🔧 Squarebody Chevy Driveline Guide (1973–1987 C/K-Series)
Your Squarebody's driveline is the critical link between your transmission, transfer case, and axles. Whether you’re running a stock height truck or a lifted rig with a dual case setup, understanding driveshaft geometry, U-joint alignment, and pinion angle is the key to eliminating vibration and building something reliable.
This guide walks through every type of factory driveline used in C/K-Series Squarebody Chevys and gives you the knowledge to build, repair, or upgrade your drivetrain the right way.
⚙️ Factory Driveline Styles
Squarebody trucks used several different driveline styles depending on model, wheelbase, drivetrain, and year. Here’s a breakdown:
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Factory Driveshaft Types – Squarebody Chevy C/K-Series (1973–1987)
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| Model | Front Driveshaft | Rear Driveshaft | Notes
|
K10 (short) | Single-piece CV | Single-piece | Standard for most K10s
| K10 (long) | Single or 2-piece CV | 2-piece with center carrier | Long beds, smoother ride
| K20/K30 | Single-piece CV or fixed | 2-piece with carrier bearing | Larger tubing, stronger yokes
| C10 (2WD) | N/A (no front shaft) | Single or 2-piece slip yoke | Coil or leaf rear setups
| Blazer/Jimmy| Single-piece CV | Single-piece | Short wheelbase, compact setup
| Suburban | Single or 2-piece CV | 2-piece with center support | Longer wheelbase models
CV = Constant Velocity joint
Carrier Bearing = Center support for 2-piece shafts
🔩 U-Joints: Sizes & Types
Factory U-joint sizes vary depending on year, axle, and driveshaft style:
🧰 Common GM U-Joint Series in Squarebodies:
U-Joint Series Cap Diameter Width (Cap-to-Cap) Used On
1310 1.062" 3.219" Light-duty C10, some K10
1330 1.062" 3.625" Some 2WD rear drivelines
1350 1.188" 3.625" K20/K30, 1-ton trucks
3R 1.125" 2.556" Found in many stock 70s–80s GM
1410 (HD) 1.188" 4.188" Aftermarket upgrades
Many Squarebodies use a combination of 3R and 1310 joints. U-joint adapters or combo joints are common on swapped or upgraded setups.
🔧 U-Joint and Driveline Maintenance Tips
- Grease regularly if you have greaseable caps
- Check for red rust dust around caps = internal failure
- If you hear a “clunk” when shifting into gear, check for play at U-joints
- Grab the driveshaft and rotate/twist — any slop = worn joints
📐 Pinion Angle & Driveshaft Geometry
Proper pinion angle is essential for avoiding vibration, especially on lifted or modified trucks.
🔍 Types of Driveline Setup:
1. Standard Single U-Joint at Each End
- Used On: Most rear driveshafts, 2WD trucks
- Rule: Transmission output shaft and pinion yoke must be parallel at ride height
- If trans is down 3°, pinion should be up 3°
2. Double Cardan (CV) Joint Driveshaft
- Used On: Most front shafts and some rear 4WD
- Rule: Pinion yoke must point directly at the driveshaft (not parallel)
- CV joint absorbs angle; pinion must aim at CV
📐 Ideal Pinion Angle:
Setup Type Pinion Angle at Ride Height
Single U-joint Parallel to trans output (equal angle)
CV joint (front) Aimed at output shaft centerline
Lifted trucks Usually require pinion shim or cut/turn
2-piece shafts Carrier bearing must be aligned square
⚠️ Diagnosing Driveline Vibration
Symptom Possible Cause
Vibration under load Pinion angle too steep or too flat
Clunk when shifting or stopping Worn slip yoke or U-joints
Wobble at highway speeds Bent driveshaft or bad carrier bearing
Vibration only in 4WD Front shaft CV joint binding
Fixes:
- Check driveshaft balance
- Re-measure and set pinion angle
- Shim leaf spring pads (rear) or rotate axle (front)
- Replace U-joints or carrier bearing
- Make sure slip yoke is greased and seated
🔩 Driveshaft Upgrade Options
Brand Type Notes Price Estimate
Tom Wood's CV & custom shafts Made to order, strong, lifetime joints $350–$750
Adams Driveshaft Off-road CV shafts High-speed balanced, rebuildable $400-$800
Dynotech Aluminum/Steel Good for 2WD lowered builds $350–$600
OEM/Refurb Stock-style RockAuto, salvage yards $100–$300
For dual transfer case setups, custom shafts are usually required. CV joint shafts are a must for front setups with steep angles.
📏 How to Measure for a Custom Driveshaft (Front or Rear)
If you're running a suspension lift, dual transfer cases, swapped transmission, or aftermarket axles, there’s a good chance your stock driveshaft won’t cut it. Here's how to correctly measure for a custom-length driveshaft so you get it right the first time.
🧰 What You’ll Need:
- Tape measure (preferably 120" or longer)
- Angle finder or digital inclinometer
- Jack stands or ramps (truck should sit at ride height)
- Pen and paper
📐 General Rules for Measuring Driveshaft Length
🔸 Rear Driveshaft (Single-Piece Driveshaft)
Measure from the flat face of the transmission or transfer case output yoke (not the tip of the shaft) to the center of the rear U-joint cap at the pinion yoke.
Single-Piece Measurement Points:
Transfer Case Output Face → Center of Rear U-Joint Cap
🔸 Front Driveshaft (4WD Trucks with CV Joint)
Measure from the center of the CV joint flange or yoke ears at the transfer case to the center of the U-joint cap on the front axle yoke.
Double-Cardan (CV) Shaft Measurement:
Center of CV Flange → Center of Axle U-Joint Cap
🔸 2-Piece Driveshaft with Carrier Bearing (Long Bed Models)
Measure in two parts:
- Front Section: From trans/transfer case output face to center of carrier bearing mount
- Rear Section: From carrier bearing to center of rear U-joint at axle pinion
🔧 Additional Measurements to Include (if ordering from a custom shop):
- Operating angles (trans/t-case angle, pinion angle)
- Spline travel needed (for lifted trucks or high articulation)
- Yoke style and cap diameter at both ends
- U-joint series (e.g., 1310, 1350, 3R, etc.)
⚠️ Pro Tips:
- Always measure with the truck at ride height with full vehicle weight on the suspension
- Don’t guess the U-joint size — measure cap diameter and width
- If using a slip yoke, make sure it’s seated fully, then back out 3/4–1" for spline engagement
- Write down whether you have a flange, slip yoke, or fixed yoke at each end
✅ Summary:
Driveshaft Style Measurement Type
Rear, single-piece T-case output face → Pinion U-joint cap
Front, CV joint CV flange → Front pinion U-joint cap
2-piece rear shaft T-case → Carrier, Carrier → Pinion
Slip yoke setup Bottomed out yoke → back out 3/4"
🔚 Closing Statement
Your Squarebody’s driveline may seem simple, but it’s one of the most important systems to get right — especially once you lift, lower, or upgrade other drivetrain parts.
From U-joint sizes to pinion angle math, this guide gives you the tech to diagnose vibration, prevent breakage, and keep your truck smooth at every speed.
Need a custom shaft for your dual transfer case build? Reach out to Blazin’ Biddles’ Off-Road — we’ll get you what you need and make sure it’s right.