Alright I've owned my F350 for about a year now and I'm wanting to go a bit lower with my axle ratios. Its a e40d with 3:55's sitting on 37" tall tires. I know the added lugging is probably doing wonders to my transmission as well. So what would you guys suggest? By my quick math 4.56s are pretty close to stock with the 37's. Opinions? I know there are alot of OBS fords sitting a bit taller then stock.


Thanks in advance.

 

3.55 gears are marginal with stock tires on an OBS.

I'd go with 4.10 instead of 4.56 with 37" tires.

 

id go with 4.56's. i got 4.10's and 35's and theyre a little doggish down low that extra little oomph in the bottom end would be nice. hence why i got 4.56's sitting in the kitchen ready to go in for when i put the 37's on

 

ive heard many variations, most common being 35's+4.10 and 37's+4.56 gears. I have 35 inch tires with the factory 3.55 gears and its a pooch on the low end and at 65-75 mph it sits at 2,000-2,200 rpm with a zf5 tranny.

 

I found 'stock' to have too much gear (i.e. 4.10's and 31" tires). Upping to 35" tires made me happy as far as highway speeds.

4.30 ratio is quote common in the 99+ Fords.... might get a deal on some good used gears.