AWD and Bad Noises

[jgiurleo]

Hi everyone,

A couple of weeks ago I noticed a front-end noise like a gear whine but could't tell what it was. It got worse-and was king of making a grinding noise, like something bad was going to go. So I took it to a local Indy Volvo guy and he said he could not pinpoint it and recommended I keep driving. That seemed like a bad idea, but I don't have $$ to go from shop to shop. So I drained and replaced my bevel gear fluid (thanks to instructions on this site.. awesome) and although the noise did not go away, it did change in character. Not quite as much grinding.. definitely still gear whine though. Hmm.

The next thing i did was pull the AWD fuse (#23 in the back). That made a huge difference. It got so much quieter. I can still hear the whine though. The noise is proportional to tire speed. It does not go away in neutral. It is louder on acceleration than coasting. It seems to resonate the loudest at 30-33 mph... and I really can't hear it under 20 mph.

Ideas? Is this just a bevel gear getting ready to die on me? What does the AWD fuse have to do with it?

Thanks for any help - much appreciated.

jgiurleo
2005 XC70 - 155K miles

[howardc64]

Pulling AWD fuse disables Haldex and the car turns into FWD. Rear wheels lost power and so probably less/no load now on parts of the angle gear (AG, aka bevel gear) and the propeller shaft that runs between AG and Haldex.

Probably the next best step is to have a shop run the AWD drive train while on a lift to pin point the noise? This assumes the noise reproduces with much less load while on the lift.

[jgiurleo]

Pulling AWD fuse disables Haldex and the car turns into FWD. Rear wheels lost power and so probably less/no load now on parts of the angle gear (AG, aka bevel gear) and the propeller shaft that runs between AG and Haldex.

Probably the next best step is to have a shop run the AWD drive train while on a lift to pin point the noise? This assumes the noise reproduces with much less load while on the lift.

OK, makes sense. I'll have to take it to a shop to put it up on the lift.

Thanks for the help.

[Hobie]

We have similar noise w/o grinding. Mechanic suggests angle or bevel gear needs replacement. $$$$$$ Trying to figure out whether it is angle gear and if so, if the whole thing needs replacement. Will try your fuse removal diagnostic technique.