The ZF S6-650 six-speed manual transmission first became available in GM's 8.1L & Duramax equipped 2500HD/3500 series pickup trucks beginning in the 2001 model-year. Lower cost, improved fuel economy and a performance advantage in certain situations are among the more important reasons owners express when selecting the ZF six-speed. The S6-650 is also available on C4500 & 5500 medium duty trucks.
ZF S6-650 Key Features:
- Designed specifically for high torque pickup trucks.
- Synchronized in all gears.
- Dual-cone synchronizer in 2nd and 3rd gears.
- High helix angle gearsets provide high contact ratio and quiet operation.
- Lower shift forces w/ tight shift pattern.
- Lightweight integrated aluminum housing
(front, center & rear). - Center bearing support for improved durability.
- Reverse & 1st gear location improve maneuvering ease.
- Overdrive 6th gear shift lever position located forward and away for improved passenger comfort.
- Gross Combined Vehicle Weight Rating up to 26,000-lbs.
- Left & right ISO/SAE 6-bolt Power Take-Off ports.
http://www.thedieselpageforums.com/p...650-ratios.jpg