification tag because an Allison 1000, 2000, 2500, and 3000 can have substantially different ratings and capabilities.

Frequently Asked Questions

What is the Allison 2000 Series?

It is a family of fully automatic, torque-converter transmissions designed primarily for light- and medium-duty commercial vehicles.

How many gears does it have?

Most configurations provide five or six forward ranges and one reverse range.

How much torque can it handle?

Current Allison information lists capacity reaching approximately 700 lb-ft for compatible 1000/2000 Series configurations.

What is the difference between the Allison 1000 and 2000?

The 2000 Series generally supports heavier commercial vehicles and broader vocational configurations, including greater PTO availability on compatible models.

Is the Allison 2500 part of the 2000 Series?

Yes. The Allison 2500 is a model group within the broader 2000 Product Family.

Does it have a torque converter?

Yes. The torque converter provides smooth launch performance and torque multiplication.

Does every Allison 2000 have six speeds?

No. Some models or calibrations use five forward ranges, while others provide six.

Can it operate a PTO?

Compatible models can be equipped with an SAE six-bolt PTO opening and internal drive gear. PTO availability must be confirmed for the exact transmission.

Does every Allison 2000 have Park?

No. Park-pawl availability varies. Some commercial configurations rely on the vehicle parking brake rather than a mechanical transmission Park position.

What fluid does it use?

Many commercial applications use Allison-approved TES 668 or TES 295 fluid. The correct specification must be confirmed for the individual transmission.

Is the Allison 2000 suitable for a Class 8 truck?

It is primarily intended for Classes 5 through 7. Heavier Class 8 applications generally require an Allison 3000 or larger transmission.

Can an Allison 2000 replace an Allison 1000?

Not automatically. Mechanical dimensions, controls, output arrangements, PTO equipment, programming, ratings, and vehicle integration must all be verified.

Availability and Where to Find

New Allison 2000 Series transmissions are available through commercial truck manufacturers, authorized Allison distributors, and participating vehicle dealers.

Replacement transmissions, torque converters, controllers, valve bodies, PTO components, filters, and service parts are available through Allison-authorized service locations, commercial drivetrain suppliers, remanufacturers, salvage operations, and used truck-parts dealers.

A used transmission should be identified by its complete model and serial number. Buyers should not rely only on the Allison name or the general 2000 Series designation.

Before purchasing a replacement, verify the engine rating, torque converter, gear ratios, output arrangement, parking provision, PTO opening, sump, electronic controls, vehicle weight, and application calibration.

Current product information and distributor support can be found through Allison Transmission’s official 1000 and 2000 Series page.

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