tjw7676
02-16-2009, 08:45 AM
I need some help diagnosing a problem with 01 xc70 with 178,000 on it. The car makes a hum/whine sound on acceleration from 25 to 65mph and the same hum/whine sound on deceleration. Once car is set on cruise the sound dies down until I have to give it some gas. It is coming from the rear of the car. I am thinking either a bad driveshaft bearing (pinion bearing I believe) or a bad wheel bearing. I have checked that the awd by putting car on jacks and in neutral then moving front wheel to check that the rear moved; and both sides work. What does a bad pinion bearing to Viscous Coupler look like and does it exhibit these same symptoms? I could not find this same exact symptom, thanks!