G56?

[Midnight]

Afriend is looking at purchasing a 2005 3500DRW 4x4. It has only 19000 kilometers is in mint condition and is loaded(Laramie Sport). He will be getting it at a very good price. His only concern is higher rpm level's at highway speeds. What do you guy's think? How much difference in mileage will there be say vs my 2003 5600 w/3. 73? Thanks in advance.

 

[mberry]

The biggest difference in mileage will come from the programming in the ECM in the '05 vs your '03, not the transmission. The higher RPM will not hurt the engine at all.



What gear ratio does the '05 have. If it has 3. 73's then it will get slightly better mileage than 4. 10 all things being equal. Mileage really depends a lot on how it is driven too.

 

[msperos]

The 3. 73's with a G56 speed is about the same final drive ratio as 4. 10's with the NV5600. I'm getting a steady 15mpg's with my 05' the 3rd injection event coupled with the gearing really effects the mpg

 

[Midnight]

Any more than just responses?

 

[Mishkaya]

Midnight

I am not sure what mileage you are getting with your 03, but I have an 05 with the G56, and I can get around 16 in town (winter fuel) if I don't go over 65. However, as soon as I make a long highway drive at 70-75, the mileage drops. At 70 my mileage is just under 15, and at 75 it is barely above 14, and this is empty. At 70 rpm's are 2250, if this gives you any idea. I also have an 02 auto with the 3. 54 gears and I get an average of 18 mpg at 70 (1900 rpm) on the interstate. I have found the gear ratio on the G56 to be very disappointing, like everything esle about the truck. I am currently awaiting the US gear overdrive unit for the G56 impatiently. Sorry for the long post.

mishkaya

 

[MickeyMiller]

Midnight,



I have a '03 with5600 and 3. 73 and have been running between the SF bay Area and LA for the past 4 months. RPMs don't make much difference in MPG but speed does. I have run it at 65 in both 5th and 6th and get almost the same milage. At 65 mph on I-5 I can get hand calculated 20. 4 mpg. At 75 mph in 6th it drops to 18. 7 mpg. I am running a Edge box on level 2 which I think helps a little, but speed is definitly the deciding factor in MPG.



Mickey

 

[cerberusiam]

On the average 3 to 4 mpg less than your 03. If mileage is a concern then DON'T get a dualie or the G56 with 3. 73's.

 

[mdepot]

I've got a 4x4 with an NV5600HD and 4. 10's (about the same as a G56 and 3. 73's). At my last job I was taking back roads to work and drove mostly at 45-50 MPH. I was averaging 20-21 MPG, really. And that's calculated from fillups, the trip computer usually said 21-22.



Now I have a new job and I'm on the highway all the time driving mostly 65-75 and the mileage went down to about 16-17. To me the RPM's "sound" too high at that speed, even though it's not really a problem.



I'm planning to put bigger tires on it anyway, which would act like swapping in numerically lower gears. That might be something your friend could consider.