Axle Ratio = Crusing speed

[JCockerill]

I recently found out I have the 4. 10:1 11. 5 rear in my 2006 2500. my mpg reading strugles to get above 15mpgs. mostly around town. on the highway i'm seeing the following rpm/mph



2300/75

2150/70

2000/65



what are the guys with the 3. 73:1 rears seeing? is it that big of a difference? I would not normally care , but at $5 a gallon.....

 

[SBeretz]

You must have the manual transmission? I have the older G56 and get about the same as you with 285/75 size tires. I would think you already have 3. 73's. If that is the case, you may want to look at 3. 42's. Scotty

 

[JCockerill]

no, it's the automatic, it deff has the 4. 11's another member looked up the vin for me. it has the 4. 11 gears with the 4 speed auto...

 

[Okie-Go]

I have the 3500 drw and get 21 on the highway quite often. At times it gets a tad better than that

 

[BHolm]

I have a G56 manual and 3. 73 with 285/70 tires. I am at 1900 rpm at 60 mph and I can manage almost 20 mpg. If I run 65-70, like I used to regularly I average around 17 mpg. The key is to stay under 2000 rpm, economy drops rapidly after that.



We also need to make sure we compare apples to apples. 2wd and 4wd trucks are going to have different numbers. 2wd trucks will do substantially better most of the time due to a much lower stance. You also need to have the engine broken in well to see good numbers. If you have towed heavy a lot, it will take 20-25k miles. If you mostly just drive empty I think it can take 35-40k miles to see good milage numbers.

 

[SBeretz]

Sorry I thought you were talking about the new 6 speed auto. I would think a set of 285-75's would really help you out. They helped for about 200 rpms for my truck.

 

[firemansdiesel]

I have 35" tires w/ odometer re-done w/ my 3. 73 auto as follows:



65mph= 1700

70mph= 1800

75mph= 1900



I get 16/17 mpg in city/backroads and 18-20 freeway. That's cruise set on 75mph on I-5.

 

[JCockerill]

would the 3:73's really make that big of a difference for me? i have 256/70's on it now, when it's time for tires i will deff go bigger

 

[prmizeski]

I had the same exact readings in terms of rpm with the 265/70's. Best single purchase, Smarty Junior from Bob Wagner for mileage. 40 HP setting getting me 1. 6 MPG more, hand calculated with mostly highway travel for an average of 17. 6 mpg. Driveabilty greatly improved.

When its time go with the taller tires and enjoy your 4:10' s!

 

[JimScott]

I have a G56 manual and 3. 73 with 285/70 tires. I am at 1900 rpm at 60 mph and I can manage almost 20 mpg. If I run 65-70, like I used to regularly I average around 17 mpg. The key is to stay under 2000 rpm, economy drops rapidly after that.



We also need to make sure we compare apples to apples. 2wd and 4wd trucks are going to have different numbers. 2wd trucks will do substantially better most of the time due to a much lower stance. You also need to have the engine broken in well to see good numbers. If you have towed heavy a lot, it will take 20-25k miles. If you mostly just drive empty I think it can take 35-40k miles to see good milage numbers.

I'm right in there with your numbers even though I have a NV 5600 transmission. I can get close to 20 if I only run about 55 MPH. However, on the freeway you will get run over at that speed so at 65-70 I get about 17 to 18.

Jim