Ive got a 2010 f150 2 wheel, my rear dif grenaded on me. I'm looking to just do a whole rear end swap. It's geared 9.75" x 3.55. Im having a hell of time finding a used 3.55. The 3.73 is widely available and I've seen a couple 3.15s around. I've spoke with a couple different people and got different answers on weather or not i could use a different gearing ratio without causing other problems. Input would be appreciated thanks.

 

a gearing change is usually taken care of via a tune. A quick google search shows forscan can do it on later trucks but Im not sure about 2010. I would look into that, at ~$65 for a dongle its far cheaper than a tuner

 

speedo and odometer would be slightly off. not a big deal. I myself would go with the 373s. way better for towing.

 

agree, but OP, if youve gone (or plan to) slightly bigger tires the lower gearing, 3.73, will be will be not only an advantage, but will get you back close to stock. Bigger tires, lower gearing.

 

I actually have much larger tires on there then stock and I knew the speedo was off a few mph. So that sounds idea actually. So your saying I don't have to worry about the tune or transmission?

 

Correct, if you already have larger tires, the lower gearing, 3.73, will get you back, or at least closer, to stock performance than you have been. And get your odometer/speedometer closer than what they've been.

you can do the math, percent of tire size changes vs percent of gearing change, to see how close you're back to stock, if you want to go to the trouble.

the lower gearing will give you more ump than what you've had with the bigger tires.