How to Measure a Driveshaft
To obtain an accurate measure for any driveshaft, the weight of the vehicle must be resting on its axles. Measuring for a driveshaft while the vehicle is on a lift with its axles suspended below will result in an incorrect measurement.
Single Piece Driveshaft
Measuring a single piece driveshaft starts with identifying the connection points of the shaft. Start from the transmission side and measure between those two points.
- Transmission Input Spline – Measure from the end of the splined shaft exiting the transmission sleeve.
- Pinion Yoke – The surface where the U-bolts or bearing strap bolts enter the yoke, mark where the centerline of the U-joint cap would sit. Measure from this flat surface.
- Flange – Measure from the flat surface at the end of the flange.
Multi Piece Driveshaft
As with a single piece driveshaft, a multi piece shaft starts with identifying the connection points. Measure the length from the transmission connection point to the center of the bolt hole for the carrier bearing. Then measure from that same point to either the next carrier bearing bolt hole or the end connection point, depending on the number of driveshaft sections.
How to Remove and Replace U-Joints
DISCLAIMER All driveshaft repair should be done by a qualified technician. Failure to do so could result in damage to the vehicle or personal injury. Safety Glasses should always be worn.
The first question to ask is: Has anything changed recently? Tires, shocks, lift kit, motor mounts, etc. Next, remove the driveshaft. Move the u-joints back and forth in all directions. If they feel loose or gritty, they need to be replaced. Spin the carrier bearing. It should spin smoothly. Check the tube for damage.
Snap Ring Style
U-joints can be removed by removing the snap rings either inside or outside type. By using a specialized tool or leveraging the opposing cross on a heavy duty vice and striking the curve of the yoke between the opening of the cap and the tube. This will drive the cap up and out of the yoke. Repeat this process for all caps.
Note: You must be careful to not hit the tube or the surface around the cap. Doing so could result in the need to replace the yoke or tube, which can be costly. Do not use a vice on the tube of the driveshaft.
Some driveshafts come from the manufacturer with nylon injected into the yoke that surrounds the cap of the u-joints. This holds the cap in place, and must be removed prior to the removal of the u-joint.
If the caps are retained by nylon injection, there will be a plug as shown in the picture. This should be brought to a qualified technician for removal. The generally accepted method for the removal of the nylon injection caps is to heat the yoke around the injection plug. If too much heat is applied, this can destroy the yokes ability to function properly. Once the heat pressurizes the injection, the plug will release the contents thereby removing the retention mechanism of the u-joint caps.
Note: Driveshafts with nylon injected u-joints should be rebalanced as the replacement joint will seat differently causing a potential shift in weight around the centerline of the shaft. This can cause a noticeable vibration.
Some driveshafts come from the OEM with staked in u-joints. These joints have a portion of the yoke pressed over the cap as shown in the picture. Many consider these joints to be non-serviceable.
The method generally used for removal is to press the u-joint cap through the stakes in each direction. Then to grind the internal surface of the yoke to a smoothed finish to receive the replacement u-joint caps. The ear of the yoke needs to be cleaned and properly surfaced to fit the inside snap rings correctly.
Note: If the surface of the yoke is ground too much or not in a uniform circle, the u-joint will not seat properly, causing a vibration.
After removal, clean the yoke and inspect for damage to the yoke. Clean the yoke where the snap ring seats to prepare for u-joint installation. Make sure you have the proper u-joint for the yoke.
Installing New U-Joint
Note: There are conversion u-joints for some OEM applications. These are used when mating two different size yokes. Please confirm the cap diameter and length for both sides of the cross.
When installing the new u-joint, it is convenient to align grease fittings (when present) for easier maintenance. Apply a small amount of approved grease to the inside of each cap. This will help to hold the needles in place along with lubing the u-joint trunnions and cross. Align the cross and cap, keeping a portion of the cross in the cap to insure the needles do not drop. Press the cap into the yoke, making sure the cap and cross do not bind causing the needles to drop into the cap. There are specialized tools for removing and installing U-joints that can be used, or you can use a heavy duty vice, arbor press or c-clamp.
After pressing in the cap, make sure you have pressed the first cap in far enough and install the snap ring. Failure to do this will cause the cap to slide back out when installing the opposing cap. When installing caps that require outside snap rings, you will need a punch comparable in size (Some have been known to use a socket and a vice) to press the cap past the groove and use a pair of needle nose to insert the snap ring. Press in the opposing cap far enough that you can seat the second snap ring. If not, you may have a needle down in the cap or your yoke is sprung. Your snap ring groove may also be damaged. You may be able to rotate the snap ring so the opening is at the damaged part of the yoke.
Once complete, the joint may not move, and it is necessary to strike the base of the yoke to release the U-joint.
Note: For inside snap rings, the snap rings must be connected to all caps (even those that are not pressed in). These are used as guides to properly seat the u-joint into the pinion yoke.