Automatic Transmissions shift between gears automatically to optimize driving, and changes gears based on the driver's throttle pedal, vehicle speed, engine speed, and vehicle load. Typical automatic transmissions have 4-5 forward gear ratios, a Reverse, Park, and Neutral gear. Shifting gears occur automatically once the car is in Drive and there is no need for a clutch pedal or gear shift like there is in a Manual Transmission. There are many components that make up the transmission including the torque converter, planetary gears, sensors & solenoids.
Four-Wheel Drive Transmission
A four-wheel (4x4) drive vehicle has differential gears, both front and rear axles, and a transfer case attached to the transmission. Four-wheel drive vehicles demand maintenance on the transfer case, front differentials, rear differentials, and transmission fluids.
Driving a vehicle with a Manual Transmission requires using the clutch pedal and gear shift to manually shift gears based on the speed of the vehicle. Manual transmissions have been built with anywhere from two to eight gears. Typically, manual transmissions require less maintenance then automatic transmissions however they usually require clutch replacement at some point.