Gearbox chatter and whine from back

[Anto_Holmes]

Since having the underbody redone over the winter, a whine has come into it from what seems to be the back. Chatter has also come into the gearbox from 3rd to 6th gear on deceleration with what sometimes sounds like a woo woo nice from the propshaft area. The whine appears from 60kmh upwards. One suggestion on the whine was handbrake shoes but that doesnt seem to be it. Wheel bearings are tight also, no issue there.

What ive done so far to try diagnose is drain the back diff which I found was almost dry. Adding new oil didn't solve it. I was getting worried that the gearbox was an issue because of the chatter I was hearing as it was getting worse.

I was with the mechanic today and we drained the box oil. Aside from the oil being well driven, there is no sign of anything wear wise on the magnet or in the oil. The oil is clean from any shine or metal pieces and the magnet only had its normal minimal fur. He reckons the box is OK given the 6 speed is very strong.

None of this was there before the underbody aside from slight chatter in 3rd. He's going to remove the prop shaft again to ensure all joints are loose and im going to replace the centre bushing.

Apologies for the essay, but im basically just wondering, what else could be causing the issue?

 

[Ciaran WRX]

Loose Heat sheilds can do that but easy to spot so I'm sure that's not that..did you swap out any sections of exhaust sometimes can be hitting or close to body causing noises ect again easy check once on ramp.

 

[Anto_Holmes]

Ill get him to check hear shields as well. Back box was changed but whine was there beforehand. Like a needle in a haystack.

 

[Ciaran WRX]

Exhaust hanger rubber thingys to can split get loose or pop off cause noise

 

[mack]

is your exhaust midpipe touching of the propshaft bearing carrier behind the gearbox ?

 

[Outaline]

Does the whine go away when you decelerate ?

 

[Anto_Holmes]

Does the whine go away when you decelerate ?

No it stays there, just the pitch rises with speed and lowers with slowing down but gear chatter happens on decel.

 

[Anto_Holmes]

is your exhaust midpipe touching of the propshaft bearing carrier behind the gearbox ?

Ill check that out as well

 

[BazGF8]

If the rear diff was dry it could be the bearing on the diff itself or the pinion bearing

 

[Anto_Holmes]

If the rear diff was dry it could be the bearing on the diff itself or the pinion bearing

It was dry, for an awful long time I reckon. Put fresh oil in and is being done again now but there wasnt much fluff on the magnet when I did it. Noise only there though since the underneath was reassembled after refurb of body

 

[Outaline]

No it stays there, just the pitch rises with speed and lowers with slowing down but gear chatter happens on decel.

A whine usually indicates a diff issue with crown wheel / pinion won’t be a big deal though .

 

[Anto_Holmes]

A whine usually indicates a diff issue with crown wheel / pinion won’t be a big deal though .

Im thinking a bit along those lines as it was dry for an unknown length of time. Only thing bugging me is it wasnt there before the underbody job and clutch change but is there since.

 

[Eoinmack]

Has to be something put back wrongly then if it wasn't there before that,,, or clutch fault. Too technical for me but logic would say take it down and check again lol

 

[BazGF8]

Put it on a ramp and drive it on the ramp and get the mechanic to use a long screw driver up to his ear and push it against the rear diff to diagnose it ,

 

[Anto_Holmes]

Thanks for the help, plenty to try and localise it.