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VX V6 Auto. Strange "moaning" noise from driveline.

mirrabucca

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VX V6 auto. Noise started about 500 k's ago. Started as a moaning nolise coming from under the car at about 40 kph when starting from cold. Noise disappeared after abour 5 k's. I did a 300 k's trip and no problem or noise. Then over the days, it got worse. Lasting about 10 to 15 k's into my journey, but only from a cold start.
Now it comes in at about 40 k's, disappears as I speed up, then comes in at 50, goes away at 60. Back to about 70, and quiet at 80. But still only from a cold start.
When the noise is apparent, it doesn't change if I coast, decelerate or slip into neutral. I had a passenger in and they said it sounds like its coming from the rear left hand side. But as I drive it seems to be coming from nearer the middle. Hard to tell.

I jacked the car up and put it on stands under the body. Spinning the wheels by hand there's no noise. Start the car (making sure I set TRACTION to OFF!) no noise at idle, either in gear or in neutral. Revving it up to 40 k's and the noise is there, same at 70. Same as on the road.
If I block either rear wheel, the noise is still there at the same speeds. But I still cant tell where it's coming from.
If it was wheel bearings, blocking that wheel would stop the noise. I dont suspect diff wear as the noise is constant, accelerating, decelerating and coasting.

I had the tailshaft centre bearing replaced about 15000 k's ago. Maybe a dud bearing? Or diff pinion bearing? Or Gearbox output shaft bearing?
Maybe up on a hoist would make it easy to sort out where the noise is coming from.
Yes, I am taking it to a transmission specialist, but I thought I'd see if anyone had a similar experience.
 

vxcalais_01

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I was told to replace my tailshaft bearing 50,000kms ago and never bothered. Have you checked if it is the engine mounts ? Some of the VX's like mine have variable steering where the column drops at certain speeds so the column could be faulty or hitting on something. Flush out all the powersteering fluid (suck the oil out of the reservoir) and put some new fluid with a stop leak in it like Rislone, or Lucas and see if it goes away after a few 100kms.
 

losh1971

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Do you have an LSD?
 

Fu Manchu

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I’m going to suggest something completely different.
What if one of the accessory pulleys Is off and the outer edge of the belt is catching. When the belt warms it stops moaning. Have had this twice on cars.
Check the drive belt and inspect for signs of wear on the sides.
 

mirrabucca

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Thanks for the replies and ideas guys.

1. It happens at about 40 k's, then stops between 40 and 50. Back just under 60 k's but gone at 60.
Comes in again around 90. Gone above that. Doesn't matter what gear I am in. Sound is a constant frequency, ie it doesn't rise as speed rises.
So unlikely engine based.

2. No, Not LSD. I dont do drugs... Sorry, standard diff. I can jack the car up with one wheel off the ground and after diabling traction control, and running the car (one wheel only turning) the noise comes in at the same speeds as on the road. It happens when either wheel is off the ground. (so not wheel bearings).

And I took it to my transmission specialist. He drove the car, but as I had driven to his workplace, the noise was only happening at about 90 K's and very intermittent.
He said that it didn't sound like any "usual" noise, ie bearings, brakes etc. But because it hasn't got worse over the last month it probably wasn't serious. He also said "It'll be something stupid" He also sugessted I spray some CRC around the centre bearing dust seal it case it's dry and squeaking. Done. The noise was still apparent after I treated it, but today it's barely there.
Time will tell.
 
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