1997 4runner vibration and buzzing noise fix 

0 to 5mph i could hear a low volume tap in the middle area by transfer case as the shaft was starting to turn
5 to 50s mph nothing
60 to 70mph buzzing noise rear and vibration in the rear window
i remove tires to check for wheel bearings and nothing wrong
replace to rear tires thinking of bubble tires separated or out of balance and nothing
finally got a propeller shaf and replaced it
as i was there i check for transfer case bearing n realized that the nut was loose
n got it tight
and tha my friend took care of the problem
best regards