What gear ratio do I have?
 

Hello everybody, when I purchased my 2005 Limited 6.0l I just assumed it had the factory gears in it which are 3.73s but I noticed the other day that my speedo is pretty much bang on with the 35" tires. Soo that got me to thinking maybe they've been replaced already. It runs right around 2000rpm at 70mph. Thanks for your help.

The computer can be reprogramed to accomidate your oversized tires.

Right, I was thinking that but that's why I posted my engine rpm also.

Your VIN/door sticker will confirm your axle ratio (if it has not been altered).

Yes it does. And the diff tag also says 3.73 but I'm thinking they have been changed.

Maybe I should of asked what is everyone's RPM at 70mph with 35" tires and please list your ratio. Thanks. I'm thinking they are 4.10s.

I'm sure Tom will chime in soon. :p

I hope they have been changed. It wouldn't surprise me too much. The first owner spared no expense on this unit but the second owner was not so good.
Here's a picture for *****s and giggles.
http://i1067.photobucket.com/albums/...ps6ff8da84.jpg

Since that picture I have installed longer home made spring shackles to level it out. :-X22
Also that picture was takin in the middle of winter. The snow is gone and life is good again up here. lol

2000rpm at 70mph is about right. I have stock 3.73's and various brand 315/75's.

Are you comparing to GPS? My 2005 6.0 speedo is off by a little. I also run 35's, I'll pay more attention today on my road trip and re-post. I'm running 3.73's.

Ok did some looking around on the google machine and it looks like the 6.0 superduty guys are running right at 2000rpm with 3.73s and stock tires. And yes I checked with a GPS. Thanks again.

I'm running 70 on the speedo @ 2000 rpm's and actually 72 on GPS.

Thanks for the reply. Ya that sounds like what I'm running. I guess it was wishful thinking. lol.

Well crap looks like I have the factory 3.73. I went and lifted the rear up, marked the tire and drive shaft. Pretty much right on 3 and 3/4 drive shaft turns to one wheel rotation. Oh well, I planned on lockers anyways what's new gears. Lol. Thanks everybody.