Vibration at motorway speeds

[Gelf VXR]

I’m not doing many miles per year as I work away weeks at a time, anyway last year I noticed a faint drone at motorway overtaking speeds, I suspected a rear wheel bearing might be on the way out, car had some work done over winter, engine came out, back on the road end of Feb, on one journey I noted the drone again a little more pronounced, a few weeks at work, got back, had a trip to London, cruising on the M4 ab the drone is now a vibtration that intensifies when lifting off the gas, slow down the vibration disappears, speed up its back again, drop a gear and heavy vibration, should add that last time out when reversing the diff clunked like I never heard it before. MF changed the half sharfts and the prop centre bearing 5.5k miles back, it was 2013 thou. It’s quite quickly getting worse, any ideas?

Diff and gear box oil service planned, as well as checking for loose missing bolts, will swap front to rear the wheels

[Gelf VXR]

It’s a Monaro 6.0 Vxr, 30.5k miles, new MPSS 4 last summer

[selym]

Prop centre bearing could be shot. Mine was and I got a mega vibration; it was just the prop resonating.
Get it up on the ramps and check it out. I ordered one from Australia and it arrived quickly -
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2...

Bear in mind the prop is in two parts and is balanced; it needs to go back together exactly how it came apart. Find someone who knows what they are doing.

[hammo19]

Same happened to my CV8. Monkfish fixed mine but alas they are not around any more.

[selym]

I had mine done by Topcats near Aylesbury.

[Gelf VXR]

selym said:

Prop centre bearing could be shot. Mine was and I got a mega vibration; it was just the prop resonating.
Get it up on the ramps and check it out. I ordered one from Australia and it arrived quickly -
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2...

Bear in mind the prop is in two parts and is balanced; it needs to go back together exactly how it came apart. Find someone who knows what they are doing.

New bearing ordered just in case, MF did do bearing repair,not sure what that involved, annoying as i have a dyno tune in a couple weeks, may need to cancel

[raving]

Order from Dave @ Walkinshaw

Easy to fit , takes no time

[Gelf VXR]

Gear box and dif oils changed, prop bearing looks ok, dif clunking has gone away, vibration persists, now experincing what sounds like chatter from the gear box area when accelerating at the same time as the as vibration, only in 5th gear thou, could be the gear box output shaft bearing or bent? I think i read somewhere loose 5th & 6th gears that are on the out put shaft can cause vibration

[JAMESHSV1]

Gelf VXR said:

Gear box and dif oils changed, prop bearing looks ok, dif clunking has gone away, vibration persists, now experincing what sounds like chatter from the gear box area when accelerating at the same time as the as vibration, only in 5th gear thou, could be the gear box output shaft bearing or bent? I think i read somewhere loose 5th & 6th gears that are on the out put shaft can cause vibration

Hope you can get it fixed unfortunately for me I ended up having to replace my box

[Aitch H]

JAMESHSV1 said:

Hope you can get it fixed unfortunately for me I ended up having to replace my box

Yeah but you’ve got about a million horse power James, I’m surprised your ‘box lasted as long as it did

[Gelf VXR]

I’m still leaning towards prop shaft balance causing vibration, will change the rubber coupling and new bolts

Edited by Gelf VXR on Monday 28th May 13:17

[SturdyHSV]

Gelf VXR said:

I’m still leaning towards prop shaft balance causing vibration, will change the rubber coupling and new bolts

Edited by Gelf VXR on Monday 28th May 13:17

That wouldn't be gear dependent though, it'd be speed dependent, prop would rotate at the same rate regardless of the gear...?

[selym]

SturdyHSV said:

That wouldn't be gear dependent though, it'd be speed dependent, prop would rotate at the same rate regardless of the gear...?

I agree in theory, but in practise and having had a shot centre bearing it doesn't vibrate until it does - then it resonates and doesn't stop until you slow down to a stop.

