I replaced 2 rear subaru tires 6 months/3000 miles ago. I just went to get the oil changed and tires rotated. The manager told me he couldn't do it because I should have had all tires changed at the same time, and not doing it could ruin the transmission. My question is, now what should I do? Get two more new tires or replace all 4? How do I find out if driving with them has already damaged my car? Or is it not a problem, since I've made it this far. Is the place that changed the 2 tires at fault or should I have known this. Thanks for any help!