Hi everyone .. I hope I can get an answer to my problem.

My center support for the drive shaft went bad .. it has been bad for some time .. it was growling under load .. so, I pulled it and put in a new support and bearing ... on this year model the support goes one way and you have to remove the bearing to replace it .. so while I was doing the support I was forced to do the bearing as well.

I have a vibration now at about 45mph and it will almost go away at 60 mph ... the deal is I can not live with this and I didn't have it with the way it was before I did the support and bearing.

The drive shaft is in phase as it was marked before removal .. so it is not out of phase.

What has gone wrong with this project ?

I have read before that having a bad support for a period of time with mess up the Transmission mount?? I was wondering if this is true and now that the shaft is fixed it is making a vibration due to a bad trans mount?? I looked at it while under the car and tried to pickup on it to see if it was bad .. doing it this way I didn't see anything bad ... but I would like some advice/help before just throwing more money at it.

Thanks in advance for any help,
Dave

 

Well, never heard of it effecting the trans mount. It will cause the tail shaft to start wobbling which can cause vibration. The only other things that generally will cause vibration are stiff U joints or less than flat flange mating surfaces. So, look at the flange mating surfaces and make certain both sides mate flat. A ding from a hammer can make them almost lay flat but will need to be filed down to be dead on. A stiff, notchy feeling U joint will not be able to immediately compensate for slight variances. The front and rears can be checked off the car (drive shaft removed)a bit easier than on the car. A good U joint should have no slop and move fluidly without any catching at all. To check the tail shaft, just try to move it side to side and up and down. Should have very little play.

 

Swift - I read some place that a bad support in time will wear the trans mount .. I have not taken my mount (Trans) off to look at it .. but in the morning I plan too take it apart and see what's with it .. laying under it I can move the trans up and down some .. not much but I can see the center mount bolt looks like it is moving up when I do this .... perhaps the mount has gotten soft over the many miles (200,000) it is original. The u-joints felt free when I had the shaft off .. but something has changed ...

Since the support and bearing have been changed my other symptoms have gone away .. no more Growling when carrying a load .. but I am now left with this vibration that I never had. All parts have been gotten from FCP and are good... had I gotten stuff from the local parts house I may have wonder if bad parts are causing my troubles.

 

Volvo mounts are designed to shear under impact. As a result, they are shot at 50k so...

 

WOW !! that would make mine way over due ... car has 200,000 on it and i am positive the trans mount is original .. might not hurt to get a set of motor mounts for her ... they seem fairly easy to get to ... I've also heard of mounts that collapse .. I'll report tomorrow what I find with the trans mount ... I'd pay 100.00 extra if it takes the vibration out ... this is worse then having a dog with fleas

 

I just did this. After 100k mi of complaining, it was time.

When I threw mine back in I put all the mounting bolts in place but did not tighten them down. They were just snug enough to be moved with a little effort. I spun the shaft around a few times and made sure that it was all in line. While tightening, I took special care to make sure that the tightening did not twist the bearing at all. Maybe misalignment is a cause. I would have a tendency to think that the other mentioned scenarios are more likely, but this should be easy to check.

 

UPDATE :

I got back under today and replaced the Transmission Mount (money well spent) it needed one ... mine was all smashed down and I could see the difference in height .. BUT, this DID NOT solve the troubles, BUT ! while I was back under I looked closer at the rear shaft ... when I did the center support I only pulled the front drive shaft ... so upon looking at the rear shaft and twisting on it the U-Joint closest to the support has much movement in it .. I could twist the shaft and it would move a good bit before catching the other part of the yoke ... NOW, Question, this is me thinking so help me with my crazy thoughts ..

Thoughts - I replaced the support and bearing, 100% bad ... I got the vibration after installing .. now, with the worn support the bad u-joint was not as noticeable but now with a new support and everything being tighter - do you all feel my vibration is caused by this U-Joint??? seems to me like logic .. either way the joints are getting replaced tomorrow .. I am just gathering thoughts here so I can sleep tonight before being disappointed tomorrow when I do change the joints and still have the vibration ... I am going to change all 3 joints .. figuring if one is that bad the others have to follow soon.

 

your thinking is sound. the center supprot was more than likely taking the brunt of the vibration, and now that it's gone, it travels to the next weakest link.


look at it this way: the u-joint has play that it shouldn't have, so replacement is a good thing, whether it takes out the vibration or not.

 

Update (2) - changed u-joints ... vibration is still there .. it's more of rumble type vibration.

I checked one thing that I have always noticed about the car to see if it is still acting up - if I put the car in reverse and punch the gas .. it makes the very same rumble/vibration ... NOW .. what ever is causing this maybe the very rumble I am getting with tightening the drive line up .... what would cause a rumble/vibration when flooring the gas in reverse? are there some kind of bushing that would cause all these symptoms? I am lost where to go next and can't keep throwing funds away ....

 

Does the car sag in the rear? If it does it may cause the drive shaft to be out of alignment.

 

It may have some sag due to age ... I really have no idea what to measure it by .. I know when it was loaded with 4 adults and some rear cargo you would have to be easy on the gas starting out or it would growl or make a noise as if someone was beating the floor with a rubber hammer ... but unloaded it was fine.

As I said in my last post I have heard about shimming the support ... I dont know much about it .. I can vision shimming it up but i have no clue as to down unless you would shim the cross member ... up is easy just add a washer under it ... any thoughts on this.. or experience ?

 

How about the engine mounts?

 

Vibration is gone ... I changed motor mounts which it did need ... but the vibration was still there .... I ended up getting another driveshaft .... 100.00 used and put the whole thing in the way it was and now the car is great again .. I have NO CLUE what was the deal ..... unless my original shaft was bad and I could not feel a vibration until I replaced the center support .... hence .. this tightened everything up and the vibration showed up ... either way ... I am good to go again ... Thanks everyone for your help !!

 

Glad it is all good now!

 

Sweet!!

 

I also experienced excessive drive-shaft vibrations (and resonances) after replacing the worn-out center drive line bearing & rubber support.

Replacing the u-joints and then the engine and transmission mounts all helped a little – but drive-line resonances (45-55 MPH) was still very noticeable. Last resort – balancing the drive-line did not resolve anything – driveline was already in “perfect balance”.

Final fix - modifying the mounting plate where the center bearing is fasten to (resonances has now disappeared ). Mounting plate is now “suspended” in rubber mounts -- moves and down (1-2 mm) applying moderate manual force. Lateral movement is minimal – isolated by soft nylon bushings (cut from a nylon hose). Rubber shims 1/8 inch thick inserted on top and bottom of mounting plate to cushion vertical movements/vibrations. Four metal spacers (15mm long) - fastened via four longer screws, oversized 5/16” shims plus star lock-washers keeps plate securely in place.

E Hansen, Morgan Hill, CA
94 Volvo 940 & 65 P1800