Transmission Description

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 Moly 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