2009 CV - Intermittent weird groan noise/vibration in rear upon acceleration

[hophead]

Hi There

We recently purchased a 2009 RAV4 CV Auto with 80,000km on it (private sale). We took it for a considerable test drive, but after the first 100km or so after getting it home, it has started making an occasional vibration/groan noise in the rear upon initial acceleration. It only lasts about 1 second and seems to be accentuated when turning and accelerating at the same time, but sometimes just going straight. I was able to replicate it more consistently with the 4x4 lock enabled and moving forward (no turning), but still not 100% of the time. Seems to do it more frequent after leaving it overnight.

Doing some reading around I'm a little worried it is the rear diff coupler, which seems to have a known issue where a Toyota TSB with 9 year/unlimited KM warranty for repair has been issued in Canada, but no where else. Only difference is people report this similar noise at high speed too, where ours is only ever upon initial power and cruises fine.

Any ideas what it might be or further things I could do to diagnose the issue?

Thanks for any help.

Edited January 13, 2015 by hophead