DESCRIPTION & OPERATION
Note. For front differential integral housing servicing procedures, see DIFFERENTIALS & AXLE SHAFTS - FRONT INTEGRAL HOUSING article.
Automatic Disconnect Differential (ADD) allows engagement of front differential from 2WD to 4WD while vehicle is moving. On vehicles with ADD, a flange is mounted on the front hub which is splined onto axle shaft connected to side gear shaft on front differential. Locking hubs are not used with ADD.
On Tacoma and 4Runner models, when transfer case is shifted into 4WD, ADD is shifted into 4WD by operation of ADD solenoids which control vacuum supply to ADD actuator. On Tundra models, the ADD actuator uses an electric motor. On all models, ADD actuator engages clutch sleeve with intermediate shaft in front differential and side gear shaft, providing 4WD operation. When vehicle is in 4WD, 4WD indicator light on instrument panel will be illuminated.
Note. ADD solenoids may also be referred to as ADD Vacuum Switching Valve (VSV).
Operation of transfer indicator switch or 4WD switch completes ground circuit which allows ADD relay to operate. When ADD relay operates, voltage is supplied to ADD solenoids. ADD solenoids operate and control vacuum supply to ADD actuator for 4WD operation. (Scheme 15)or (Scheme 16). On Tundra with Touch Select, the 4WD control ECU supplies voltage to the ADD solenoids.
