Drivetrain clunk - driveshaft donut?
 

Hi

As my 240 sails effortlessly past 200,000 miles, I have noticed a bit more drivetrain whine and clunk in recent times.

There is a distinct clunk as the drivetrain takes off from stationary, and this remained after replacing all the trailing-arm bushes top and bottom.

There is also a certain whine I've noticed - for instance going down a long downhill road in neutral at about 30-40mph.

Plus there's a rumbly chattering audible as you drive off from stationary, which doesn't seem to change pitch as speed rises, though is eventually inaudible once at cruising speed alongside windnoise and all other sounds.

And - the car is usually parked on an incline with handbrake and in 1st gear. When you start the car, and it goes from being held stationary by handbrake and drivetrain to being held by the brakes, there's always a something of a clunk in the drivetrain as pressure is released by pressing the clutch.

A mechanic with a pit had a look yesterday, and confirmed that all the new bushes are tight as they should be, and that shock mounts aren't rattly. He thought the shocks might be a bit 'weak' but I don't think are making noises.

The one thing he did mention was that in his opinion the rubber donut in the centre of the driveshaft was probably a bit soft. He couldn't confirm if there are sounds coming from this or its bearing while in motion. I don't think there's a burning rubber smell to suggest the bearing was seizing inside the rubber donut. I have no idea whether this piece starting to fail would cause that clunk when moving from stationary.

So the question is: is this rubber donut and its bearing a typical thing to fail around 200k? Or what other things could be candidates for rumbles and slack at this mileage?

Thanks in advance.

John

The doughnut is always deceptively soft and wobbly - I don't think it causes a clunk as you describe. If very worn it could let the bearing spin (but there'd be a rubber smell as you say) and at certain higher speeds I suppose it could let the prop go into an oscilation.
But you can easily test the bearing for whine by undoing the 4 bolts holding the support member and letting the prop drop. Then prise the doughnut off the ball race and you can spin it to listen for wear. If it merely whistles or moans a bit you can lubricate it by prising back the plastic card a fraction and injecting oil inside. I've successfully quietened a whining ball race with a high mileage and it was fine for another 100,000 miles.

The clunk/clack noise when you pull away after releasing the handbrake is the handbrake shoes suddenly freeing. They are floating rather than firmly attached to posts, prone to making noises if dirty or rusty, or breaking up. It would be worth checking inside the drum/disc and greasing the mechanism slightly.

Have you changed the gearbox oil recently/ever? I've found a tendency to whine can often be cured simply by fresh oil. Likewise the rear axle.

Check the prop shaft joints and the sliding bit carefully by pulling/twisting. There should be no movement in the hardy-spicer joints, and minimal at the slider.

I changed the oil on a high mileage 'box which incorrectly had EP90 in it. I bothered to buy a good quality oil - Redline ATF from the US - and it transformed how the gearbox performed. Not sure that this is going to resolve your clunk, but if you are looking to overhaul the driveline, then this is worth doing...

I've just replaced the centre bearing and rubber doughnut - the doughnut is remarkably insubstantial - even a new one! Bear in mind that all it does is to centre the prop which if balanced and with couplings in good condition should need only minimal centering

Good luck with it all