Rear Diff Noise

[skn]

I have a 2005 XC90 2.4D 163 which I have owned from new. It has now done 100k miles and recently started to make a droning sound around 40mph which is wheel speed related. I assumed it was wheel bearings so first changed the rears then the fronts. This made no difference. Next I ran the car with all four wheels off the ground and established that firstly the AWD drive is working well and secondly the rear diff is noisy. I diagnosed this by using a snooker cue as a stethoscope:-)

I can't see any sign of leakage so expect to find some fluid in there. I have ordered some redline GL5 75-90W so will try this first before either stripping or replacing the diff.

Has anyone else had this problem and does a fluid change help?

Thanks in advance for any help, Simon

[Rooster]

It is unusual to see a diff fail on an AWD car,

I've only ever seen a couple, one on a XC90 and one on an XC60 but they were on newer cars than yours,

[Ducklakeview]

Surely the diff will be silent, unless it is under load and being driven?

Mike

[skn]

Thanks for replies. The diff is definitely not silent whilst running at 40mph off the ground:-) I suspect the noise is a worn pinion gear so thats meshing/ rotating whether under load or not.

My plan of action is to change the oil and then retest. If that doesn't work will remove diff and strip it and check for wear. As Volvo doesn't sell any internal parts for the diff I will have to try and source a good 2nd hand one to use for either donor parts or complete swap.

Just got a price from Volvo for new diff £2.4k!

[Ducklakeview]

Originally Posted by skn

Thanks for replies. The diff is definitely not silent whilst running at 40mph off the ground:-) I suspect the noise is a worn pinion gear so thats meshing/ rotating whether under load or not.

My plan of action is to change the oil and then retest. If that doesn't work will remove diff and strip it and check for wear. As Volvo doesn't sell any internal parts for the diff I will have to try and source a good 2nd hand one to use for either donor parts or complete swap.

Just got a price from Volvo for new diff £2.4k!

I take it you've had the car on a two post lift with all 4 wheels running free? Otherwise the rotating input into the diff stops at the haldex coupling.

Mike

[Clan]

Originally Posted by skn

Thanks for replies. The diff is definitely not silent whilst running at 40mph off the ground:-) I suspect the noise is a worn pinion gear so thats meshing/ rotating whether under load or not.

My plan of action is to change the oil and then retest. If that doesn't work will remove diff and strip it and check for wear. As Volvo doesn't sell any internal parts for the diff I will have to try and source a good 2nd hand one to use for either donor parts or complete swap.

Just got a price from Volvo for new diff £2.4k!

YOu will probably find just one of the differential carrier bearings is rough , worth trying to find a new bearing .. one of them is fairly easy to come by but if i remember right the other isnt marked so you may have to search around .. the bearing pre-load and pinion mesh have to be checked and adjusted after though ,

[skn]

Originally Posted by Ducklakeview

I take it you've had the car on a two post lift with all 4 wheels running free? Otherwise the rotating input into the diff stops at the haldex coupling.

Mike

Hi Mike,

Yes all four wheels off ground, running at 40mph:-)

[skn]

Originally Posted by Clan

YOu will probably find just one of the differential carrier bearings is rough , worth trying to find a new bearing .. one of them is fairly easy to come by but if i remember right the other isnt marked so you may have to search around .. the bearing pre-load and pinion mesh have to be checked and adjusted after though ,

Thanks Clan, will give it a go and report back.

[skn]

Clan,

Don't suppose you have any spec for the bearing pre-load, backlash etc please?

[Clan]

Originally Posted by skn

Clan,

Don't suppose you have any spec for the bearing pre-load, backlash etc please?

volvo don't publish any figures but it should comply with any standard final drive kind of figures i would think .