I am planning on ordering an 05 CTD. I was thinking of getting the 6 speed manual trans, but now that it has been changed to the G56 I wonder about mpg with that vs the auto.

The G56 has a lower OD ratio than the NV5600, so combined with the 3.73 rear end, the only ratio available with the G56, makes the overall drive ratio the same as a NV5600 with 4.10 rear.

Since the G56 is too new to have broken-in mileage numbers, does anyone have NV5600 / 4.10 rear / 4x4 / SRW mileage numbers I can compare with what people get with the Auto / 3.73?

 

If you were never going above 60mph, I would say the G56 would be your best bet. If you are going to be on the highway (70+) for extended periods of time, the auto will probably get better FE because of the numerically lower final drive ratio.

The best highway FE is obtained by keeping your RPM's below 2000.

However, a lot of people put bigger tires on to adjust the final drive number down a little.