Lifting Your Truck? What You Should Know About Drive Shaft Dynamics

Posted on: 26 February 2015

If you've decided to lift your truck for the first time, sorting out the different kit options and components can be dizzying. One of the things that many first-time lift buyers overlook is upgrading or lengthening the rear drive shaft that connects the transfer case to the rear axle. A drive shaft that's too short will connect at a sharp angle. This can cause your newly lifted truck to handle poorly. If you're familiar with where the drive shaft and transfer case are under your truck, you'll be able to measure for a new one on your own without needing a technician. Here's a look at the importance of upgrading the shaft and how to measure for the new one.

Why Does it Matter?

The geometry of your truck's suspension is designed precisely so that all of the joints, shafts, and springs work together. When everything is at the proper angle and height, the suspension rides comfortably and the truck responds well when you turn the wheel.

When you engage the four-wheel drive, the transfer case locks into gear and starts turning the rear axles in conjunction with the front. The drive shaft connecting the transfer case and the rear axle then begins to turn as well, because it is the sole connection between those two components. By adding any kind of suspension lift, you change the ride height and the center of gravity. This changes the angle of every suspension component. The fixed length of the drive shaft may leave it at a sharp angle, which can put more pressure on the shaft than it's made to handle.

When the drive shaft geometry is altered, it cannot respond appropriately when you turn the wheel. This can lead to handling problems including poor response. Over time, the strain of this improper angle can cause vibration in the drive train as well as excessive wear on the joints at either end of the shaft. Ultimately, it will cause drive shaft failure.

Measuring Your Drive Shaft

If you want to install a new drive shaft in your truck as part of your suspension lift, you'll need to measure for it after you install the rest of the suspension lift. This is vital, because that lift will determine the ride height and the geometry of your drive shaft installation.

Once the lift is installed, you'll want to jack up the truck and support it on the axles. Then, get underneath and locate the empty U-joint on the transfer case that's facing the axle. Measure from the flat outer surface of the transfer case to the flat surface on the axle differential. The differential is the "pumpkin", or the large round section in the middle of the axle.

Then, measure the distance across the U-joint cap, which is the U-shaped space where the drive shaft connects to both the transfer case and the axle. It's important to get this measurement right, because the joint that connects each end of the drive shaft has to fit properly for it to be secure. Use the measurements you obtained to order a drive shaft that's long enough and has a wide enough U-joint connection to properly fit in the suspension.

As you can see, the drive shaft plays an important role in your truck's lifted suspension. With your own basic understanding of the shaft and its function, you can measure for a new one and ensure that you maintain your ride integrity. For drive shaft questions or repair, call Turnersville Transmission Center.