Driveline Shudder on 700 and 900 Series Volvos

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A common tech call we get here is regarding shudder, which occurs when pulling away from a stop. This problem is commonly mis-diagnosed as universal joints or rear end bushings. Most often though, this problem is related to the articulated driveshaft.

As the rear suspension travels up and down, the length of the shaft must change. This is accomplished with the splined fitting just behind the center mount. If the splined fitting is fully compressed, the driveshaft will be forced to the side as each knuckle of the universal joint passes the tightest point of it's rotation. This issue becomes drastically more pronounced with large loads in the rear of the car or with cars that ride low in the rear as a result of failed coils or self leveling shocks. It can also be a problem with cars that are lowered.

Start by taking a good overall look at the ride attitude of the car. Do not pay any attention to the wheel arch-es since Volvos always have lower rear arches than front. The most reliable way is to measure from the frame rails to the ground or from the jacking points to the ground. If the car sits lower in the rear it needs to be fixed.

Next have someone sit in the trunk or cargo area and survey the car again. If the car drops dramatically under this small load there is most likely a problem with the coils or the self-leveling shocks. Under acceleration the car will rock to the rear and fully compress the splined fitting causing a shudder.

Don't forget to inspect the driveshaft and transmission mounts for damage as well. A problem here will shudder without any help from other sources. If all these items check out well and the car still shudders when pulling away, take a look at the driveshaft and see if it is fully compressing.

While this problem can occur on any Volvo, there is a shade tree fix for 700/900 series cars. The keyhole style driveshaft mount on these cars can be shimmed up a few millimeters. This, in effect, lengthens the drive-shaft and prevents the splined fitting from compressing fully. This adjustment is frequently needed on lowered cars. If more than a couple millimeters are needed the driveshaft should probably be shortened by a driveline shop.