Allison 2400 vs 1000: Differences, Applications, Strength

The Allison 2400 is the medium-duty truck version of the legendary Allison 1000. Same family but different sizing. Here is the comparison.

Production years

Allison 1000:

  • 2001-current
  • 5-speed (early) / 6-speed (2006+)
  • Used in: Chevy/GMC 2500HD/3500HD Duramax

Allison 2400:

  • 2002-current
  • 5-speed / 6-speed
  • Used in: GMC C4500/C5500, Chevy Kodiak, Isuzu NPR/NRR (some), Workhorse W-series

What they share

  • Same internal clutch architecture (C1-C5)
  • Same TES-295 fluid spec
  • Same TCM platform (different calibration)
  • Same pan style (16-bolt)
  • Many internal parts interchange

Key differences

Torque rating:

  • 1000: 520-700 ft-lb input
  • 2400: 850-1,150 ft-lb input
  • 2400 has HD planetaries

Case size:

  • 2400 is physically larger
  • HD bell housing
  • HD output shaft (different yoke)

Cooling:

  • 2400 has larger internal cooler passages
  • Better heat handling
  • Required for medium-duty truck use

Clutch material:

  • 2400 uses HD friction material
  • C2 pack has 7 discs (vs 5-6 in 1000)

Parts interchange

Mostly same:

  • Pan and filter (most years)
  • External harness
  • TCM connector pinout
  • Many solenoids

Different:

  • Bell housing pattern
  • Output shaft (yoke and spline)
  • Some clutch packs (HD on 2400)
  • Planetary sets

    • When you would encounter 2400

    • Box truck / U-Haul rental fleet
    • School bus / shuttle bus
    • Heavy-duty work truck (5-6 ton GVW)
    • Older RV / motorhome

    2400 service

    Fluid:

  • TES-295 required
  • 20+ quarts full capacity
  • $300-$500 for full service

    • Filters:

  • Internal: same as 1000 (mostly)
  • External spin-on: required service item
  • Both PNs different from 1000 in some years

    • Service interval:

  • Stock use: 50,000 miles
  • Heavy-duty: 25,000-35,000 miles
  • Both filters at same interval

    • Common 2400 failures

    C2 clutch:

    External harness:

  • Heat-related failure
  • $200-$400 part
  • Required for valid sensor signal

    • Output shaft seal:

  • Same failure mode as 1000
  • Read our Allison 1000 output shaft seal

    • Cost

    2400 service:

    • Filters + fluid: $400-$650
    • Labor: $300-$500
    • Total: $700-$1,150

    2400 rebuild:

    • Parts: $3,500-$5,500
    • Labor: $2,500-$3,500
    • Total: $6,000-$9,000

    1000 rebuild for comparison:

  • Parts: $2,800-$4,500
  • Labor: $2,000-$3,000
  • Total: $4,800-$7,500

    • When to choose 2400 over 1000

    2400 required if:

  • Medium-duty truck (4500-5500)
  • Box truck use
  • Shuttle bus / RV
  • Sustained heavy load over 12,000 lbs

    • 1000 fine if:

  • 1-ton or smaller pickup
  • Towing 14k lbs or less
  • Tuned Duramax

    • Need Allison 2400, 1000, or HD parts? Shop our Allison 2400 catalog. HD clutches, planetary sets, complete rebuild kits. Free shipping over $70.

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