Noisy AWD
 

I just purchased a 98 Honda CRV had 70,000 miles on it 1 owner car. I noticed when it rains I get a noise from rear when all wheel drive engages. So I Google seems like a common problem was told just needed to change differential fluid easy. I changed fluid using a CVT fluid but not Honda's rained 2 days later so I spun the tires noise didn't go away. Now lady owned before me put 195/70 tires on instead of 205/70 but all 4 are the same I wouldn't think that's the cause. Do I just need to buy Honda's fluid?