Manual Transmission

The S6-650 ZF transmission is a six-speed synchronized unit. The ZF six speed has the following features:
^ An integral clutch housing.
^ An aluminum main case, extension housing, and intermediate housing.
^ The mainshaft has two tapered roller bearings. Mainshaft end play is controlled by a selective shim located under the bearing cup.
^ The countershaft has two tapered roller bearings. The countershaft end play is controlled by a selective shim located under the bearing cup.
^ The countershaft is serviced as an assembly.
^ Synchronized in all gears.
^ All gears are bevel cut.
^ All gears, including reverse, turn on needle roller bearings.
^ Single-piece shift forks with molly coated pads.
^ Internal oil pump, driven by the countershaft, to supply transmission fluid to an external cooler.
^ Provisions for mounting a power take-off unit.
^ A reverse idler gear that does not need to be removed during disassembly.
^ The mainshaft and countershaft are assembled under preload. If the ZF transmission is disassembled, a preload measurement must be taken.
The S6-650 ZF has six forward speeds that feature a LOW gear for take-off under heavy loads and a OVERDRIVE gear for highway driving conditions. The gear ratios are as follows:
^ Low 5.79:1
^ First 3.30:1
^ Second 2.10:1
^ Third 1.31:1
^ Fourth 1.00:1
^ Overdrive 0.72:1
^ Reverse 5.23:1