Annoying vibrations

[TTM]

Hello,

For some time now my car has developed subtle but constant vibrations that seem to find their source somewhere at the back end, and move their way up to the driver's seat. Rather appropriately we could call this phenomenon a pain in the derrière.

I rebuilt the rear axle recently with fresh standard bushes everywhere. Geometry settings were checked afterwards. Wheels and tyres are balanced.
At about 190k miles the torque tube is not so fresh but mated to a 70k miles old gearbox the pair sound like they still have a lot of life in them.

At this point I strongly suspect the gearbox mount and/or the half shafts and don't think they have ever been replaced.
I have not checked the gearbox mount, and half shafts don't feel like there is any particular excessive play in them. Rear wheels bearings may be original too but the alignment guy reckoned there was no play in them.

Any suggestion on where to look at for hopefully a definitive diagnostic?

Thanks.

 

[Riverside]

Engine & gearbox mount problems would make the whole shell feel rumbly, and are generally bad while stationary at idle.

Whenever I've had roughness from the rear it's always been from CV joint wear, even when other stuff has needed doing too.

hth.

 

[zcacogp]

Put this on the stereo and turn the volume up ....

http://www.youtube.com/watch?v=nC2gZMNkyJo

(Sorry, not my most helpful post ever but it needed to be said! [])


Oli.

 

[andy watson]

80% sure it will be CV joints, recently changed all 4 on mine = no vibration

 

[George Elliott]

Oli.....[]

TTM, have you put the Drive Shafts back on the same side they came from? they wear according to direction, and may not run smoothly if reversed 100,000 miles later.

Starting with simple solutions, a faulty tyre can play stupid games as speed builds, have you two spares for a quick check, or switch front/rear to move the problem around? A tyre can balance fine, but be faulty under load.

If the Torque Tube is the issue, it will be there when stationary at 4000rpm. I do not think it is this. Gearbox, unlikely - if its gone it will whine not vibrate.

Gearbox mount, - reasonable probability this is the cause, the gearbox/torque-tube/engine is carried by this at the rear, and road vibrations are damped out by this mounting.

Wheel bearings do rumble through the shell - I once had to deal with a 535D and it was after the din of that episode that I replaced them[8|]

I have not needed to replace CV's but others think its possible so maybe. Mine have never had any axial wear or float, but I do re-grease them, especially the left one which is heated by the exhaust. I'd suggest doing that one first if you go that route.

As a last resort, slow down[]

good luck
George

 

[ChasR]

If it shakes on acceleration I would put my money on the driveshafts (well, the CVs). Whilst I have had cars with alot of play in the CVs cause bad vibrations, the last time I had a new(ish) CV go bad on me, the play was not all that much (I have had that much play on other cars of the same type with nowhere near the amount of vibrations, yet on that car, a new driveshaft transformed the drive of the car.

 

[TTM]

Thanks for the replies.

The shafts were put back in the same way as they came out. Btw it's difficult to get this wrong, because inner "moons" are different from outer ones.

I'm not sure it shakes any more under acceleration than under deceleration...

One drive shaft being superficially more expensive than 2 separate CV joints, does replacing both CV joints instead of a complete driveshaft make more sense?

 

[eddieedmo]

no the splines wear and the shafts corrode.I have just replaced my driveshafts and trans mount after 177k - the old CV's were not too badly worn but the trans mount was completley shot.Now the back end is quiet smooth and stable throughout the rev range.Can hear the g/box singing away now.

Nick []

 

[edh]

Is the vibration constant? Or does it come & go? I had an intermittent vibration that sounds like you described that we eventually traced to a front wheel bearing! It would start or stop sometimes when steering at motorway speeds. We changed both rear wheel bearings as we were sure the problem couldn't be coming from the front...[]

 

[TTM]

The vibration is constant. It's not hugely obtrusive, and I probably would not feel it if using standard seats instead of bucket seats, and doesn't increase or decrease with speed.
Wheel bearings were all checked and diagnosed fine during the alignment.

I have a spare set of used driveshafts. As they're off a 968 one is too short, but I may take the CV joints and swap the shafts/joints over to the car.

 

[pse_SC]

Whenever I've had roughness from the rear it's always been from CV joint wear, even when other stuff has needed doing too.

Ooh, no, Matron[]

(Sorry not constructive comment, I know)