Correct me if I'm wrong but ...

If you HAVE to purchase only 2 new tires, they should go on the rear since the 'smaller diameter' old tires will be read as turning faster by the speed sensor. This will mean that the TOD will not be trying to engage to compensate for rear wheel spin.

That said, I don't advocate replacing only 2 tires. My front are also worn due to lack of rotation. I'll be replacing all 4 soon (anyone want 3 decent 33x12.50 Wranglers???)

Tom