1973-1987 Three-Quarter and 1-Ton GM Rear Axle Identification Guide

From 1973 to 1987, GM equipped its three-quarter and 1-ton trucks with what would become known as the original Corporate 14-Bolt rear axle. These full-floating axles were designed for heavy-duty use and are widely respected for their strength, durability, and serviceability.

Key Features

• Axle Construction:
  Cast-iron differential center section with smooth casting on top and pressed-in steel axle tubes. Full-floating spindles allow shafts to be removed without lifting the vehicle.
• Axle Shafts:
  30-spline, 1.5" diameter; attached using eight 1/2"-13 x 1.25" grade 9 bolts.
• Wheel Hubs:
  8-lug design, used on both 3/4-ton and 1-ton trucks.
• Differentials:
  Offered with open carrier, G80 Gov-Lock, or Detroit Locker (military versions).
• Gear Ratios Available:
  3.73:1, 4.10:1, 4.56:1
• Brakes:
  Drum brakes standard
  3/4-ton: 11" or 13" diameter
  1-ton: 11" or 13" diameter
• Axle Width:
  67.5" from wheel mounting surface to wheel mounting surface
• Axle Tube Size:
  3.375" diameter with 0.5" wall thickness
• Pinion Support:
  Bolted-in, typically with 1350-series yoke
• Differential Cover:
  14-bolt stamped steel "Superman shield" design
• Fill Plug:
  Located near pinion

Notable Variations

• Chassis Cab (Dually) Axles:
  Hub flange location flipped to reduce WMS-to-WMS for dual-rear-wheel use to 63.5".
• 1984-1985 Model Year:
  Some units feature unique pinion straddle bearing on the head of the pinion gear.
• CUCV Military Version:
  Factory 4.56 gears and Detroit Locker replaced spider gears in open carrier housing.
• Dual Rear Wheel Pickups:
  Did not use Corporate 14-bolt. Most were equipped with Dana 70 rear axles.

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This axle series has become a legend among off-roaders, builders, and restoration enthusiasts for its unbeatable strength-to-cost ratio. If your GM truck has one, you're working with one of the most trusted rear axles in heavy-duty history.

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