4L80E vs Allison 1000: Swap Cost, Strength, Should You Switch?

Should you swap your 4L80E for an Allison 1000? It is a popular question on Duramax-swapped trucks and big-HP gas builds. Here is the head-to-head.

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Quick comparison

4L80E:

  • 4-speed with overdrive
  • ~440 ft-lb stock (800+ HD)
  • Used in GM HD trucks, motorhomes
  • HD = 75 lbs

    • Allison 1000:

  • 5-speed (early) / 6-speed (2006+)
  • 520-765 ft-lb stock (1,200+ HD)
  • Used in Duramax 2500HD/3500HD
  • HD = 250 lbs (3x weight of 4L80E)

    • Gear ratios

    4L80E:

  • 1st: 2.48
  • 2nd: 1.48
  • 3rd: 1.00
  • 4th: 0.75 OD

    • Allison 1000 (6-speed):

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

    • Strength comparison

    4L80E:

  • Stock: 440 ft-lb
  • HD parts: 800 ft-lb
  • Race billet: 1500+ ft-lb
  • Affordable HD aftermarket

    • Allison 1000:

  • Stock LB7/LBZ: 520 ft-lb
  • Stock LMM/LML: 765 ft-lb
  • Stock LP5/L5P: 910 ft-lb
  • HD parts: 1,200+ ft-lb
  • Race: 1,500+ ft-lb (Stage 5+)
  • Massive aftermarket Allison community

    • Service / fluid

    4L80E:

  • Dexron VI: $7-$10/qt
  • 12 qt full capacity
  • $80-$120 full service fluid cost
  • Service interval: 50,000 miles

    • Allison 1000:

  • TES-295: $20-$30/qt
  • 18 qt full capacity
  • $360-$540 full service fluid cost
  • Service interval: 50,000 miles (1000), 30,000 miles tow

    • Rebuild cost

    4L80E rebuild:

  • Parts: $500-$900
  • Labor: $1,500-$2,500
  • Total: $2,000-$3,400 (stock)
  • HD: $3,500-$5,000

    • Allison 1000 rebuild:

  • Parts: $1,500-$3,000
  • Labor: $2,500-$4,000
  • Total: $4,000-$7,000 (stock)
  • HD: $7,000-$11,000

    • Driveability comparison

    4L80E shifts:

  • Smooth on freshly built unit
  • Bigger ratio jumps (RPM drops more)
  • Predictable, classic feel

    • Allison shifts:

  • Slower shifts (apply slower for clutch protection)
  • Smaller ratio jumps
  • Heavier feel (more rotational mass)
  • Excellent tow mode logic

    • Allison swap into Ford / non-Duramax truck

    What you need:

  • Allison 1000 trans
  • Allison adapter to your bell housing
  • Standalone TCM controller
  • Wiring harness fabrication
  • Custom driveshaft (Allison spline different)
  • Cooler upgrade

    • Cost:

  • Used Allison: $1,500-$3,000
  • Bell housing adapter: $1,500-$2,500
  • TCM standalone (PCS or ATS): $1,200-$2,000
  • Wiring labor: $1,000-$2,000
  • Driveshaft mod: $300-$700
  • Labor: $2,500-$4,500
  • Total: $8,000-$14,700

    • 4L80E swap into Duramax (replacing Allison)

    Rare but possible:

  • People do this for race trucks (lighter)
  • Allison bell housing not compatible
  • Requires bell adapter + custom mount

    • Cost:

  • Used 4L80E: $600-$1,200
  • Bell adapter: $1,200-$2,000
  • HD build: $3,000-$5,000
  • Driveshaft: $300-$700
  • Labor: $2,000-$3,500
  • Total: $7,100-$12,400

    • When to choose 4L80E

    4L80E is the answer if:

  • Drag racing (lighter = quicker)
  • Cost-sensitive HD build
  • SBC/BBC powered
  • Restomod or carb engine
  • Already a 4L80E swap
  • Limited budget for fluid service

    • When to choose Allison 1000

    Allison is the answer if:

  • Already Duramax-powered truck (factory pair)
  • HD tow (5th wheel, big trailer)
  • Building extreme HP (1000+ HP)
  • Wanting absolute reliability
  • Daily driving with HD use
  • Have budget for proper fluid service

    • Cost-per-mile comparison (over 100k miles)

    4L80E HD build:

  • Initial: $4,500
  • Fluid (2x): $200
  • Total: $4,700 over 100k
  • $0.047/mile

    • Allison HD build:

  • Initial: $9,000
  • Fluid (3x in tow): $1,350
  • Total: $10,350 over 100k
  • $0.103/mile

    • Allison costs ~2x per mile but lasts longer typically

    Resale value impact

    4L80E in Duramax truck:

  • Hurts resale
  • Buyers want stock Allison
  • Discount: $3,000-$8,000

    • Allison in non-Duramax truck:

  • Adds value for HD buyers
  • Premium: $1,500-$4,000
  • But limited buyer pool

    • Recommendation

    Stock or mild tune in Duramax:

  • Keep Allison (always)

    • Big HP Duramax race truck:

  • 4L80E swap can save weight + cost
  • But sacrifices reliability

    • Big HP gas truck:

  • Allison swap if 1000+ HP and budget allows
  • 4L80E HD if budget tight

    • Tow rig:

  • Allison wins for HD use
  • 4L80E adequate for under 12k lbs

    • Need 4L80E or Allison 1000 rebuild parts? Shop our 4L80E catalog or Allison 1000 catalog. HD builds, master kits, converters. Free shipping over $70.

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