🛠️ Squarebody Chevy Axle Guide (1973–1987 C/K-Series)


The drivetrain in your Squarebody starts at the axles—whether you're crawling rocks or cruising pavement. Understanding what axles came stock in your truck helps you plan your build, decode gear ratios, and avoid costly mistakes.

This guide covers every factory front and rear axle found in 2WD and 4WD Squarebody Chevy/GMC trucks from 1973 to 1987. You'll find axle IDs, pros and cons, strengths, weaknesses, and how to identify what you're working with—whether it's a lightweight 10-bolt or a heavy-duty Dana 60.


⚙️ Axle Reference Chart – C & K Series (1973–1987)

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Factory Axles in Squarebody Chevy/GMC Trucks (1973–1987)

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FRONT AXLES (4x4 Trucks Only)

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  Axle Name         Type            Application                       Notes             

|--------------|------------|---------------------|-------------------------------|

  Dana 44          Solid Axle   1/2 & 3/4-ton (K10, K20)   Used until ~1979–1980     

  GM 10-Bolt    Solid Axle   1/2 & 3/4-ton (K10, K20)   Replaced Dana 44       

  Dana 60         Solid Axle   1-ton (K30)                          Kingpin design, HD use     


REAR AXLES (2WD & 4WD)

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  Axle Name            Type             Application                              Notes             

|----------------|------------|---------------------------|-------------------------------|

  GM 12-Bolt        Solid Axle   1/2-ton (C10/K10)                   Used until ~1981       

  GM 10-Bolt        Solid Axle   1/2-ton (C10/K10)                   Replaced 12-bolt       

  Dana 60             Solid Axle   3/4-ton (C20/K20)                  Stronger tubes than 14-bolt   

  GM 14-Bolt SF   Solid Axle   3/4-ton (light duty)                 Semi-float version       

  GM 14-Bolt FF   Solid Axle   3/4-ton & 1-ton (C20/K30)    Full-float, very strong     


📊 Axle Overview – Strengths, Weaknesses & Common Issues


🔧 Dana 44 (Front)

  • Used On: K10, K20 until ~1979
  • Pros: Easy to find, decent strength, kingpin or ball joint versions
  • Cons: Not ideal for big tires or hard wheeling
  • Common Problems: U-joint wear, housing flex under heavy use


🔧 GM 10-Bolt (Front & Rear)

  • Used On: K10/K20 (front), C10/K10 (rear), 1977–1987
  • Pros: Lighter than Dana 44, more available, cheaper parts
  • Cons: Slightly weaker than Dana 44, smaller pinion
  • Common Problems: Pinion bearing failure, broken shafts under load


🔧 Dana 60 (Front & Rear)

  • Used On: K30 (front), C/K20/30 (rear)
  • Pros: Extremely strong, handles big tires and power, kingpin steering
  • Cons: Expensive, heavy, harder to find OEM
  • Common Problems: None major—extremely durable


🔧 GM 12-Bolt (Rear)

  • Used On: 1/2-ton C/K-Series until ~1981
  • Pros: Good strength for light-duty, decent aftermarket
  • Cons: Replaced by 10-bolt, fewer factory gear ratios
  • Common Problems: Carrier bearing wear, housing flex under hard launches


🔧 GM 14-Bolt SF (Semi-Float Rear)

  • Used On: Light-duty 3/4-ton trucks
  • Pros: Stronger than 10/12-bolt, easier maintenance than FF
  • Cons: Not as strong as full-float, no hub service without removing shafts
  • Common Problems: Rear seal leaks, pinion wobble


🔧 GM 14-Bolt FF (Full-Float Rear)

  • Used On: K30/C30 and some K20/C20
  • Pros: Incredibly strong, 10.5" ring gear, ideal for towing/off-road
  • Cons: Heavy, overkill for light-duty builds
  • Common Problems: Worn pinion bearings if neglected, otherwise bulletproof


🔍 Axle Identification Guide

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How to Identify Factory Squarebody Axles

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1. Rear Differential Cover Shape:

  - 10-Bolt: 10 bolt heads, round cover with small tab

  - 12-Bolt: 12 bolts, oval cover

  - 14-Bolt FF: 14 bolts, flat bottom with ribbed center

  - Dana 60: Offset differential, symmetrical round cover


2. Front Axle Hub & Steering Design:

  - Dana 44: Bolt-in spindle, kingpin or ball joint depending on year

  - GM 10-Bolt: Round tubes, ball joints, no kingpins

  - Dana 60 (Front): Kingpin design, thick tubes, flat top knuckles


3. Axle Tube Stampings:

  - Found on passenger side axle tube (front or rear)

  - Use numbers to decode gear ratio and build date


4. Lug Pattern (General Guide):

  - 6 Lug: Typically 1/2-ton

  - 8 Lug: 3/4-ton and 1-ton (Dana 60, 14-bolt FF)


🧰 Common Factory Gear Ratios

Axle Type                    Typical Ratios

GM 10/12 Bolt             3.08, 3.42, 3.73

Dana 44                        3.73, 4.10, 4.56

Dana 60                       4.10, 4.56, 4.88

14-Bolt FF                    3.73, 4.10, 4.56


🔚 Closing Statement

Your axles are the final link between your truck’s power and the trail—or pavement. Whether you're running stock 10-bolts or planning a Dana 60 swap, understanding your factory axle setup is key to building a truck that performs and survives.

This guide walks through every front and rear axle option from 1973–1987, helping you identify what’s under your rig, what it’s good for, and how to move forward with confidence.

For more Squarebody tech, real-world upgrades, and trusted advice, follow Blazin’ Biddles’ Off-Road—where every part has a purpose and every build tells a story.