It has happened for sure. I remember one X5 in particular. He was running aftermarket winter tires. Exact same size and load rating as stock. Don’t remember the brand. Every spring, we had to replace the transfer case. On the third one, BMW said they would not warranty it again unless he was running star spec tires. So he bit the bullet and purchased a winter rim/tire package from us. His transfer case never failed again. There is a service bulletin for diag on them. The first thing to check is if the vehicle has star spec tires and they are all within 3mm of tread depth to each other. If not, we are supposed to deny the claim.What? My X5 ran OE Bridgestone's, than aftermarket snow Bridgestone's in winter, than OE Bridgestone's, than aftermarket snow bridgestone's, than aftermarket Michelin's, than aftermarket snow Michelins, and transfer case never had a hick up.
Can you imagine, on 328i I put 205/55 R16 instead of 225/45 R17 for winter, with aftermarket Continental's and nothing happened.
So tell me please how many transfer case warranties BMW refused for buying tires elsewhere? They cannot, period!
Or better yet, why would let's say Michelin Pilot PS4S destroy my transfer case on 328 xDrive but Bridgestone DriveGuard won't?
Every spring we replace dozens of transfer cases. Most techs do so many we can usually replace one in only 45 mins or so.
You have been lucky. The older E90 seem to be less picky about tire size. I run an aftermarket square set of tires on my own E90 in the winter.