2004 xc70 awd intermittent howling

tara_tabler · Post by **tara_tabler** » 01 Apr 2017, 12:46

My car runs and drives perfectly. A few weeks ago, it started howling (like a bearing howl) and it sounded like the driver front. We brought it in the shop to check and it just stopped howling. No change in driveability at all, no vibration, trans still shifts perfectly. After approximately 800 miles, the howling started again but sounded like it was on the passenger front this time. Wheel bearings also checked out fine. We pinpointed the sound to strongest at the trans and bevel gear but cannot narrow it down further. No fluid leaks, no metal in fluid for either the trans or bevel gear. Vibration at higher speeds but only when the howling is present. Any thoughts? We're stumped by a howling with no metal contamination that goes away.

Post by **abscate** » 03 Apr 2017, 07:09

Its really hard to check wheel bearings on these cars so I would not rule those out. IF the howl came suddenly, though, it probably is not wheel bearings. Its also more of a whhhrrrrrrrr or gggrrrrrrrrr.

I think the bevel gear diagnosis sounds most likely, Tough one.

Post by **shiloh51933** » 04 Apr 2017, 10:42

tara_tabler wrote: ↑01 Apr 2017, 12:46 My car runs and drives perfectly. A few weeks ago, it started howling (like a bearing howl) and it sounded like the driver front. We brought it in the shop to check and it just stopped howling. No change in driveability at all, no vibration, trans still shifts perfectly. After approximately 800 miles, the howling started again but sounded like it was on the passenger front this time. Wheel bearings also checked out fine. We pinpointed the sound to strongest at the trans and bevel gear but cannot narrow it down further. No fluid leaks, no metal in fluid for either the trans or bevel gear. Vibration at higher speeds but only when the howling is present. Any thoughts? We're stumped by a howling with no metal contamination that goes away.

Sounds like bevel gear would make more sense, the howling sound changed sides to your ear because it's really in the center of your car. Has the bevel gear ever been serviced(meaning oil change)? People tend to forget about the bevel gear, differentials and rear end services. The bevel gear could cause vibration, the pinion gear has a bearing near the companion flange for the prop shaft that can go bad.

1998v70xcbill · Post by **1998v70xcbill** » 04 Apr 2017, 21:09

Oil cooler thermostat makes noise when cold. Goes away when oil warms up. I don't let it bother me anymore.

Post by **abscate** » 05 Apr 2017, 04:11

1998v70xcbill wrote: ↑04 Apr 2017, 21:09 Oil cooler thermostat makes noise when cold. Goes away when oil warms up. I don't let it bother me anymore.

I don't think this happens on P2s, the oil thermostat moved into the biscuit oil cooler in 1999

tara_tabler · Post by **tara_tabler** » 18 Oct 2018, 14:52

It ended up being the hub assembly. Supposedly it howled when part of the race came loose until the bearing chewed it all the way up, was my understanding. Either way, replacing the hub stopped the howl. Thanks for the replies!

Post by **shiloh51933** » 20 Oct 2018, 08:44

I know you stated that issue was resolved but since the "bevel gear" was mentioned, now might be a good time to service that bevel gear with some new oil. Good way to avoid that from howling, much cheaper also. Another overlooked item would be the rear differential and ATF service.