how to tell gear ratio with out pulling cover/third member

[Blackjackbender]

im trying to figure what axle ratio i have in a nine inch i own. It has no tags and i do not want to remove the third member and count to find out if i do not have too. I read that you count the number of times the wheel/axle spins for the pinion to make one full spin and this tell you close to what gearing you have. I did this and i count about 4.5 rotations of the axle so this would lead me to believe it was 4.56 gearings? does this way of finding out gearing sound right? i was told the gearing was 3.00 by the orginal owner but im begining to think otherwise now and want to find out before i spend the money to regear the axle.


thanks

Ty

[fr3db3ar]

Sounds like you're right on....either 4.10 or 4.56 but actually you should be measuring how many times the ds turns per one revolution of the tire.

[Blackjackbender]

Originally Posted by fr3db3ar

Sounds like you're right on....either 4.10 or 4.56 but actually you should be measuring how many times the ds turns per one revolution of the tire.

well im watching the pinion yoke because its currently not in a vehicle

thanks.

this may be lower gearing then i wanted but should be fun

[fr3db3ar]

I understand you watching the yoke...I was commenting that you said you were turning the axle 4.5 times for 1 turn of the yoke

[brewmenn]

is it locked or open?

if it's locked and both sides turn together then just rotate the wheels one revolution and count how many time the pinion turns.

if it's open then you have to worry about what the other side is doing. If you hold one side still and turn the other side then you count the pinion rotations nad divide by 2.

[Blackjackbender]

Originally Posted by brewmenn

is it locked or open?

if it's locked and both sides turn together then just rotate the wheels one revolution and count how many time the pinion turns.

if it's open then you have to worry about what the other side is doing. If you hold one side still and turn the other side then you count the pinion rotations nad divide by 2.

well on axleshaft is pulled and the other is in. when they where both in when i spun on the other one spun too, so i assumed it had some sort of traction device in it.

god me worrying i only have 2.50's or similar now

[Blackjackbender]

anyone know the lowest possible gear ratio number in a ford nine inch? im tihnking 3.00 but not sure

[Roadhouse]

Originally Posted by Blackjackbender

anyone know the lowest possible gear ratio number in a ford nine inch? im tihnking 3.00 but not sure

you mean highest? if so it would be 2.86:1..........lowest would be 7.00:1

[swampjeep]

you need to put the other back in as Brewman said, and hold one while turning hte other, if they spin easily while holding one that is...

[TJrockdogg]

the technical way to do it would be to take the diff cover off and count the splines on the ring gear and pinion. divide the ring gear number by the pinion gear number. there is your answer. but locking one wheel and turning the other while counting revolutions of D-shaft would get you close.

[Haggar]

Yeah, but its a 3rd member style, so its a pain. Theres no cover, you ahve to pull the axle shafts, and unbolt the 3rd member which is messy.

[Yetti]

just so you have it under control. if you were to pull the third or the cover, there are numbers stamped on every set of gears , they look like 37-9. you divid the number so it comes out 4:11 so if you have to pull one apart then you can read the gear without guessing.

[Blackjackbender]

problem solved.


it was taken to Bill to get 3.80's and a auburn pro series diff.