Determining the Causes of Vehicle Vibrations

Driveline Vibrations

Driveline vibrations are probably the hardest things to diagnose next to intermittent electrical problems. In many ways, you’re left guessing and you end up throwing parts at the problem. Here are a few tips if you suspect your vibration is coming from the driveline.

First, address the tires and tire balance. If you have a vibration at speed, these are the first places to look. If you have good tires and they’re balanced, it might be time to look at the driveline if you still have a vibration.

If you have an automatic transmission, start by checking the fluid level and condition. If the fluid is low, top it off and recheck for the vibration. If it’s gone, consider yourself lucky and try to find where the fluid went.

If you have a manual transmission, check the operation and condition of the clutch. A slipping or glazed clutch (a condition caused by overheating) can cause vibrations sometimes. Here’s a video on how to check your clutch operation.

If you know your automatic transmission or clutch is good, let’s move onto the next step. With front wheel drive vehicles, you normally have two axles with CV joints on the inner and outer part of the shaft.

Sometimes inner CV joints have issues and cause vibrations. These can be very hard to track down. The symptoms usually occur driving at speed, say 65 to 70 mph, and sometimes as low as 55 mph (but not often at that speed). You might notice that if you turn the wheel slightly to one side or the other, the vibration gets worse (or better if it’s an inner CV joint problem). Once you turn the wheel straight again, everything’s fine. This normally tips me off to an inner CV joint problem.

Finding out which side it’s on gets a little tricky; I’ll admit that it’s mostly a guessing game. You can push up on the axle near the inner CV joint to check for play. The side that has the most play is likely to be the bad CV joint. However, this is not always the case. You can’t repair these; you need to replace them. I’d recommend replacing the entire axle before attempting to replace just the inner joint. Axles, for the most part, are inexpensive these days, and replacing just the inner joint, if you can even find one, just isn’t practical. If you replace one side and your vibration is still there, replace the other side and recheck. I did say this turns into a guessing game; I wasn’t kidding. Here’s are some videos on axle replacement and CV joint replacement that you might find helpful.

Rear Wheel Drive Vibrations

These are even more difficult to track down than FWD vibrations. It’s very difficult to find the source of a driveline vibration in a rear wheel drive vehicle. As with FWD vehicles, make sure your tires and tire balance are good before you look to the driveline.

Three things can cause a vibration here: a bad U joint, a bad center bearing, or a differential problem. I suppose you could also say the driveshaft itself, but I would put this at the very bottom of my suspect list and eliminate the previous three first.

As with FWD vibration problems, it’s really a process of elimination. Start with the cheap, and work your way to the more expensive. Inspect the U joints first. Look for loose ones or orange dust around the bearing cups.

This indicates a lack of lubrication, and likely means the U joint is on its way out. If you find one of these, replace it, and then recheck for the vibration.

Center bearings can be a little tougher. For those, you can also check for looseness and orange dust.

If that’s what you find, replace it and recheck for the vibration. The center bearing might be part of a complete axle assembly, so you might want to check the center bearing first if you suspect a problem, as the new axle should come with new U joints.

Differential vibrations are almost always caused by a lack of lubrication. Sometimes water gets into the differential. If that’s the case, make sure your breather is intact and not in a place where water can get in.

If your differential is low on oil or has water in it, get the water out, top off the fluid and recheck.

Don’t have a lot of hope here. If you have a vibration and one of these conditions, it likely means that your differential bearings are bad and need to be replaced. Differentials are normally either good or bad. As for a limited slip differential, make sure you put the correct fluid or fluid additives in it. If you don’t, it can cause a vibration or damage to the differential.

I see more issues with differential vibrations on limited slip differentials than anything else. This is due to the clutches in the differential not being lubricated properly. If you don’t use the proper lubrication in a limited slip differential, you can damage it and its components. You can identify a limited slip differential in a couple of different ways. One way is to look for a tag bolted to the outside of the housing that says it’s a limited slip.

The other way is to raise the vehicle and spin one wheel. If the opposite wheel spins in the same direction, it’s limited slip. If it spins in the opposite direction, it’s a conventional differential and you don’t need to worry about putting in additives or special fluid.

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