It looks like Ford has re-rated most of it's gear ratios, since the order guide shows taller gear options for the Job 3 builds. I have a friend that I'm helping configure an order for an '08, and based on the weight of her trailer and camper, I'm leaning towards having her get the 3.55s for a potential mileage boost (over the 3.73s). Anyone seen what the 3.55s are rated for versus the 3.73s?

BTW: she was leaning towards a GMC dmax/ally and then I gave her a rack-up comparison sheet (quite unbiased even...) of the Ford vs. GMC. Then we did test drives -- 1st time I've been in the 6.4. WoW!! I don't know about this "break-in" lack of power theory I've read about, 'cause the one we drove felt every bit as quick as the dmax -- these things rock!!

Depending on the type of driving (traffic/hills/city), the 3:73 may yield better fuel mileage. And I believe the tow rating is based mostly on the suspension parts. The taller gear will give a much better "comfortable" tow experience IMHO

I'm confused- what model/motor are we talking about? I just built both in GM Autobook, and the tow rating stays the same with either gear set in a F250 4X4.

polarbear said:

I'm confused- what model/motor are we talking about? I just built both in GM Autobook, and the tow rating stays the same with either gear set in a F250 4X4.

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Sorry, been away for awhile... 2008 6.4 -- yup, they give both the same rating...

We ordered her truck after the new year with 3.55s (customer service sux if it's not Ernie, IMHO)...

Thanks! Those gears actually make sense- the diesel is all about low end grunt, and the 6.4 eliminated that "spool up" lag the 6.0 had. We're kinda wondering if GM will follow here, since the 6 speed Allison just gives a deeper low.

Yeah, that was one thing that bugged me on my Dmax/Ally -- it made all this low rpm torque, yet would always downshift if you even breathed on the throttle under 1500 rpm. The Ford will lug down to 1200 rpm and many times will pull up from there if you roll on the throttle...

The final drive ratio was curious to me as well. I never missed the 6th speed in my Ford vs. the Ally's. The rpm on the Ford at 60 is a little more than what a 6 speed Ally is and lower than my 5 speed Ally was.

So IMO they'd have to change the down-shift strategy as well if they add a 3.55 option (and I bet they do too).

There may be changes like that coming because of the fuel mileage complaints of the 6.4.