Vehicle speed (mph), engine speed (rpm), tire diameter (inches), trans gear ratio, and rear axle gear ratio are all interrelated. If you know four out of five of these values, you can determine what ...

Power, power, we all want more power. Naturally, most people think of the engine when upgrading their 4x4, since that’s where the power comes from. Is your rig a slug in the rocks or on the road? Just ...

Why is the Gear Vendors overdrive so popular on HOT ROD Drag Week? Racers know it will live behind 4,000 hp, can be installed in a weekend, and doesn't share fluid with your transmission so it won't ...

Even good cars only give the driver two speeds to monitor: engine speed and vehicle speed. And while it’s the engine that ultimately does the work to turn the wheels and move a vehicle, a lot goes on ...