How To Measure Drive Shaft Angles
Slopes vs Angles (How We’ll Use the Terms Here)
People often use the words slope and angle interchangeably, and that’s fine. For the purposes of this discussion, here’s how we’ll use them:
- Slope: the relationship of what you’re measuring to flat ground (the horizon).
- Angle: the relationship between the driveshaft and whatever it connects to (transfer case or pinion/axle).
The math is just finding the difference between slopes to figure out your joint angle. For example, if your driveshaft slopes down 20° and your transfer case slopes down 5°, the angle is 15°. If the transfer case slopes up 5°, the angle is 25°.
Tools You Can Use
Option 1: Angle Finder
You can purchase an "angle finder" at most hardware stores for about $10. Look in the tool department near the carpenter’s levels. It will have at least one flat base, a circular face with graduations around the perimeter, and a weighted plumb bob in the center.
Option 2: Our Free App
Pro Tip: Don’t want to buy a tool? Use your smartphone instead.
Download the Driveline Wizard app which includes a built-in angle tool and calculator:
How to Measure Slopes
1. Driveshaft
Place your tool right on the drive shaft. If there is no drive shaft, you can simulate it with a piece of pipe or a string line. For our photo we used a bungee.
2. Transfer Case
Measure off the output yoke or flange. Make sure you’re on the flat machined edge of the yoke. Any flat machined surface on your transmission, transfer case, or differential will be either perpendicular or parallel to the center-line.
3. Pinion / Differential
You can measure off the yoke or flange as above, or bridge your tool across two vertically spaced differential cover bolts.
Making Sense of Your Numbers
Depending on how you orient your tool, you may end up with different numbers. Example: if your tool says 83, subtract from 90 → call it 7. If it says 381, subtract 360 → call it 21.
Typical ranges:
Transfer cases: 0–10°
Drive shafts: 10–40°
Pinions: 0–30°
Example Video
Still confused? Watch this quick walkthrough:
Quick Reference Chart
Although our experience shows that measuring is the most accurate way, you can also use this chart for a rough guide to how rise and run affect slope.
FAQ: Will Rotating the Pinion Starve Bearings of Oil?
This is a common concern. However, once you look at how oil circulates, you can see that as long as the correct amount is in the differential, lubrication won’t be an issue. Watch the video below: