Almost certainly not ABS. I don't believe you have independent rear suspension, so not a CV joint either.

If it's acting up while coasting in neutral and not touching the brakes then most likely it's driveshaft related. If you sense it's coming more from the front then either the forward universal joint or the driveshaft centre support (carrier) bearing would be my initial suspects. Most likely it's the U-joint as you didn't mention thumping, which is a classic symptom often associated with the centre support

The symptoms you describe all match vibration and noise issues when the forward driveshaft is having problems. It's not uncommon to have both the U-joint and the support bearing gone so you need to check both. If you replace the U-joint consider doing the centre support even if you're not sure it's gone as it's likely had to put up with increasing vibration in recent years. They're not that expensive and you're working in the same area. Mark all your driveshaft connection alignments before disassembly.

Also check the transmission mount. Shove the driveshaft up and down at the front so see if the transmission can clunk on the crossmember. If the transmission mount is failing then as the trans drops down closer to the cross frame it makes a slight change to the angle of the forward drive shaft and can make a failing U-joint or worn centre support bearing sound noticeably worse during braking and heavy acceleration. If you can't remember the last time the transmission mount was replaced then it wouldn't be the worst idea to replace it at the same time as you do the U-joint and centre support.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

Regarding your statements below:

"If it's acting up while coasting in neutral and not touching the brakes then most likely it's driveshaft related."

I meant braking while in neutral, no issues coasting in neutral without braking.

"If you sense it's coming more from the front then either the forward universal joint or the driveshaft centre support (carrier) bearing would be my initial suspects."

Definitely I sense this from the front at the brakes level, meaning the vibration is in that area.

This is an entirely new area of work for me. Everything related to the transmission and propeller shaft is just as it was when I bought the car from the dealer 28 years ago—no one has ever touched that part of the vehicle, and if they had, it would have been me. :)

Speaking of disc warping, would that be possible such a behavior out of the blue? Also, a warped disc would start to vibrate immediately as I hit the brakes, and not at the end of braking.

I found this video from this guy who describes what appears the same identical problem, start watching at minute 6:58 and this is what is happening to me:

https://www.youtube.com/watch?v=gRVtiRd7yVw

Thanks,
Alex

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

Hi Dave and everyone,

I took the car to my mechanic to confirm what I already suspected about the vibration issue—especially since it was happening even without braking and while in neutral, below 30 km/h.

The mechanic put the car on the lift, engaged the wheels, and at 30 km/h the driveshaft was vibrating severely. Long story short: it's the rear U-joint and the center support bearing.

I'll be disassembling everything myself, as I already know the propeller shaft part number is 9143292. However, I want to visually verify all the part numbers before placing any orders.

Also, another issue has come up—one that honestly left me speechless. But I’ll start a new thread for that, so get ready for some entertainment.

Alex

I am wondering where you are located not that it really matters. I'm guessing Europe?

Anyway...


I already know the propeller shaft part number is 9143292

You are not planning on replacing the entire driveshaft, are you? You only need to replace the worn parts unless there is obvious damage.

One very important thing to know is you must reassemble the shaft in phase. This is easy to do but if not done properly you will be removing the shaft again to correct the situation.

Before you take the shaft down look for the arrows imprinted on the two parts of the shaft. They may be hidden by years of grime. You can see them in the exploded diagram below. On reassembly make sure they are pointing directly at one another or you will experience the same sort of vibration you are already familiar with.


However, I want to visually verify all the part numbers before placing any orders.

You will want to get the correct parts, of course, but I don't think you will find any part numbers on any of the parts in question. There will be two different sizes of u-joints. The forward (unless there is a flex disc instead) and middle u-joint are the same part. The rear u-joint is larger. They should have a grease fitting and you will want to lubricate them from time to time. I have always preferred to remove the zerk replace it with a plug between lubes but that is not a requirement.





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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

Dear Metallo,

Hope you're well and stay so. Glad to hear that the vibration source has been found.

I recall a long-ago post, from which I learned that the bolts - that secure the driveshaft to the transmission output flange and to the rear-end flange - are used to balance the driveshaft. So, when removing the bolts, number each one to its position. If this is done before disassembly, the bolts can be replaced in exactly the same places that they were, when the car left the factory.

Rather than relying on applied markings (e.g., paint, that can rub-off), I'd use a pointed punch to mark each hole in the flanges and each of the bolt heads, e.g., one "dimple", two "dimples" etc. Put into a plastic bag each set of four bolts. Label each bag according to the flange to which the bolts belong, e.g., "front", "rear".

