3.25 gears

[390F100]

Are they decent? What are the advantages to having them vs 4.11 as an example? I need schooling on rear ends, cause today I pulled the tag on my rear end and it is a 28 spline 9in with 3.25 gears...Any Help would be appreciated

[Dragon]

4.11s with 29 inch tall tires will top out at 85 mph at 4400 rpm. The 3.25s will go farther on the same tank of gas. Alot farther. The 4.11s will snap the truck out of the hole and your shift points will come so fast on a strong engine that it will feel like you never wind up in a gear. Until you top out. 3.25s will still take off in 2nd of a NP435 and and top at 140 mph and 4600 rpm

MPH = RPM x Tire Diameter (in inches)
___________________________________

Rearend Gear Ratio x 336

So my 71 is
(4600 x 33)/(3.78x336)

or 119 mph

With 3.25s I will get 139 mph if I have enough horsepower to push the wind drag.

I hope this helps

Your 9" will hold up 600 hp but 28 splines might fail if you drop the hammer at 4000 rpm in a 5280 lb truck.

The 9 inch is a great rear end and parts are still made for it, including a locking differential. An upgrade is the Dana 60 which is about 50% stronger and many come with locking differentials.

[fordman]

grerat answer there dragon. to simplify. the 3.25 is more of a highway type of gear. and the 4:11 is more for pulling heavy loads and working the truck hard.

[390F100]

That is exactly what I was looking for, thanks to you guys I am now a little more education on the ever popular Ford 9".