Tire Issue? Or not?

[ImolaRedM3]

I Bought a 03 X5 4.4l in September. In December the Tranny let go. After a two month ordeal over getting the tranny rebuilt. She is back and driving great. Although it does need tires. So after shopping online I noticed that my particular x5(with sport package and 19's) should be running 255/50R19's on the front and 285/45R19's on the rear because of staggered rims. So I then went outside to check what the vehicle has on it now because I never really paid much attention. I found that someone has put 255/50R19's all the way around. Stretching them over the wider rear wheels.

My questions is this. Could that have been what caused the tranny problem to begin with? Will it hurt me to continue driving the x5 until I get new tires? Or should I park it? Any input is appreciated. Thanks