Rebuilding driveshafts rates near the bottom of our list of fun things to do with a Volvo. There are few other operations on the car that require the same combination of brute force and finesse -- the brute force to drive the U-joint bearing caps in and out; the finesse to keep their needle bearings in place while applying the brute force.

That being said, the job is straightforward enough to do at home if you have a sturdy bench vise, a suitable length of something to use as a drift (an old deep socket works pretty well) and several pounds of sledge. The Haynes manual "how to" is adequate for the most part, but there are a few traps for the unwary.

Trick #1
Both segments of the driveshaft were once balanced at the factory, and it is important to reassemble them in the correct position -- presumably, the way they were before being taken apart. Haynes suggests making scribe marks on the flanges to use as a key upon reassembly.

That's just great -- until you drive out the old U-joints, which leaves you holding three flanges, two pieces of shaft, and no clues about how it went together. So, don't just mark the flanges, mark the shafts, too! The relationship between the shafts is actually more important than whether the flanges get on 180 degrees out or not.

Of course, if you were getting vibration back when your U-joints were good, there's no point in this -- take the whole mess to a driveline shop and have them balance it right.

Trick #2
U-joints are dimensionally symmetrical, and can be installed into the yokes in any one of four 90-degree rotations. Unfortunately, two of the four are wrong -- and you won't know it until you've gotten the whole thing pounded together and the grease fitting installed. If you land on the wrong side of this 50 - 50 chance, the grease fitting will limit the movement of the joint.

If you take a close look at the front end of the forward shaft, you'll note that there is a slight cutout on the yoke (sometimes also a slight depression on one side of the shaft) -- if the yoke is pointing up, it's on the left. When you fit the U-joint, the threaded hole for the grease fitting must be closest to the cutout. This is identical on both sides of the shaft, and on both ends of the rear shaft. These cutouts are easy to overlook, but they make all the difference.

If the new joint has the hole offset, it goes nearest the shaft, not the flange. Pay attention -- you really don't want to have to drive your new joints back apart for a second try.

Yes, we found this out the hard way.

It's easiest to grease the new joints before assembling the driveshaft back onto the car. The front shaft and its support bearing / bushing (there are several styles) goes on first; you can then fit the splines on the rear shaft into the front so the marks line up.

In the correct orientation, all three yokes lie in one plane. It's still possible to get the two shafts 180 out, though, so make those marks easy to see.