In the 70's Jeep had Quadra-Trac transfer case, which was chain drive, full-time 4WD, with a high and low range planetart reduction unit, and a "emergency" drive capability (which locked the limited slip differential in the transfer case)
Later on came the Selec-Trac system which is a full-time/part-time transfer case with shift on the fly. (The was also a Command-Trac part time transfer case)
This was optional on XJ Cherokees
Then came Quadratrac II on the Grand Cherokee, which is the same operation as Selec-Trac, but a few different transfer case models were used over the years.
Quadra Drive is the latest system which uses the same transfer case as QuadraTrac II and adds limited slip/locking gerorotor differentials front and rear, and is quite a capable system.
-Andy W
Quadra-Drive.
Quadra-Drive.
Quadra-Drive