i have an 02 screw 4x4 with 315/75/16 with 3.55 gears and i want to switch to 4.10 gears and i was wondering where can i buy a kit

 

Do a search for 4.10 ring and pinion for a ford 9.75" rear end, hundreds of places will come up.

 

You will also need a front kit for the 8.8 reverse cut axle or you won't be able to use 4wd.

If you have a 5.4, the rear is 9.75 but if you have a 4.6 it's a 8.8. Check the tag on the axle to confirm, you will see a 88 or 975 on the tag.

 

Summit. Doing my kid's right now, best price and most complete kit. The quality is good-no china crap.