Allison 1000 / 2000 Series
Automatic • 6-speed • Allison Transmission
About the Allison 1000 / 2000 Series
The Allison 1000 series (Class 3-5, lighter applications) and 2000 series (Class 5-7, heavier applications) are the dominant medium-duty automatic transmissions. Used in GM Heavy Duty pickups (Duramax + Allison 1000), Chevrolet Silverado 4500HD/5500HD/6500HD medium-duty (Allison 2500/3500), Hino and Isuzu medium-duty trucks, and many municipal/utility vehicles. The Allison 1000 is the standard transmission in every Duramax-equipped Chevy/GMC HD pickup — many drivers buy GM specifically because of the Allison transmission pairing.
Overview
The Allison 1000 series (Class 3-5, lighter applications) and 2000 series (Class 5-7, heavier applications) are the dominant medium-duty automatic transmissions. Used in GM Heavy Duty pickups (Duramax + Allison 1000), Chevrolet Silverado 4500HD/5500HD/6500HD medium-duty (Allison 2500/3500), Hino and Isuzu medium-duty trucks, and many municipal/utility vehicles. The Allison 1000 is the standard transmission in every Duramax-equipped Chevy/GMC HD pickup — many drivers buy GM specifically because of the Allison transmission pairing.
Specifications
- Manufacturer
- Allison Transmission
- Type
- Automatic
- Gear count
- 6
- Torque capacity
- 660 lb-ft
- Truck classes
- Class 3-7
- Applications
- Medium-duty pickup, vocational, delivery, school bus
- Production years
- 2001–present
Design and engineering
6-speed automatic with torque converter. Compact design for medium-duty applications. PTO options for vocational accessories.
Generations and updates
Reliability and longevity
Allison 1000 in Duramax GM trucks is legendary for reliability — often outlasts the truck. Allison 2000 in medium-duty is similarly durable. Heat management in heavy-load applications (heavily-modified Duramax trucks) is the primary failure factor.
Common problems
Allison 1000: shift programming issues on heavily-tuned/modified trucks. Torque converter lockup issues at high mileage. Allison 2000: refuse-application heat stress on shorter routes.
Maintenance schedule
Fluid + filter every 100,000 miles (pickup/light commercial), 75,000 miles (vocational).
Driver experience
Smooth automatic — most familiar transmission for medium-duty drivers transitioning from passenger vehicles.
Pros and cons
✓ Pros
- • Allison reliability
- • Smooth automatic operation
- • PTO options
- • Strong resale impact
- • Standard in GM HD trucks
⚠ Cons
- • Heavier than competing automatics
- • Higher cost
- • Fuel economy penalty vs AMT in highway use (less critical for medium-duty)
Resale value impact
Strong — Duramax + Allison 1000 in Chevy/GMC HD pickups significantly improves resale. Allison-equipped medium-duty trucks (Chevy 4500/5500HD, Hino, Isuzu) command premium over equivalent manual or non-Allison-equipped trucks.