For many years, the front suspensions on 4WD vehicles were nearly identical to the rear suspensions. A large live axle supported with either leaf or coil springs for support was standard for most 4WD trucks, an example of which is shown in Figure 6-42. While strong, these systems did not have outstanding ride quality. To improve the ride and handling of 4WD trucks, manufacturers began to redesign the front suspensions to allow for independent wheel movement. One novel approach to this was Ford’s Twin-Traction Beam or TTB. This system uses a live front axle that contains U-jointed axle shafts that allow for independent wheel movement for improved ride and handling while still retaining the durability and strength of traditional 4WD. Manufacturers of 4WD vehicles today often mount the front differential directly to the chassis. Short FWD drive shafts then connect the differential to the wheels.
An example of this arrangement is shown in Figure 6-43. This allows fully independent suspension movement. Full live front axles can still be found on heavy-duty light trucks, but the majority of trucks now have independent front suspensions whether they are 2WD or 4WD.
