Michael7166

How can I tell what gears my truck is using now without dismantling anything?

05 super

check your driver's door jamb for one of these numbers


Axle Decoder Chart

Code Ratio Capacity Maker Type Yr

12 2.73 3800 FORD REG 1991
17 3.25 3300 FORD REG 1971
17 3.31 3800 FORD REG 1995
18 3.08 3800 FORD REG 1991
19 3.55 3800 FORD REG 1991
25 4.10. 5300 FORD REG 1991
29 3.55 5300 FORD REG 1991
35 4.10. 6250 FORD REG 1991
36 3.73 7400 DANA REG 1980
39 3.55 6250 FORD REG 1991
45 4.10. 7400 FORD REG 1991
49 3.55 7400 FORD REG 1991
65 4.10. 8250 FORD REG 1991
69 3.55 8250 FORD REG 1991
72 4.63 11000 DANA REG 1991
73 5.13 11000 DANA REG 1991
H5 4.10. 3800 FORD LIMITED SLIP 1991
H7 3.31 3800 FORD LIMITED SLIP 1995
H8 3.08 3800 FORD LIMITED SLIP 1991
H9 3.55 3800 FORD LIMITED SLIP 1991
B5 4.10. 5300 FORD LIMITED SLIP 1991
B9 3.55 5300 FORD LIMITED SLIP 1991
C5 4.10. 6250 FORD LIMITED SLIP 1991
C9 3.55 6250 FORD LIMITED SLIP 1987
D5 4.10. 7400 FORD LIMITED SLIP 1991
F5 4.10. 8250 FORD LIMITED SLIP 1991
W5 4.10 8250 FORD LIMITED SLIP 1995


these are old codes but they should still work. look for a number/letter from the left column and match your door jamb cod with it. good luck

NORCAL SS

they make 4.88s ?

05 super

maybe this is better
https://www.f150forum.com/showpost.p...06&postcount=2

05 super

i'm sure some aftermarket vendors make a 4.88. they may even have been offered in the super duty's as an option

Michael7166

my code is B6....3.73

Is that good, bad or indifferent?

I have 4 wheel drive, but do not fully understand the implications of what I have.

Could someone break it down in layman's terms?

Schertz7

it means for every time your rear wheel makes a complete revolution your drive shaft makes 3.73 rotations. The higher that number is the more low end torque you will have, but lose your top end speed and most times fuel economy. 3.73 is an ok gear ratio for a factory truck with factory sized tires. most lifted trucks with 35's will go with 4.11's just to make up for the larger diameter of the tires

HondaMoto799

i have 4.10's and i run 35's..its a big difference from the 3.55's still little sluggish on big uphills, but that could be cause i got a 4.6

IMO for 35's
4.10 = Lots of highway and not much towing
4.56 = Lots of streets,Towing and, If you live in a real hilly area also more power

Schertz7

yeah thats the common two gear ratios, never installed anything higher than 4.56 in a F150, its just unecessary. Hope that helps!

chad085

heres a little equation to help determine what gears for bigger tires...

new tire diameter X current gear ratio = ratio needed to duplicate stock
old tire diameter

for example, i went to 35's from my stock 29's, a 1.2068..... percent change, multiplied by my stock gear ratio of 3.55 gave me a number of 4.2844.....

since there is no such gear as a 4.28, so the options are 4.10 and 4.56. Having an overdrive trans, and occaisonally towing, i opted to go down (numerically up) to a 4.56. This put me at about 100-200 rpm's higher than stock while travelling 70 mph in overdrive, which in my opinion ain't bad. I'm pretty sure they do make a 4.88 for the IFS 8.8, i can't remeber which company it is though, but you wouldn't need that unless you had like 38's or bigger, which is too big for that axle anyways.