YOu have 4.10's

Here's the formula I use:

(tire dia X RPM) / (336 X trans ratio X axle ratio) = MPH **336 is a constant # used for this formula****

In your case (with 315's)

(34.5 X 1900) = 65550 / (336 X .73 X 4.10) = 65.18 MPH

If you had 3.73's the same calculation gets you 71 MPH at 1900 RPM...dealer is wrong...you have 4.10's.

 

Have the service Dept run the Vin # and print out the build sheet. It looks like we may have solved your poor fuel mileage issue.

 

The dealer did run the printout. It says 3.73 Now what do I do? Is there a different gear ratio in the 06 trannys?

 

P.S. Swap out the fuel filter every 5k mles! This helps more than you know!

Rick

 

yes. The G56 started appearing mid 05.

 

We had a similar problem on a old 84 ford F-250. Everything said the truck had a 460 in it, but when it came time to tune it up we had issues getting parts. Come to find out it had a 471 in it, medium duty engine in it. That truck would run, it would definetly hall a load. I would ask them to open the rear diff cover, and double check it, or try to find some kind of tags.

 

I think you fine the g56 has a .79 6th gear. the gear calculator say 66mph@1900rpm. I used the wrong transmission numbers last time I calculated (nv5600).

I posted a gear calculator earlier in the thread.

 

I have 4.10s in my 05 auto and get around 18.5 mpg running at 70 city and highway combined. I get about 16.5 running 77mph though. I think I am at about 2100 rpm at 70mph. Stock tires. No performance mods yet.

 

So I guess that means I do have 3.73's with a g56 tranny. Where can I find out the info on the differenttrans. Now that I somewhat more informed on that my next question is what module/ chip/ flasher/ do you recomend for towing and economy???? Thanks

 

just google the modle numbers on the trannies and you will find info. I pulled the g56 ratio's from this page.

http://trucks.about.com/od/2005picku...er_wagon_2.htm

As for performance there are a boatload of them. If you can afford it I really like my juice. Smooth power, low egt's, gauges, easy install. unless you want more than 100hp I think it is the best product. over 100hp I test to like the TST. with 10 different power and torque levels the ajustablitly of it is just unmatched. those are opinion's of course.

here is a link to a matrix of how the boxes make there power. it gives a good list of what is out there. it is a work in progress though so if you see a question mark it mean that that is unknow to me.

http://home.comcast.net/~beardrobert..._matrix_V3.pdf

 

Your truck is a 06 6 speed, so it has 3.73's... no other option. Overall gearing in 6th is nearly identical to the NV5600 with 4.10's.

Your mileage will get better with break in... I have 12k on my 05 and am getting about 2 mpg better than when I bought it. In the meatime if you want to get good MPG's just keep your terminal speed low and don't use the brakes. Everytime you use the brakes you just turn diesel fuel into heat and brake dust I get a lot better economy running at 70 than 80. I don't think accelerating hard really hurts anything, unless you're spinning the tires.

 

I can't thank you all enough for all the help and input I recieved on my very first post. This forum is the best. CW