Front Drive Shaft Considerations for Jeep Wrangler JL (No FAD)

Front Drive Shaft Considerations for Jeep Wrangler JL (No FAD)

While Jeep Wrangler JLs equipped with the Front Axle Disconnect (FAD) system can disengage the front driveshaft for improved fuel economy and reduced wear, those without FAD require careful consideration of the front driveshaft setup, especially after lifting the vehicle.

Pinion Angle: The Key to Smooth Operation

Both the stock Rzeppa-style driveshaft and aftermarket double cardan shafts utilize a single universal joint at the axle end. This shared design element necessitates proper pinion angle adjustment to minimize vibrations, particularly after a lift.

  • Why Pinion Angle Matters: Lifting a Jeep alters the angle between the driveshaft and the axle pinion. Excessive angles can cause vibrations and premature wear on the driveshaft and related components.

  • Double Cardan Doesn't Change the Game: While a double cardan shaft at the transfer case end offers improved articulation by accommodating larger driveshaft angle changes during suspension travel, it doesn't eliminate the need for proper pinion angle at the axle end. This is because the single joint at the axle end remains the critical factor for smooth operation, regardless of the driveshaft type. Whether you have the stock shaft or an aftermarket shaft, the correct specs for pinion angle are the same. Likewise, the operation of the universal joint at the axle end of the shaft is the same in both scenarios. See the photo at the bottom of this page for reference. The shaft pictured at the top of the photo is a stock shaft, the shaft at the bottom is an aftermarket double cardan shaft.

  • Steering Caster Considerations: Adjusting the pinion angle can affect the vehicle's steering caster, which impacts steering feel and stability. Finding the optimal balance between pinion angle and caster is crucial, as prioritizing one over the other can negatively impact overall handling and stability.

Aftermarket Driveshaft Vibrations

One common misconception is that aftermarket double cardan driveshafts inherently cause vibrations. While it's true that some experience vibrations after installing an aftermarket shaft, the primary culprit is often the increased mass of the aftermarket shaft.

  • Weight Matters: Heavier driveshafts amplify any existing vibrations due to the higher rotating mass. This emphasizes the importance of meticulous pinion angle adjustment and proper balancing of the driveshaft. This is especially true for 1350 series drive shafts due to the larger size of the upgraded components. However, despite the added weight of a 1350 series shaft we still think that the strength advantages make the 1350 series shaft the best choice. 

Recommendations

  • Post-Lift Adjustments: If you've lifted your Jeep JL, have a qualified technician check and adjust your pinion angle to ensure smooth operation and prevent premature wear.

  • Caster Optimization: Work with an experienced alignment shop to find the best compromise between pinion angle and caster for your specific lift and driving style.

  • Driveshaft Balancing: Ensure any aftermarket driveshaft is properly balanced to minimize vibrations.

By understanding the factors that influence front driveshaft performance in your Jeep Wrangler JL, you can ensure a smooth, vibration-free ride and maximize the longevity of your drivetrain components.