I don't recall that the nuts need to be so marked, but it might be best to do so. That will ensure that after the U-joints and center bearing are replaced, the driveshaft will be as it was, when it left the factory.

Hope this helps.

Yours faithfully,

Spook

If the car has a u-joint at the differential (some of the 900's had CVs at that position) the u-joint could be a bad. This can happen if they have not been lubed periodically although some u-joints don't have a provision for that. When they go bad the car will shake violently. Not sure if a bad CV would exhibit the same behavior.


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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

Hi,

Thank you for sharing your thoughts.

So, it is not the ABS, I removed the fuse (24), but the issue is still there.

If the problem is the CV joint or the U-joint, is it possible that the car makes more noise when going downhill without touching the accelerator? For example, on the highway, I had long downhill stretches, so when I was going downhill with cruise control on, without touching the accelerator, I noticed that the car was much noisier than usual. But it didn’t seem to come from the engine — it was hard to tell exactly where it was coming from because of the speed, the tires, etc

Also, should either the CV-joint or U-joint be the problem, why would it manifest only when the car is about to stop?

Finally, how can I verify this once I am under the car? Is it something obvious and visible at naked eye or is the driveshaft supposed to wiggle or so?

Thank you,
Alex

The noise you mention suggests a dry (bad) center driveshaft bearing. That happened on my 240. You can check this by safely lifting the car as suggested. Also check its mount for damage. Both should be replaced if that indeed is the issue.

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Will I buy another Volvo??? We'll see....

My experience is limited to u-joints so let's assume for the moment that's what we are dealing with.

I would have to hear the noise you're describing. It may or may not be related.

I don't know how to answer your second question other than to say it's just physics. What I don't understand is why you don't have this on first accelerating.

The best way to examine the u-joint would be on a garage lift but I suppose you'll be doing this at home so please take all necessary safety precautions. Chock the front wheels both in front of and behind them. One of the rear wheels also. Set the parking brake and put the car in neutral. Raise the other rear wheel. Support that side of the car with a jack stand under the axle tube. Now release the parking brake. Rotate the raised wheel and observe the u-joint at the differential. If the u-joint is bad the end of the driveshaft will be in an eccentric orbit around it's normal axis. If the driveshaft rotates normally on it's axis you might want to take a close look at the u-joint. A dry joint may have rust emerging from under the bearing caps.

I apologize for the condescending safety lecture. It is done just in case you are new to this sort of endeavor. Please be careful when working around or under a raised car.


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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

Thank you, Bulletproof (not sure what your real name is) :)

I am not a newbie, but believe it or not, driveshaft and transmission have never been touched since I purchased this car 28 years ago, so it is new ground to me.

Right now I am busy to identify all the parts in VIDA to familiarize with them and their names.

Usually, I lift my car on cribs, which give me 2 ft of clearance, that is how I do my work when removing the exhaust.

If I put the car on cribs (safer), in neutral gear and I spin the propeller by hand, would I still be able to see if anything is wrong with the u-joints or the central bearing?

Thank you,
Alex

(not sure what your real name is)

It's Don.

driveshaft and transmission have never been touched since I purchased this car 28 years ago

You should definitely replace all drive shaft u-joints and the center support bearing as suggested elsewhere in this thread. The front joint may be a flex disc. If so it may be okay. In my experience the original factory items wear like iron. But definitely inspect it. Others who are more familiar with the 900 please weigh in on any of this.

If both rear wheels are on cribs you won't be able to turn the driveshaft. One of them has to be free to spin.


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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

Pulling the ABS fuse is worth a try. But doubt that is the problem.

Don’t have a specific answer for you. If it were my car I would check all relevant steering and suspension parts you haven’t already checked. What about the lower steering shaft u-joint?

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Will I buy another Volvo??? We'll see....

Hi,

I fully agree with Bulletproof.

Just to add, when you're rotating the rear wheel you should be able to feel the point where the resistance increases. That point will coincide with the drive shaft making it's jump.

When it happened to me, coincidentally at the end of a long trip, I found the rear fully seized and the middle one getting stiff. There was no rust on the bearings, but they were both dry as a bone.

Peter

Hi Peter,

Thanks for your feedback.

When you say 'when it happened to me', did you experience the same vibration I have described, at the end on the braking only?

Or are you talking about a different issue that led you to change your u-joints?

Thanks,
Alex