How to on axle ratios

[DennyB]

Hey, This question comes up alot and its alot of typing so I thought I would put it here...


The most accurate way to tell the ratio is to remove the inspection plate. There are numbers stamped on the ring gear. Like 48 13. Divide the small number into the large one and that would be the ratio.
Example" 48 / 13 =3.428 IE a 3.43:1 ratio.

Sometimes there is a tag on one of the cover bolts with the ratio on it. This could even be on the front axel(with a 4WD).

Another way is to do this is....
With an open rear (non posi)- jack up one rear wheel (please use jack stands), put the truck in netural, turn the rear wheel and count how many times the drive shaft turns.
Multiply the turns of the drive shaft x2 and divide for the ratio. This is most accurate if you turn the wheel about 10 times.
With a posi rear, jack up both rear wheels and turn the same way as above. use the actual drive shaft revolutions with a posi.

With both wheels off the ground a posi will spin both wheels the same direction.
With an open rear the wheels will spin opposite directions and also do so easily with truck in park.


Denny