Tires: tire diameter, tire diameter, awd

Question
I bought new tires for the front of my car because they seemed to be going bald.  They are the same size as the tires that are on my car but the mechanic told me that my car's (Honda crv 1999) transmission might bind up due to the fact that the back tires are a different diameter.  This problem was caused because the back tires are worn.  Should i get two more tires or can i wait?

Answer
Jamie,

Honda has the answer.  It is their transmission and they will be able to tell you how tolerant it is of differences in diameter.  

But from what I know, it is a bad idea to mount only 2 tires on an AWD and on some vehicles, it only takes a few miles to cause damage.