My truck and overdrive?

I agree with Rick. This on changes your basic gear ratio. From 1:1 (off) to 2:1 (on). If you have this function on in city driving. The transmission will constantly have to be shifting up and down. Causing excessive wear on the gears and create heat. Which in turn puts more stress on the . Use this function of having your overdrive -ON- only on the highway 65 mph or higher. This is a gas saving feature for highway speeds only. It does not good in city driving.