I have a '98 Passport that can be shifted into 4WD. I have to replace one tire (nail in sidewall) and have been told I need to buy all new tires. I understand that this is true due so I will not potentially overhead (ruin) the differential. However, if I do not engage the 4wd, can I continue to use mismatched (tread and/or brand) tires for a year and then buy a set? I do not wan to ruin the differential but I hate spending $500 because I ran over a nail and ruined one tire.