What are the types of four-wheel drive chassis?

[Danielle]

On-demand drive: Under normal road conditions, the vehicle generally adopts rear-wheel drive. Once encountering poor road conditions or wheel slippage, the computer automatically detects and immediately distributes the engine's output torque to the two front wheels, naturally switching to four-wheel drive mode. Its greatest advantage is simple operation, but at the same time, due to computer control, the vehicle's response may be slower. Part-time four-wheel drive is suitable for high-end RVs and urban sports cars. Full-time four-wheel drive: In this drivetrain, the front and rear wheels always maintain four-wheel drive mode. While driving, the engine's output torque is evenly distributed between the front and rear wheels, ensuring equal torque on both axles. The full-time drive system offers excellent driving control and tracking performance. However, this system consumes more fuel and has poor fuel economy. Full-time four-wheel drive is suitable for professional off-road vehicles. Part-time four-wheel drive: This is a four-wheel drive system where the driver can manually choose between two-wheel drive and four-wheel drive. The driver can switch between two-wheel drive and four-wheel drive modes by engaging or disengaging the transfer case based on road conditions, making it the most common drive mode. Its most notable advantage is the ability to select the drive mode according to actual conditions, making it more economical. Part-time four-wheel drive is suitable for SUVs and non-professional off-road vehicles.

[Rodney]

I've done quite a bit of research on 4WD chassis. The body-on-frame chassis is the most classic type, featuring an independent ladder frame that old-school off-road vehicles love. It offers excellent torsional resistance, preventing body deformation on bumpy roads. Part-time 4WD chassis pairs best with this setup—manually switching between 2WD and 4WD modes, engaging 4WD for exceptional stability on rough terrain. Full-time 4WD chassis follows a different approach, with all four wheels constantly delivering power, ensuring no slippage during high-speed cornering—Audi's quattro system exemplifies this type. On-demand 4WD chassis are gaining popularity now, offering fuel efficiency and agility for city driving. They primarily use front-wheel drive, activating the rear wheels only when slippage is detected—commonly seen in urban SUVs like the CR-V. The Super Select 4WD chassis serves as a compromise, functioning like full-time 4WD for all-weather capability while also allowing pure rear-wheel drive for fuel savings—the Pajero relies on this system for global adventures. Unibody chassis dominate the market today, with integrated designs significantly reducing weight. When paired with electronic differential locks, they prove highly reliable on slippery surfaces.

[OAddyson]

My SUV has a unibody chassis with an on-demand four-wheel drive system, which is quite worry-free for daily use. The chassis rigidity is sufficient, and it doesn't make clunking noises when going over speed bumps. In city driving, it mainly operates in front-wheel drive mode. Once when the overpass was icy, the system immediately engaged four-wheel drive to stabilize the vehicle. Friends with part-time 4WD chassis often complain about the cumbersome operation, having to stop to switch modes, unlike our automatic switching which is more convenient. Full-time 4WD chassis do consume more fuel, but the traction in rain and snow is truly stable, especially practical in northern regions. Off-road enthusiasts all opt for body-on-frame chassis with three differential locks - the high ground clearance prevents chassis scraping when traversing artillery shell craters. For urban commuting, unibody chassis are perfectly adequate, offering lighter weight for quicker acceleration and easier parking in multi-story garages.

[McMakayla]

The four-wheel drive system cannot function without proper chassis coordination. A body-on-frame chassis with a sturdy ladder frame can handle heavy loads; a full-time four-wheel drive system paired with independent suspension offers flexible handling; a part-time four-wheel drive chassis saves space and fuel; and a selectable four-wheel drive chassis requires a low-range gear for sufficient power. Remember, the chassis skid plate is crucial to prevent gravel from damaging the driveshaft.