axle gearing question

blackjackbender · Mar 20, 2006

m 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. was going to regear to 3.55 but if i have 4.56 in i will keep that for awhile for some fun and maybe switch it down the road.

thanks

Ty

LUCAFU1 · Mar 20, 2006

huh? i dont understand what you wrote.

spin the driveshaft as many times as it takes to make the tire turn 1 revolution. thats your gear. so if the d/s spun 4.5 times then yes you have 4.56s

blackjackbender · Mar 20, 2006

LUCAFU1 said:
huh? i dont understand what you wrote.

spin the driveshaft as many times as it takes to make the tire turn 1 revolution. thats your gear. so if the d/s spun 4.5 times then yes you have 4.56s

spin the driveshaft one turn and count how many times the axle shafts/tire spins during the full rotation.

pabear89 · Mar 20, 2006

blackjackbender said:
spin the driveshaft one turn and count how many times the axle shafts/tire spins during the full rotation.

....Make a mark at 12 oclock on the tire.

Make a mark at 6 oclock on the drive shaft.

Turn drive shaft counting complete turns needed to make the mark on the tire return to 12 oclock.

PB

LUCAFU1 · Mar 20, 2006

c'mon.

pabear89 is all over it.

WORTH · Mar 21, 2006

Are you guys trying to confuse him or help him?

marking the tires and shaft are the way to go, but you have to spin both tires 1 revolution unless you have posi.
and count the number of times the shaft spins.

It's easier with 2 people.

danny clemens · Mar 21, 2006

Or you could jack one side of the car off the ground if it is an open gear. Make sure you use jackstands though. Spin the yoke after marking and see how many times it takes to spin the tire or drum one time. If you have to spin the yoke 3 times while the tire turns 1 revolution you have 3:00 to 1 ratio. If the yoke turns 3 1/4 turns while the tire turns 1 you have a 3:25 to 1 ration. If the yoke spins 3 1/2 turn to the tires 1 turn you have a 3:50 to 1 ratio. Just keep counting the turns that the yoke turns with the tire turning 1 time. The number of turns your yoke turns will be your ratio to 1.

krash kendall · Mar 21, 2006

WORTH said:
Are you guys trying to confuse him or help him?

How about advanced math while cruising using RPM, MPH, and tire circumference?

blackjackbender · Mar 21, 2006

i forgot that rule only applies if its locked, so i actually have like 2.25 or so gears. im 90 percent sure the axle is open.

thanks for the help,

Ty

WORTH · Mar 21, 2006

krash kendall said:
How about advanced math while cruising using RPM, MPH, and tire circumference?

You forgot to take into account centrifical expansion at speed

danny clemens · Mar 21, 2006

blackjackbender said:
i forgot that rule only applies if its locked, so i actually have like 2.25 or so gears. im 90 percent sure the axle is open.

thanks for the help,

Ty

Are you sure it's not a 3.25 to 1. As far as I know Ford never put gears in Mustangs with gearing that high.

Edbert · Mar 22, 2006

2.70 and 2.80 were the standard base ratios for almost all classics. I have never heard of a lower one and cannot think of any reason a PO would hav made such a swap. The high performance gears that came as options were usually in the 3.25-3.89 range with options like the drag-pack being 4.11, I do not know if FoMoCo ever installed a 4.5x or bigger but I doubt it.

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