Good Vibrations?
 

Larry,

Do you have each tire balanced on both sides?

I see it's a manual transmission (I'll trade ya :D). Have you checked rear trans bearing play with the trans in neutral? Just wondering if you have some play there, allowing slight vibration that increases as the speed does (differential bearing also is a suspect).

I have experienced this on other cars, such as hot-rods in the past with carrier bearings in the driveshaft, and it turned out to be the rear transmission bearing play. All that power hitting the rear bearing after dumping the clutch in a big block [383 magnum] dodge 4-speed:D.

Maybe this will help someone, even if it's not your current problem. Good luck with it! :)

I Know This Is An Old Topic
 

But, look at this for Volvo related driveline vibration problems and solutions. I did a search on transmission and pressure so I could get info on the broken spring problem and saw this thread.

http://www.brickboard.com/FAQ/700-900/Driveline.htm#DrivelineVibrationDiagnosis

Larry,
Would this fix also apply to an automatic transmission?

Yes, this would apply to an automatic driveshaft as well. If the problem is that the u-joint is worn in one spot, the shim between one side of the carrier bearing and the body will greatly reduce, if not eliminate the vibration.

Good luck,

U joint health determination
 

Larry/ Others,

I'm finally getting ready to pull my driveshaft. I tried Larry's suggestion and in my case it didn't work, so off to the next most likely culprit.

I have a new center bearing and flex disks if needed. How much "play" - rotational I would guess - would be acceptable in the u-joint? Are there other parameters to consider such as smoothness of operation in the bearings? The last u-joint I changed was on a '70 Torino 8).

Chuck

Chuck, unless you have a machine you can bolt the driveshaft into and balance I would use caution replacing the u-joint at home. It has to be "centered" in the yoke. As you will find it is pinned and not clipped like the Torino. I would recommend calling Earl at Drive Line Service of Atl (404) 361-0475 and arrange to ship it to him for rebuilding/balancing.

The u-joint is not servicable as most are. The driveshaft shops like the one Jim suggests, will put in an entirely new joint.

To answer your question about inspecting the joint, both axes should rotate smoothly. Most likely you will have a "notch" or detent as you flex the joint in both axes. This is what the relocation of the carrier will hide.

Since that didn't work, you should inspect the flex disks and the carrier bearing including its rubber mount. The front flex disk fails more often because it is subjected to lots of heat. The rear flex disk deals with no heat, so usually is okay.

Also when you remove the shaft to inspect it is common for it to slip apart into two pieces. There are marks that will show you how to realign. There is a raised knot on one piece that aligns with two raised knots on the other piece.

Good luck,

Thanks!
 

Folks,

Thanks again for your expertise!

I tried an interesting experiment of couple of weeks back to determine the source of vibration... but with no success. First was Larry's suggestion of offsetting the center bearing support, no-effect. Then I jacked the car up and then put it down on jack stands under the rear shock mounts. My theory was it would keep the axle half-shaft orientation closest to driving as opposed to having them droop downward.

The family was away so I had to try and look for the vibration alone. I first tested taking the car up to 50-55 on the jack stands. It had the vibration appear, but no sense of un-steadiness on the jack stands while running. I did have secondary jackstands and spare wheels under the body as well for backup.

Being alone I used a my camcorder to record front and rear driveshaft and each axle. Curiously there was no discernable vibration to be seen. It could be felt. The camera was about 3-4 feet away but I didn't see any vibration shown in any component. At over 260K now I expect it is worth trying center bearing and flex disks anyway.

I hope to have an update in a week or so.

Chuck

That is a good idea on putting the camera under there. I deal with rotating equipment and vibration analysis all the time and I would suggest using a stobe light set at the rpm of the d'shaft with that camera. We use strobe lights to inspect/check out rotating shafts and couplings all the time and I have to keep the thought in the back of my mind that just because what you see is sitting still - that baby is hauling. If there are driveshaft issues you will see them with the stobe light.

I just thought of this. Chuck, what exactly is it doing? If you are fine up to like, 40 mph, and then it starts vibrating then I would suspect the d'shaft. Otherwise, it may be something else. What are the symptoms?

Outstanding. There's nothing that substitutes for scientific analysis.

I would NOT just replace flex disks and carrier bearing components without first inspecting them. I realize that it is a pain to pull down the exhaust to accomplish this, but just throwing parts at the problem will most likely be a futile exercise.

Drop the driveshaft and rotate both axis of the u-joint. If they are not smooth, get a rear shaft or have u-joint replaced. Inspect flex disks at that time and rotate the carrier bearing to see that it is smooth and that the rubber is not tattered.

Good luck,

Just a thought though.

When you have your driving wheels off the ground, the drive line is unloaded for all practical purposes. This would change the behaviour of the system (for vibrations) compared to a loaded system like when you have the wheels on the gound and the vehicle is being driven.

Actually, due to the fact that the u-joints, flex disks and carrier bearing, when loaded, probably have slack taken up, in many cases, unloading the driveshaft would actually amplify the vibration, but not always.

Have a great day,

More thoughts
 

Thanks again for the inputs. I thought the load may make a difference as well. I actually contacted a local dyno to see if I could run the same experiment under load. I was thinking large mirrors and lights to see underneath..... haven't had the time yet so I decided to start with a few reasonable parts.

The symptoms are vibration starting around 40 up until 65-70 then it reduces. The vibration is felt in the center of the car. I have replaced tires and wheels and rotated several times in the last year and no change. Two separate, fairly competent shops have briefly looked at it with no conclusion - that was my hysterical differential post a while back. The camera did record a squealing sound starting around the same speeds... may again point to the u-joint. The mechanic may not have dropped the shield and the sound transferred back toward the differential.

I decided to start with cheap/simple and see how things progress. The offset center bearing was an easy try, but in this case it didn't improve things. As I said, I am at 260K plus now so a center bearing may be worth a try. While the shaft is down I am most interested in the u-joint as recommended. I think my SDL is fortunate in not having to remove the exhaust ( single all the way back). I got the shield off before without removing the exhaust, so I'm optimistic.

Any idea on the turn-around time for the Atlanta driveshaft guys. I've done more Mooresville - Atlanta and back in the same day trips than I can count. If they can fix it in 4-6 hours I may just drive it down ( in another car).

Thanks for all the assistance and I will certainly post any results.

Chuck

Yes, it's the 124 chassis that requires exhaust lowering for driveshaft access. It's not too tough to do this, but it's a real pain if you need access to the shaft more than once.

Without the exhaust in the way, it shouldn't be a big deal to pull the shaft as long as you have a way to safely raise the car.

Good luck,

Chuck
Call em at Drive Line Service and ask that question. It may be doable if you pre-arrange it.
I have always just dropped them off and then they UPS'd it back to me. The last one they did I dropped off on a Monday and had it back by Thursday.