Rumbling/grinding noise around 30km

[mboy]

Hi all,

I have a VX Clubsport R8 (Auto). At around 30km it makes a rumbling grinding noise. I first thought it was a wheel bearing so had that changed to no avail. It seems to start arouns the 20-25km range and is pretty much gone around 50km.

I'm at a loss - can anyone suggest what to check next? If it were brakes wouldn't it be constant?

Shane

 

[Turtl3]

U need to establish whether it is road speed related, engine rpm related, or gearbox related. Try doing the same speed its happening at with different gears engaged. Might pay to get under the car and check the tailshaft bearings, and for freeplay in the output shaft of the gearbox, input shaft on the diff, and while ur there check the cvs for play aswel. If the rear wheels r off the ground rotate them and see if there is any unusual resistance. Could be one of the other wheels bearings that wasnt changed. Do a gentle swerve and brake test to see if the noise worsens with weight shifted around the axis of the car to rule out bushes/suspension

 

[billythakid]

Strut mounts are you're likely suspect
if they have never been changed they will be worn and rumble

 

[Freedon]

or possiblly a draging handbrake shoe.

 

[mboy]

Hey guys,

I have put it into neutral whilst at 30km which didn't seem to change the noise.
I haven't managed to get under the car yet but I have tried applying the handbrake whilst its happening which didn't change or affect the noise.

I had a friend sit in the car with me and they said that they would describe it more like a rubbing noise rather than grinding. With this I would now describe it as a rubbing noise that progressively turns into a low rubbing/rumbling noise. At it's worse it seems to start just before 25km and has disappeared by 45-50km. At it's best it's either non audible, or is mainly present at 30km.

First thing in the morning or first drive of the day it doesn't seem to be there (or at least it's way less) but if I have to do a lot of driving at around 30km it seems to progressively get worse.

I will be installing a new diff next week so will have a good look under the car.

 

[Dirbatua]

Could be the exhaust rubbing against the underside of the car if its not a stock system or if your engine mounts are worn.

 

[sidecar55]

Have a look at your tyres, they can sometimes give you a noise like a worn bearing. Look for variations in the height of the tread blocks.

 

[vc commodore]

Have a look at your tyres, they can sometimes give you a noise like a worn bearing. Look for variations in the height of the tread blocks.

Doubt it would be this....With tyres, the noise gets worse with road speed, rather than disappear

 

[Turtl3]

is there any particular reason your changing the diff? ... could be your culprit right there if someone has told u its on its way out...while your under there check your tailshaft and gearbox shaft for play. give the cvs and wheel bearing a good going over aswel. are all your wheel nuts tight?

 

[mboy]

is there any particular reason your changing the diff? ... could be your culprit right there if someone has told u its on its way out...while your under there check your tailshaft and gearbox shaft for play. give the cvs and wheel bearing a good going over aswel. are all your wheel nuts tight?

Thanks. The diff is single spinning. It's the third second hand unit I've had since the noise started so do not think it's that (This is another story).

Had the alignment done after I changed the the strut mounts and whilst it was on the hoist we had a good look at the drive shaft and cvs etc to see if there was any play or abnormalities. The mechanic said everything looks fine. However there is a front tyre worn funny on the inside that they say could be the problem but I'm still not convinced, mainly due to the amount of noise it makes. I will keep checking though, and will put the fronts on the back to see if this changes anything.