I have a 2008 FX4 level 1... I have one of the axles that seems to taper off at the ends near the drum brakes, i could go and measure it no prob just not sure of the measurements for the 28's and the 31's. So any help to find out what i have woul be great.

Also, Need to know what the biggest gears i can run are in each setup. i plan on running 35's eventually but 33's for the most part so i was thinking of doing 4.56's just need to make sure they will fit in whatever axle i have!! thanks guys

 

i have 4.88's and they fit in both ends an it is the lowest gears you can get for the front d35. all 8.8 gears are the same no matter what the spline count. i have 33's and plan on going to 35's eventually thats why i did 4.88's.

 

I thought the only 31 splines were in the fx4 level 2's. I'd say you have a 28 spline

 

damn well i need to know for sure before i order gears lol

 

Its a 28-spline axle. That has nothing to do with what gears will fit though. An 8.8 is an 8.8 when it comes to the ring and pinion.

 

Level II's did not exist in 2008/9 but the FX4 of those years will have either standard 28/Traction Lok or optional 31/Torsen.

Measure the axle tube inboard of the springs. 31-spline is 3 1/4" diameter or you can measure circumference by wrapping a string around the axle tube, marking it and measuring the string. 3 1/4" diameter corresponds to about 10 1/4" circumference.

28-spline is noticeably smaller.

 

so your saying just what t5cents said.. i can throw 4.88's in there if i wanted? and if so.. how would those be with 33's? until i got 35s

 

its not bad...im at about 3000 at 70 on the hwy in 5th tho...

 

4.88's would be fine with 33's.

 

canada still had the FX4 in 2008 (bastards) but yeah you can run 4.88s no problem just make sure you do F+R at the same time or if you do rear only for now don't put it in 4x4 lol

 

I ran 4.88s and 33s without any intention to change it, in my sport trac (4.0L sohc auto).

 

do i have a d35 int he front.... FOR SURE? cuz i went to order gears and the guys at the shop said theres a few different diffs for my year truck.. ugh i just need to order gears but its so difficult apparently

 

Yes, D35.