Can your replace tire size 245 70 17 t with 235 65 17?

Can you? Yes you can. Should you? No, you should not because the 65 series tire is 4.84% (1.47") smaller in overall diameter than the 70 series tire. You should never go over or under 3% difference. If you wish to go to a 65 series tire then you need to install 265/65-17 tires that are only 0.19% (.06") larger. That size will be an Excellent fit. A 255/65-17 will also work well but not quite as well as a 265/65-17. A 235/65-17 will not work well and you should not install that size. Know that the 265 may rub the fender liner when you turn sharply so check that.