I have a 2006 fx4 f150 I've been looking at changing my gear ratio . I have a 6" fabtech lift running 35s . It really struggles going up some good inclines . I've looked at gear charts and either my truck is way off or these charts are because I'm not tacking anywhere near ( I'm about 1900-2000 at 65mph) any thoughts or info on what you guys are running?

 

The 06 FX4 if still stock should of had 373 gears and with the 5.4 you should be fine. I have an 05 with the same and don't have any issues even pulling a 5500 pound boat. Changing gears is a pricey adventure but if lagging you may need to go with 410's if you drive a considerable amount of highway or even higher if you don't.

 

Your speedometer is not accurate with those 35's. You need a programmer to correct it, a set of custom tunes would help a lot. If you change gears, I'd go for 4.56's and you have to change both the front and rear. This is a $2000 job.

 

I have a programmer and thought I dialed it in but probably not . I talked to a guy at 4 wheel parts and he suggested 4.88 . Would this be too high or actually low gearing I would think it would put me at about 2500 rpm with 36" tires

 

4.88's are a bit too much. With 4.56's and 36's at 65 mph in O/D with the converter locked up, it should be doing about 1940 rpm. In 3rd it would be about 2770.

What's the AXLE code on your door jamb sticker?

 

I don't have the info on me right now I'm at work but I did check it a couple months back when I was really looking into things I have a 9.75 rear axle and 8.8 front axle both say with 373 gears . On flat ground the truck runs great . just when I go up inclines I'm talking about 4000 RPM barely pulling 55 mph

 

3.73 to 4.56 is a logical progression.

 

Ive found a few places that have gear packages. F&R with master install kits for both for @900 I don't know anything about nitro gears however.