Definitely- - - -anything that promotes engine lugging- - - -failure to accelerate with increased throttle, is where detonation is most likely to happen. Overdrive is great, as long as it's only used appropriately. A dash-mounted vacuum gauge will educate a driver about when it's appropriate to use a higher gear ratio, and when the engine is getting out of the torque band and performance and gas mileage starts dropping due to too tall gearing.
Jerry
