Mercedes-Benz G56 6-Speed Manual
Type
Manual
Speeds
6
Years
2005-2007
Builder
Mercedes-Benz
Paired with: Dodge Ram 2500-3500, 24-valve Cummins (final years)
Simplified torque-flow diagram — where this transmission sits in the drivetrain, not a literal cutaway of its internals.
Phased in during the 2005 model year to replace the NV5600, the G56 was the last manual transmission behind the third-generation Ram's Cummins before the 6.7L arrived. It is a robust design but was not free of its own issues.
Strengths
- Widely regarded as a strong, well-engineered manual for its era, sourced from Mercedes-Benz's own heavy-truck parts bin rather than adapted from a lighter application.
- Replaced the early NV5600's known weak points with a different, generally well-regarded design.
Known weaknesses
Dual-mass flywheel failures are a documented issue.
Note: A single-mass flywheel and matching clutch is a common aftermarket replacement.
Input shaft bearing problems and bellhousing cracks are documented failure points.
Note: Inspect during clutch service; address proactively on high-mileage or heavily used trucks.
There is some disagreement in the diesel community over the correct gear oil, and using the wrong fluid has been linked to related failures.
Note: Use the fluid Chrysler specifies for this transmission, not a generic gear oil.
Sources
- G56 manual transmission (Wikipedia) (accessed 2026-09-22)
- G56: Last of a dying breed (Transmission Digest) (accessed 2026-09-22)