[SturdyHSV]

I used my shot centre bearing as an excuse to get a carbon fibre prop

Never noticed any vibration or resonance though, but obviously depends how shot it is!

[Gelf VXR]

It is speed dependent, vibration is around 80~90, worse when not loaded, the chatter is in fifth on load. Could be a bent coupler bolt, or the coupler itself , I just learned the coupler can be put on the wrong way round also.

From Aussie forum
A warning for those who replace the rubber coupling in the future.

Today, as I was just about to throw the old coupling (donut) into the bin, I noticed 6 markings on the outside of the donut, they were like arrows, 3 facing one way and three the other way, they were lined up with the bolt holeys. So I checked my service CD ( which I should have done beforehand) and the 3 facing forward should line up with the yoke on the tail shaft and the three facing back connect to the diff. It doesn't matter which way you put the coupling on as long as the forward facing arrows line up with the yoke on the tail shaft. This may be a bit hard to understand at the moment but if you need to replace the coupling you will understand what I mean.
So I checked the one I had installed and with a 50/50 chance of getting it right I naturally had it the wrong way, so I had to remove all the bolts and rotate the donut by one bolt hole.
I hope this lesson helps people in the future.

[selym]

SturdyHSV said:

I used my shot centre bearing as an excuse to get a carbon fibre prop

Never noticed any vibration or resonance though, but obviously depends how shot it is!

Oh, mine was SHOT!

[mfp4073]

[quote=Gelf VXR]It is speed dependent, vibration is around 80~90, worse when not loaded, the chatter is in fifth on load. Could be a bent coupler bolt, or the coupler itself , I just learned the coupler can be put on the wrong way round also.

From Aussie forum
A warning for those who replace the rubber coupling in the future.

Today, as I was just about to throw the old coupling (donut) into the bin, I noticed 6 markings on the outside of the donut, they were like arrows, 3 facing one way and three the other way, they were lined up with the bolt holeys. So I checked my service CD ( which I should have done beforehand) and the 3 facing forward should line up with the yoke on the tail shaft and the three facing back connect to the diff. It doesn't matter which way you put the coupling on as long as the forward facing arrows line up with the yoke on the tail shaft. This may be a bit hard to understand at the moment but if you need to replace the coupling you will understand what I mean.
So I checked the one I had installed and with a 50/50 chance of getting it right I naturally had it the wrong way, so I had to remove all the bolts and rotate the donut by one bolt hole.
I hope this lesson helps people in the future.
[/quote


That was a difficult one to spot, I'll put that on my list, thanks for the update.

John

[monkfish1]

Gelf VXR said:

It is speed dependent, vibration is around 80~90, worse when not loaded, the chatter is in fifth on load. Could be a bent coupler bolt, or the coupler itself , I just learned the coupler can be put on the wrong way round also.

From Aussie forum
A warning for those who replace the rubber coupling in the future.

Today, as I was just about to throw the old coupling (donut) into the bin, I noticed 6 markings on the outside of the donut, they were like arrows, 3 facing one way and three the other way, they were lined up with the bolt holeys. So I checked my service CD ( which I should have done beforehand) and the 3 facing forward should line up with the yoke on the tail shaft and the three facing back connect to the diff. It doesn't matter which way you put the coupling on as long as the forward facing arrows line up with the yoke on the tail shaft. This may be a bit hard to understand at the moment but if you need to replace the coupling you will understand what I mean.
So I checked the one I had installed and with a 50/50 chance of getting it right I naturally had it the wrong way, so I had to remove all the bolts and rotate the donut by one bolt hole.
I hope this lesson helps people in the future.

Almost certainly the 5th gear slack on the mainshaft. Fairly common issue, but new mainshaft and 5th gear required.

[Gelf VXR]

Got new rubber couplings and a center bearing ready to be fitted in next month, im hoping its not the gear box, i checked repeatedly, the vibration is at 80~85 in 4,5 and 6th gear and with clutch in.