Noise Identification

[joffa1]

Hi guys,

 

My car is a 2012 FG XR6T Ute TR6060

 

Recently went to new mechanic as clutch slave cylinder failed, when doing the repair he also noticed my tail shaft was stuffed so he installed a new one also. 
 

Ever since I picked it up it now makes this new high pitched noise which I can only describe as like a “steam whistle” sound.
 

It’s not rev dependent but largely speed dependent. It almost always happens when decelerating at around 38-40kmh but also when cruising/accelerating around 60kmh. And it’s definitely louder and more often in the mornings when the car is cold. 
 

I initially thought maybe a problem with the new tail shaft but it if it was out of balance or something I’m sure I would be copping a heap of vibrations. 
 

I’m now leaning more towards a diff issue… but would installing a new tail shaft all of a sudden cause an issue in the old diff?

 

Car is at about 220,000kms now so I would imagine the bushes definitely need doing but any ideas as to what this strange new sound could be and why a new tail shaft has caused it?

 

Keen to hear any advice, liked to be armed with as much info as possible before I return it to the mechanic. 
 

Thanks heaps. 

[k31th]

To summarise; louder and more often when cold, always happens when cruising at 60km/h, is speed dependant, but also doesn't change with revs...

 

That's a weird set of circumstances as when things "heat up" they could start touching when they didn't while cold... and often high pitched whistling would usually be rev dependant... you'd imagine something in the tailshaft/diff/axles area must be at fault if it's speed depedant... but hard to  think of anything that would create a whistling noise... Personally I'd get it run up to ~60km/h on a dyno and hold it steady while somebody checks for sound sources underneath the vehicle.

[joffa1]

Yeah mechanic seemed to think because it was more pronounced with cold conditions it would be diff related? Not sure why that’s the case…

 

Started talking about pinion bearing/harmonic noise due to a different angle or something with the new tail shaft. I don’t know… over my head.