CRV 2005 noise from Rear and feels sluggish



I have a CRV 2005 Realtime AWD with 70k miles. Recently I am hearing a whining noise from Rear.Probably started about the same time as new tires (3 weeks ago). A friend of mine has an 2004 CRV. He said that it feels sluggish … might be the AWD is on all the time… RPM’s look fine while driving. No gear change issues or other noices…

Got the Rear diff fluid (with honda fluid) changed last week. No change. Got an appt with dealer in 2 weeks… they are booked!!!

Any ideas on what it could be… This does not seem like tire noise…