I have a 2007.5, 2500 6-speed manual 6.7 liter and curious on how to determine what gear ratio I have in the rear end.

On flat ground at 70 mph, I am @ 2000 rpm with all stock including tires.

 

3.73:1 as, to the best of my knowledge, 4.10's weren't available with the G56 manual transmission.

Greg

 

Look on your window sticker. If you can't find it, mark the side of the wheel and the rear driveshaft. Count how many rotations the driveshaft makes for 1 full revolution of the wheel. 3.5 turns=3.42 gears. 3.75 turns=3.73 gears.

 

You may want to look at the "Pumpkin".
It usually has a tag that gives the ratio.

 

No tagas on AAM axels.If its not listed on the window and you didn't pay extra for it as a option its 3.73.

 

Hey WMRIDER fill out yiour sig.like the rest of us.Make sure of your replys before shooting from the hip.

 

I had an 06 and with the 6sp man and 245/70/17 I was at 60mph at 2000rpm with 3.73. I now have an 07 with the same 6sp and get 63mph at 2000rpm with 235/80/17 and a 3.73 which makes sense because the wheels ar 5% taller. 70mph at 2000rpm doesn't make sense unless they changed the trans or the rear is less than 3.73- I don't think either applies and no stock wheel/tire is going to make that big a difference. I would love 70mph at 2000rpm.

 

Both are possible changes. The G56 DID undergo a change in the overdrive gear in 07.5 when it was mated with the 6.7L (i think from a .79 to .72, though don't quote me on those exact numbers). Also, though i don't know if it was offered in 07.5 but sure is in 08, 3.42 gears are offered with the G56. At 63 MPH, I am currently at 1600RPM. This is with 35" tires and my speedometer calibrated spot-on, verified by GPS. At 70 MPH I am just a hair over 1800RPM and was around 1950RPM @ 70 MPH with the stock tires.

 

Makes perfect sense now that you say they changed 6th gear. I figured I would add my $.02 since I had a manual 06 and now have the same tranny in my 07 with the same gearing. I knew they must have changed the ratios or something else was off. looks like he just has a 3.73 with the new higher 6th.