Car lingo? Need Help understanding!!?

Dana is a brand. They manufacture differentials and the like. Differentials are what connects the axels on rear wheel drive cars/trucks. They are connected to your transmission through a drive shaft. Dana is a brand. It has been used in some Ford trucks. D35 is just a model. 3.73 is a gear ratio. As in 3.73:1 For every 1 revolution that is made in one of the shafts in the transmission, the shaft that turns the drive shaft will turn 3.73 times. Your lower gears will be like this. The higher the number, the more the wheels will spin. Your last gear, e.g. the 5th gear in a 5 speed transmission, will always be 1:1 ratio.