Manual Transmission: Notes

The S6-650 and the M6HD transmissions are 6-speed synchronized units. The ZF 6-speed has the following features:

• An integral clutch housing
• An aluminum main case, extension housing and intermediate housing
• The mainshaft has 2 tapered roller bearings. Mainshaft end play is controlled by a selective shim located under the bearing cup
• The countershaft has 2 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 helical
• 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 and the M6HD have 6 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
• 1st 3.30:1
• 2nd 2.10:1
• 3rd 1.31:1
• 4th 1.00:1
• Overdrive or 5th 0.72:1
• Reverse 5.23:1