Mercedes G56 Manual Transmission

G56 Transmission Specs & Ratios

The Mercedes Benz G56 is a heavy duty, 6 speed manual transmission found in various Ram HD pickup and medium duty commercial truck applications. There's often confusion as to when the G56 was introduced to the Ram pickup platform. The G56 was rolled into production alongside the NV5600 during the 2005 MY, where it eventually replaced the New Venture unit altogether. The transmission was not a selectable option for 2005; pickups arbitrarily received the NV5600 or the G56. The aluminum cased G56 is much lighter than the cast iron NV5600 and has a higher input torque capacity. There are many reliability issues with the G56 in cases where engine power is increased via aftermarket add-ons. The cases and gears are known to crack, typically due to flex under heavy load. The G56 also has a relatively short overdrive ratio, which translates into slightly high engine RPM at cruising speed. Beyond that, the transmission is smooth shifting and reliable at its intended input torque.

There has been much controversy regarding lubricant selection, with many owners and industry experts arguing that using ATF+4 to lubricate the transmission, as Chrysler recommends, can cause it to fail prematurely. Mercedes-Benz recommends a thicker 75W or 90W gear oil in their trucks that are equipped with the G56. It is debatable whether anything is gained by switching to a 75W/90W gear oil, but many owners choose to do so. A tooth was removed from the input shaft gear for the 2007.5 model year, resulting in a ratio change for the 6.7L Cummins version. When equipped in 6.7L applications, torque was derated to 610 lb-ft for 2007.5 to 2012 model years, and has been derated to 660 lb-ft for 2013 to current model years. Meanwhile, the Cummins Turbodiesel is available with up to 900 lb-ft equipped with an automatic transmission.

 

G56 Transmission Ratios

Application

1st

2nd

3rd

4th

5th

6th

R

2005 - 2007 MY

6.29 : 1

3.48 : 1

2.10 : 1

1.38 : 1

1.00 : 1

0.79 : 1

6.29 : 1

2007.5 - present MY

5.94 : 1

3.28 : 1

1.98 : 1

1.31 : 1

1.00 : 1

0.74 : 1

5.42 : 1

 

G56 Transmission Specs

Transmission:

Mercedes-Benz G56

Type:

6 speed manual transmission

Manufacturer:

Mercedes-Benz

Predecessor:

New Venture NV5600

Model Years/Applications:

2005 - present Ram 2500/3500 w/ Cummins Turbodiesel

Synchronized:

Synchronized in all forward gears and reverse

Case Material:

Aluminum

Max Input Torque:

N/A, suggested under 700 lb-ft

Weight:

~ 200 to 225 lbs

Fluid Capacity:

4 quarts

Fluid Type/Spec:

SAE 75W/90W gear oil (recommended by Mercedes-Benz), ATF+4 automatic transmission fluid (recommended by Ram Trucks)

Service Intervals:

Replace transmission fluid every 60,000 miles

Features:

• Designed specifically for light and medium duty diesel truck applications

• Manufactured in Brazil

 

NV5600 vs G56 shift pattern

Both the NV5600 and G56 manual transmissions were available
during the 2005 model year - transmissions can be identified by their shift pattern