Volvo: 99 CX70 viscous couple or angle problem, viscous coupling, awd cars

Question
I've been experiencing a jerking when I make tight turns at slow speeds.  My mechanic has diagnosed this as a problem with the viscous coupling system and I replaced it with a used viscous coupling system, but the problem still persists.  I'm having the parts guys send out another one and we're going to try that, but he also mentioned that my mechanic may have misdiagnosed the problem and it could be something wrong with the angle gear.  The sound is coming from the rear of the car.  I was wondering if you had any more insight into this problem.  Thanks.

Answer
Megan,
I would say since the noise is at the rear of the car then the viscous would be at fault. I will say that there have been many problems with noise, jerking with the AWD cars. Many angle gears have also gone bad. Now sometimes I have seen that the noise in a drive line travels through the drive shaft and makes you hear the noise in some other area. Is it possible to get a second opinion?