Newbie with Rear-End question

[Mason73]

GREETINGS EVERYONE, I AM VERY NEW TO THE POWERSTROKE GAME…..I HAVE WANTED ONE FOR QUITE SOME TIME AND HAVE FINALLY CONVINCED THE WIFE AND GOT THE GREEEN LIGHT. I WENT FRIDAY NIGHT TO THE LOCAL FORD DEALERSHIP AND WORKED WITH THE FLEET DIRECTOR ON BUILDING THE RIGHT TRUCK FOR MY NEEDS. I WOULD LIKE TO GET SOME IDEAS FROM YOU ALL ON THE AXLE RATIOS, IT WILL BE A CREW CAB 4X4 6.7L AND ALSO MY DAILY DRIVER SO FUEL MILAGE IS IMPORTANT. ALSO IN THE NEAR FUTURE I WOULD LIKE TO GET A 5TH WHEEL TRAILER APPROX 32-36FT WOULD I BE BETTER OFF GOING WITH THE 3.31 OR SHOULD I GET THE 3.55 REAR-END. THEY ARE HOLDING OFF ON THE ORDER TILL I CAN FIGURE THIS OUT….THANK YOU IN ADVANCE
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[Gatorstroke 6.0]

get the 3.55 they will be much better for towing that 5th wheel and i dont honestly think you will see that big of a fuel mileage difference between the two when in town driving not towing. but wait for someone that owns a 2011 to chime in to make a decision

best of luck with your choice wish i could afford a 6.7

[ups 6.0]

3.31 gear with stock 18" wheels/tires @ 70 mph-1500 rpm
3.55 gear with stock 18" wheels/tires @ 70 mph-1900 rpm
3.55 gear with stock 20" wheels/tires @ 70 mph-1700 rpm
IMO...it depens on the size of the wheels/tires you are going with ! As my sig stated...I have 3.55 with 20" wheels,I tow 28ft 5th wheel and a open dirt toys trailer behind that....around 13,000lbs and she's not even breathing hard
Just my .02....good luck

[jasonmt]

Originally Posted by ups 6.0

3.31 gear with stock 18" wheels/tires @ 70 mph-1500 rpm
3.55 gear with stock 18" wheels/tires @ 70 mph-1900 rpm
3.55 gear with stock 20" wheels/tires @ 70 mph-1700 rpm
IMO...it depens on the size of the wheels/tires you are going with ! As my sig stated...I have 3.55 with 20" wheels,I tow 28ft 5th wheel and a open dirt toys trailer behind that....around 13,000lbs and she's not even breathing hard
Just my .02....good luck

The actual RPM numbers look like this though:
3.31 gear with stock 275/70R18 wheels/tires @ 70 mph-1637 rpm (629 Rotations/Mile * 1.16666 Miles/Minute * 3.31 Rear End gear * 0.674 Sixth Gear)
3.55 gear with stock 275/70R18 wheels/tires @ 70 mph-1756 rpm (629 Rotations/Mile * 1.16666 Miles/Minute * 3.55 Rear End gear * 0.674 Sixth Gear)
3.55 gear with stock 275/65R20 wheels/tires @ 70 mph-1689 rpm (605 Rotations/Mile * 1.16666 Miles/Minute * 3.55 Rear End gear * 0.674 Sixth Gear)

Not enough difference between the 3.31&275/70R18 and 3.55&275/65R20 to even worry about, buy whatever suits your style and pocketbook. The factory fit 275/70R18 Conti tyres are notorious POS's though.

[Mason73]

Thanks Guys for the feedback, the order was placed yesterday I went with the 3.31's. I guess it's pretty late for special orders per the fleet director and he wasnt even sure if we could still put in for 2011. I guess if Ford accepts it we'll get a confirmation in about 3 days.....I'll keep my fingers crossed!

[jasonmt]

Originally Posted by Mason73

Thanks Guys for the feedback, the order was placed yesterday I went with the 3.31's. I guess it's pretty late for special orders per the fleet director and he wasnt even sure if we could still put in for 2011. I guess if Ford accepts it we'll get a confirmation in about 3 days.....I'll keep my fingers crossed!

Your guy is either confused or ill informed, you still have ~7 months before the 2011 SD cut off:

Originally Posted by PowerStrokeHD

Tentative schedule is as follows...

2011 Super Duty

05/06/11 - MY11 Final Orders Due
07/01/11 - MY11 Job Last


2012 Super Duty

03/28/11 - MY12 Order Bank Open
07/11/11 - MY12 Job 1

[richc22a]

Originally Posted by Mason73

GREETINGS EVERYONE, I AM VERY NEW TO THE POWERSTROKE GAME…..I HAVE WANTED ONE FOR QUITE SOME TIME AND HAVE FINALLY CONVINCED THE WIFE AND GOT THE GREEEN LIGHT. I WENT FRIDAY NIGHT TO THE LOCAL FORD DEALERSHIP AND WORKED WITH THE FLEET DIRECTOR ON BUILDING THE RIGHT TRUCK FOR MY NEEDS. I WOULD LIKE TO GET SOME IDEAS FROM YOU ALL ON THE AXLE RATIOS, IT WILL BE A CREW CAB 4X4 6.7L AND ALSO MY DAILY DRIVER SO FUEL MILAGE IS IMPORTANT. ALSO IN THE NEAR FUTURE I WOULD LIKE TO GET A 5TH WHEEL TRAILER APPROX 32-36FT WOULD I BE BETTER OFF GOING WITH THE 3.31 OR SHOULD I GET THE 3.55 REAR-END. THEY ARE HOLDING OFF ON THE ORDER TILL I CAN FIGURE THIS OUT….THANK YOU IN ADVANCE
*

You picked a good year to convince your wife that you had to decide which rear end was important....my wife kept telling me that we could not afford one. I told her that it might be time to start checking out a new rear end! And you can see what I am driving!!!

Sometimes, they need a little.."perspective".