Know Your 4×4: Transmissions
It’s a matter of preference some prefer manual gearboxes whilst others prefer the feeling of control that an auto box gives off-road. Many auto boxes have a manual mode enabling one to shift gears oneself and some feature a lock done mode to a crawl gear which allows absolute control as the vehicle will not run away from you. Automatic gearboxes tend to have an advantage under conditions where there is a lot of slip (clay and mud) as you can limit wheel spin. Many off-roaders still express a preference for a manual transmission as they feel more in control of the vehicle and the situation they may be in if able to change gears themselves and prefer the ability to brake an engine on descents. A further form of transmission The continuously variable transmission or CVT is available. Fitted to some SUVs with a high range 4×4 option. It transmits torque in a stepless fashion without shift shock. The system employs belts and cones or pulleys to change gear ratios.
Automatic Transmission In a ‘standard’ automatic transmission, a toque converter acts a coupling between the engine and transmission. It takes the place of a clutch and transmits the engine power to the gearbox.
Continuously Variable Transmission (CVT) Is another type of ‘automatic’ transmission. It is fitted to some SUVs with a high range 4×4 option. It transmits torque using steel belts, cones or pulleys to change gear ratios in a step-less fashion.
Manual Transmission A manual transmission uses a clutch between the engine and gearbox to engage or disengage power while changing gears.
The choice between the two transmission types is a matter of personal preference. Some off-roaders prefer manual gearboxes as it gives them a feeling of being in control. Others drivers prefer the freedom that an automatic gearbox gives when driving off-road. Many automatic gearboxes have a ‘manual’ mode enabling you to ‘control’ the changing of gears.
The transfer case is mounted to the gearbox and ‘transfers’ engine power to the front and rear axles equally using two drive shafts. The transfer case is also used to change a 4×4 vehicle from two-wheel drive mode to four-wheel drive mode. A two-speed transfer case would typically transfer power in high ratio: 1:1 gearing or in low ratio: 2:1 gearing (or lower in some cases).
This gear ratio is used on sand, gravel, wet, slippery or icy conditions which require additional vehicle control.
This gear ratio is used in even more difficult conditions which require the maximum control, power and torque at lower speed.
The drive train is the system that transfers engine power to the gearbox through drive shafts to the differentials and the wheels via the drive shafts.