anyone know how to check the ratio of a rear axle w/o taking it apart

[1974ChevyC10]

someone has asked me if i would sell them the axle in my parts 74-i will on the condition its not like a 3.73 geared axle or something i may want in the future.so can anyone tell me how to check the ratio of an axle without taking it apart.

[Russell]

You can put the truck in neutral, and rotate the wheels seeing how many times the driveshaft turns for each wheel rotation...

Not sure about the ratios though, lol

[jimfulco]

Chock the front wheels so the truck won't roll. Put the trans in neutral. Make sure the parking brake is off. Jack up ONE rear wheel. Turn that wheel TWO full turns while counting the number of turns the driveshaft makes. The number of turns is your gear ratio.

Wheel wouldn't turn easily? You probably have a limited-slip (posi) rear end. In that case, jack up BOTH rear wheels, & turn them ONE full turn. Count driveshaft revolutions to get your ratio.

2-3/4 turns = 2.73
a little over 3 turns = 3.07 or 3.08
3-3/4 turns = 3.73
etc.

[1974ChevyC10]

i forgot to mention that the truck doesnt have a transmission in it so will it make any harder to check the rotations of the driveshaft-it does have the driveshaft in it just no trans.

[TIMSPEED]

If you know it's the original gears, then you can check the code. It's on the front of the passenger side axle tube, at about the 2'o'clock position, about 8" out from the pumpkin.

[jimfulco]

Probably best to disconnect the driveshaft so it doesn't flop around, or get somebody to hold it up for you.

[1974ChevyC10]

Originally Posted by jimfulco

Probably best to disconnect the driveshaft so it doesn't flop around, or get somebody to hold it up for you.

the truck has a 2 piece shaft will that make it any easier.

[ElGracho]

Why not just pull the cover and read the number of teeth off the ring gear? I know it's not what you wanted, but its the most surefire method to determine ratio and really isn't that big of a deal...

[1974ChevyC10]

Originally Posted by ElGracho

Why not just pull the cover and read the number of teeth off the ring gear? I know it's not what you wanted, but its the most surefire method to determine ratio and really isn't that big of a deal...

i dont have a problem with pulling off the diff cover but in order to get the accurate gear ratio its my understand you have to count both the number of teeth on the ring and pinion gear then divide the larger number by the smaller number-am i correct or way off base here and in order to get to the pinion gear dont you have to take the whole center section of the axle out?

[ElGracho]

Originally Posted by 1974ChevyC10

i dont have a problem with pulling off the diff cover but in order to get the accurate gear ratio its my understand you have to count both the number of teeth on the ring and pinion gear then divide the larger number by the smaller number-am i correct or way off base here and in order to get to the pinion gear dont you have to take the whole center section of the axle out?

Most ring gears will have the number of teeth on the ring gear and the pinion gear stamped on them. I've seen this on all of the 10 or so factory diffs I've seen apart. You see something like 41 10 or the corresponding numbers for your particular gears. Counting teeth shouldn't be necessary.

[1974ChevyC10]

Originally Posted by ElGracho

Most ring gears will have the number of teeth on the ring gear and the pinion gear stamped on them. I've seen this on all of the 10 or so factory diffs I've seen apart. You see something like 41 10 or the corresponding numbers for your particular gears. Counting teeth shouldn't be necessary.

i see-i was not aware of that information.thanks for the tip.now on my weekend ill get down to my dads shop and see what i got