drive-line vibration

[Sheriff]

looking for a few clues re a vibration I get about 55-60mph, appears to me to be from driveline/tailshaft.   Had a look at universal joints, jacked car up, gave them a wriggle at both ends, they appear tight and ok.   Noticed that the front shaft into the back of the gearbox has some movement though. (oil seal does not leak as gearbox has only been in a year or so).   So, assume so far that the bearing inside the gearbox extension is worn and is likely to be the culprit.  Problem is the manual says that this bearing and extension are replaced as a unit.  Looks to me like the only solution is to have the bearing replaced maybe by an engineering works and reamed to size to fit the tailshaft?  Has anyone had a similar experience?    Thought other possibility might be the front engine mount.  There is some movement in engine when I give it a rock sideways though not much.  Mount is a bit oily from weep from timing cover and would be about 15 years old.
Any clues?   thanks, Mike.

[Royal]

  Hey Mike  I had this problem years ago , in behind the rear seal is a brass bush and in those days you could just buy the bush, it fixed my problem but as you say you will probably have to have one made or find a good extension housing somewhere, good luck
                                          Roy

[CraigA]

So you can feel it through your backside but not so much through the steering wheel?

When its vibrating does it go away when you take it out of gear?

Could be as simple as rear wheel balance. Swapping the front wheels to the back is a quick and easy check.

Or possibly an out of balance tailshaft.

[zulu]

Mike, check that the extension housing bolts to gearbox are not loose, I actualy had an extension housing crack many moons ago and it was preceded by a long period of vibration.

Also, you can send your drive shaft away to have it rebuilt and rebalanced, the mob I use are Metropolitan Driveshafts at Granville NSW, they have a 1 day service where they check and
R & R the unis, hone and replug the yoke, clean, paint & rebalance the shaft

Gary

[graham_fuller]

I had a similar problem and it was almost as Craig said, but it was a tyre actually out of round. Changed tyre and problem solved. Did the tail shaft bit before that though. The tail shaft shouldn't be a problem if there are no signs of it being hit and the uni's are fine.
cheers,
Graham

[Sheriff]

thanks for your suggestions.    will check the housing bolts.  Craig, have not tried it out of gear, but the vibration is through the seat, not in the steering.  Will also check out the rear wheel balance.   I am going to replace the front engine mount but from the movement I get at the back of the gearbox where the spline goes in, suggests to me that it is the worn bush.   thanks, Mike.

[Rod]

Interesting, I have the same problem. Just taken the motor out to do some front end repairs and have noticed two things. May not cause the vibration but need to attend to it anyway.

Firstly the front engine mount was stuffed.

Secondly the spigit bush isn't tight in the crank shaft and is rotating.

I will fix them up and tell you how I go.

Rod

[87 velo]

This probably won't apply to your situation, but just in case.  The angle of the output shaft of the gearbox should be the same as the differential flange.  The reason for this is that universal joints are not constant velocity devices (for an example grab your uni out of your socket set and run it through a large angle as you rotate it, it speeds up and slows down), so you need to run them in pairs and phase them correctly so that they cancel out any velocity fluctuations. 

The phasing is taken care of by the way the flanges are welded to the tail shaft (unless its a Commodore with a centre bearing and CV joint).  The angle of the output shaft of the gearbox is controlled by the mounts, although it can be altered with shims under the mounts. The angle of the pinion flange is controlled by the spring mounting pad on the axle assembly (assuming a leaf spring is used) I have seen these adjusted with wedge shaped spacers (like small lowering blocks), They are sometimes deliberately set up slightly out, as the axle housing tends to rotate slightly upwards when under driving loads.

Cheers Mick

[Sheriff]

Thanks, Rod & Mick.   Will see what happens when I get a new front engine mount in and wheels balanced.   Vibration is not severe, just enough to let you know it is there, and back off a bit.     Tried out my GPS the other day & checked the speedo.    I have 185/70 tyres on at the moment, and at 60mph am doing about 94kmh.  Am also in process of putting 185/80s on the rear to lower the revs a bit and fix the speedo variation.  I have a 3.55 diff.  From what I have read, the 185/80s are close to the diameter of 640x13s.  Found out also my Pathfinder's speedo reading is out as well.  At 100 only doing about 96.  Obviously has saved me a ticket or two.   Cheers, Mike.