DESCRIPTION
Note. This article applies to all vacuum operated front axles in Dakota(1987-92), Ramcharger (1985-93), and Ram Pickup from 1985-2001. This article also applies to 2002 Ram Pickup 2500-3500, however does not apply to Ram Pickup 1500. The front axle for Ram Pickup 1500 is not vacuum operated. For information and diagnosis for front axle on 2002 Ram Pickup 1500, see appropriate DIFFERENTIALS/DRIVE AXLES article.
The Locking Hub - Vacuum Control System can be shifted between 2WD and 4WD high range, from inside the vehicle, while vehicle is moving. Vehicle speed must be reduced to 2-3 MPH to shift into or out of 4WD low range. The axle shaft disconnect housing is welded to the left axle shaft tube between the differential housing and the spring pad. A splined, two-piece axle shaft is located on the left side and it is mechanically engaged or disengaged by a shift collar that is moved by a vacuum shift motor controlled shift fork. The shift motor is operated by vacuum that is controlled by a vacuum switch located at the transfer case. The disconnect axle vacuum control system consists of a vacuum control switch on the transfer case, an air vent filter, a vacuum shift motor (located on the left front axle tube) a 4WD indicator light and vacuum switch, 2 vacuum check valves, a reservoir and a interconnecting vacuum harness. see scheme 10 See VACUUM DIAGRAMS. The 4WD indicator light located on the instrument cluster is illuminated when the vacuum operated shift motor engages the front axle.
