Last summer I added a level kit and went to some 275/60R20's on my Ecoboost FX4. It has a 3.73 from the factory, but was considering a ratio change to 4.1.

I did see some 4.3 options; If i wanted to go as tall as a 4.3, would there be any issues with the Ecoboost pushing this? No Tune at this point in time, although I would probably need one when the ratio changes.

Any recommendations on manufacturers for ring/pinion sets?

From what I read, the rear looks to be the 9.75 and front is the reverse 8.8 spline. If I can get validation, it would be helpful.

Finally, I assume I would also need a diff rebuild kit when I did this... or is that a waste of money? New bearings? Just passed 90K miles on the truck.

Thanks!

 

I don't believe you can get 4.30's for the front.

The Ecoboost has so much low end torque that I don't think a ratio change, even with bigger tires than stock, will do much for you. Not worth the $$$ if you ask me, 3.73's are fine.