Hi Alex,

That's a good video and if his description matches your symptoms then you're almost certainly on the right track.

First time working on the drive shaft will be a bit of an adventure and may need a few special tools. Think about taking the shaft to a shop and have the U-joint(s) and/or support bearing pressed out and reseated rather than trying to beat them out with a hammer and drift, possibly doing damage. The 140/240 supports you may see written about were a slightly different design and more prone to early failure.

The source of vibrations can be mildly deceiving. If the vibration is at the front end, such as warped rotors, worn suspension bushings or worn front bearings then I would have expected you to have sensed it coming up through the steering column, which you say you didn't.

There are a few tell tale signs for this being a brake or wheel problem, such as unevenly worn "warped" rotors, which is why I immediately dismissed that as a prime suspect for you.
a) The longer you drive, the hotter the brakes get, the more the rotor metal expands to exaggerate the problem. Nearing the end of a long trip, your brake shudder/vibrations/pulsations would be noticeably worse as the brakes get hotter, such as snubbing the brakes down a long steep hill.
b) When you lightly touch the brakes at very low speed, such as coming to a stop slowly, you will notice a hint of pulsation/hesitation that is in sync with the rotation of the wheels, not the drive shaft or engine revs (putting it in neutral will make little or no difference if it's brakes).

Seems like you're well aware of this, but as others have mentioned safety I'll chime in with my two-bits. Getting additional height to work safely under the car without a hoist means being doubly careful about having the vehicle very stable up on ramps or jack stands. I always jack the car up evenly left-right so it isn't tipped at an angle and absolutely always lean on and try to heavily rock the car before crawling underneath.

In that video, Smitty said he's had a few bad experiences with Rock Auto fitments with Volvos. In my experience, their fitments for name brand stuff are generally good, but maybe not so much their economy aftermarket parts. I've not had any problems with Rock Auto in the dozens of orders I've placed with them over the years, but then I always double check the fitments of the parts they list using the manufacturer's part number.

Wishing you good luck...

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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now