6spd or 48re mileage difference

[WStoops]

Has anyone documented a difference in mileage between a 6sp and a 48 re with a 373 axle? I read on some thread that there is a difference in the final drive ration between the two trannys so the hwy rpms are different even with the same axle ratio.

 

[EEdmondson]

It seems that after reading this forum for more than a year that the people with the 6spd are getting better mileage. It would also seem that cruising at highway speed would give the 48re a slight edge. It has a higher OD: . 069 vs . 073 (. 079 for the G56?) and the 6spd is heavier. Correct me if I'm wrong on any of this information. (In other words don't take these numbers to the bank, I'm taking them off the top of my balding head).

 

[NNelson]

2 cents

I have the truck in my sig. It is an auto. At 65-68 MPH on the highway I get about 18. 5 to 19. If it is a long flat run I have gotten as high as 22-23.



My cousin has a stock 6speed 2500 QC LB 2004 model and at about the same speed he says he is getting about 19.



I have the HO and he doesnt. I have about 13000 miles and he has about 8000. I live in AR and he lives in OR.

 

[DSutton]

I have an 03 6 Speed (305/555) and my dad has an 04 auto (305/555). I have good info on this subject, as it comes up often (For bragging rights over Sunday Dinner). I consistantly get 1-1. 5 MPG better than him. It is more noticeable on highway driving, and the gap narrows with lots of city driving. This is consistant on long hauls, with similar loads, or short runs empty. I do not want to start a mileage war :-{} so I won't ste actual MPG's. :{