Mismatched tires on car
What will mismatched tire sizes do to a minivan? I had tires professionally installed and later rotated and balanced. On my last visit to have them rotated and balanced, they told me that the 2 front tires had too much wear to rotate/balance. We replaced all 4 tires and upon inspection noticed that one of the front tires was a 60R instead of a 65R like the other 3. They were the same brand but one was a different size.
After they were rotated and balanced the first time (little tire moved to front-no one noticed at that point either), transmission had to be replaced within a 2 year window of time.
What are your knowledgeable thoughts on this situation?
You didn't mention whether you bought this van new or used, but this may explain how you might have had one mis-matched tire in the first place.
Normally we never recommend that you mix tire sizes on the same axle and possible mechanical damage is one of the reasons.
Vehicles which are 4 wheel drive usually carry a stern warning in their users manual to never mix tire sizes because of damage which can be done to the drive train. 2x4 vehicles may be somewhat more forgiving but the same principle applies because the resistance which different sized tires present to the power train are different and this can be translated into mechanical stress.
For temporary use, such as a flat tire then driving to the nearest repair facility the problem may not be enough to be noticed, so there wouldn't be an issue if you had a spare tire which was a different size, but too often a spare tire gets put into use and then gets forgotten about so the best practice is to have all tires, including the spare, the same size.