[STRMTRPR]

Past few weeks I've been getting this weird ambulance hum sound. 2 mechanics didn't really know what it was so I had to bring It in to the BMW dealership to get it checked up. The sound is supposedly caused by the Transfer case with bushing. Price to fix it is very high at the dealership . I was wondering where they would sell them and how much would it roughly cost to do it at a indie mechanic or if it's possible to DIY.