new truck auto vs. 6-speed

[KS_Cummins]

Need some advice here. Trying to pick out an 05 and trying to decide between auto and 6-speed. Primary concern here is overall mileage, not towing. From driving an auto and 6-speed (the newer Getrag) back to back, the 6-speed was running 2-400 RPM higher at highway speed than the auto, both had 3. 73 gears.



What is the best choice here? Will be a 2500 QC SB 4x4, 3. 73 gears, towing up to 6K lbs 6-7 times year, rest of time DD. I don't mind rowing my own, do it on everything else.



I looking for advice on what will result in best mileage, not necesarily the pros and cons of driving one or the other in daily driving. And want to not **** off the moderator.

 

[john3976]

Just a slight correction but the 2005 new 6 speed is not a Getrag, it is the G56 designed by Mercedes.



Second as for the mileage, I get about 22 MPG unloaded on the road and upwards to 18 in town unloaded.



I have a 8 x 24 extra height enclosed car hualer trailer and at about 10,000 pounds I can still get 14 MPG. That is still new and not fully broken in, mileage should go up a little from what I hear.



I have an Automatic in my 2005.

 

[klenger]

I suspect that the milage will be pretty much the same between the two. What you loose in milage with the final gear ratio with the G56 you make up in trans efficiency. I suggest you get the transmission that you really want to drive. For me, that would be the six speed.



You can see how gearing affects RPM with the two trannys using this Excel worksheet: http://www.klenger.net/dodge/general-reference/gear-speed-calculator.xls

 

[BHolm]

If I wanted a six speed I would either wait a while and see how the G56 holds up, or search out a NV5600 equipped truck. The 5600 is well proven and I think has a taller OD gear than the G56. I just don't like the stories I hear about the G56 like oil leaks, underfilled but topped off through the shifter??? as a fix? I have three trucks with the 3. 73 auto and 6-7000 lbs is childs play for these trucks regardless of transmission. Milage is likely to be very similar. Buy the one you like because 1-2 mpg difference, if it exists, won't be enough to make up for your satisfaction or lack there of. I see no reason to not buy the 48re or the NV5600. I am personally somewhat concerned about the long term reliability of the G56 and would not buy one yet. Of course with your usage you will not be working it very hard and it would likely be fine. For reference my '05 48re 3. 73 truck averages 18 mpg. I can get 20 if I run 65 mph. I get about 13 towing 7-8000 lbs running 70-75. Higher speeds start costing you in milage, loaded or empty.