A damaged driveshaft can exhibit a variety of symptoms. A clunk that is heard when the transmission is shifted into gear is the most obvious. You can also encounter unusual noise, roughness, or vibration.
The engine, torque converter and driveshaft change in frequency as rpm changes. A rebuilt torque converter is often the cause of a vibration that is rpm-related.
To help differentiate a potential drivetrain problem from other common sources of noise or vibration, it is important to note the speed and driving conditions at which the problem occurs. Unfortunately, it is often difficult to accurately pinpoint drivetrain problems with only a road test. Expand the undercar investigation by putting the vehicle up on the lift, where it is possible to get a good view of what is going on underneath.
- Check the companion flange, carrier bearing, pinion shaft seal, and pinion bearing, transmission's extension housing seal and bushing, and the u-joints.
- Check the driveshaft for runout, or the amount that a part wobbles up and down or side to side when it is in motion.
Measuring driveshaft runout. Courtesy of Ford Motor Company.
- First, measure the runout of the driveshaft.
- Mark the high spot on the shaft.
- Then remove it and remount it at a spot 180° away on the flange.
- If the runout remains the same, the shaft is at fault. Otherwise, the flange is the problem.
- Check the phasing of the joints and their angle.
- To check their operating angle, use an inclinometer.
- Your findings from this test should be compared to specifications.
- Normally, if the angles are wrong, the rear axle has moved in its mounting.
- As a final diagnosis inspection point, check the entire length of the driveshaft for excess undercoating, dents, missing weights, or other damage that could cause an imbalance and result in a vibration.
- If no damage is found, the driveshaft should be removed and its balance checked.