ZF S6-650 & S6-750 Transmissions

ZF 6 Speed S6-650/S6-750 Transmission Specs & Ratios

The ZF S6-650 and S6-750 are a series of heavy duty manual transmissions used in various diesel pickup applications. The S6-650 was introduced for the 1999 model year in Ford's new Super Duty platform. Ford would offer the transmission until the 7.3L Power Stroke's retirement after the 2003 model year. The stronger S6-750 would replace the S6-650 for 6.0L Power Stroke engines beginning in the 2003 model year. Ford continued to offer the S6-750 behind the 6.4L Power Stroke until the 2011 model year when the 6.7L Power Stroke was introduced without a manual transmission option. The S6-650 was also offered in Chevrolet Silverado and GMC Sierra pickups powered by the 6.6L Duramax diesel from 2001 through 2006.

The gear ratios between the ZF S6-650 and S6-750 are identical. While the transmission is a true 6 speed unit, its forward gears are labeled L-1-2-3-4-5, distinguishing its relatively low true 1st gear. The input shafts are different on the 650 and 750 models, thus they are not interchangeable. Both transmissions utilize an integrated oil pump and external transmission cooler, a unique feature for a manual transmission that promotes adequate bearing lubrication and protection. The fully synchronized transmissions are quiet, offer smooth shifting with positive engagements, and have not been the subject of re-occurring problems.

ZF S6-650 & S6-750 Ratios








5.79 : 1

3.30 : 1

2.10 : 1

1.31 : 1

1.00 : 1

0.72 : 1

5.23 : 1

ZF S6-650/S6-750 Manual Transmission Specs


ZF S6-650 & S6-750


6 speed manual transmission


ZF Friedrichshafen AG


ZF S5-47

Model Years/Applications:

ZF S6-650

1999 - 2003 Ford Super Duty, 7.3L Power Stroke
2001 - 2006 GMC Sierra/Chevrolet Silverado, 6.6L Duramax

ZF S6-750

2003 - 2010 Ford Super Duty, 6.0L & 6.4L Power Stroke


Synchronized in all forward gears & reverse

Case Material:


Max Input Torque:

ZF S6-650

530 lb-ft

ZF S6-750

> 560 lb-ft


ZF S6-650

26,000 lbs

ZF S6-750

30,000 lbs


~ 235 lbs

Oil Capacity:

ZF S6-650

5.5 liters, 5.81 quarts

ZF S6-750

6 liters, 6.34 quarts

Fluid Type/Spec:

Ford calls for MERCON V ATF
GM calls for TranSynd synthetic transmission fluid
Recommend Amsoil Signature Series full synthetic ATF

Service Intervals:

Replace transmission fluid every 30,000 miles of normal operation or 15,000 miles under "Severe Duty" conditions


• Integrated oil lube pump circulates fluid through transmission cooler and lubricates bearings, a feature not typical on manual transmissions
• ISO/SAE 6 bolt PTO provisions (S6-650 has single PTO, S6-750 has dual PTO)
• 2nd and 3rd gear feature dual cone synchronizers

Shift Pattern:

ZF 6 speed shift pattern