460 Ford Forum banner

GEAR RATIO

2K views 3 replies 3 participants last post by  BadDadd 
#1 ·
Installed used 9 in.carrier. Tag was attached but doubting it's authenticity. Googled the tag info and came up with someone else having exact tag in another state and claiming carrier came out in 02 and from a completely different vehicle from what the local seller told me. Tag says 3.25. Need to clarify. Carrier is installed so counting teeth is not an option. Any tips tricks methods to get accurate ratio would be greatly appreciated.
 
#2 ·
i used to set up a lot of 9'' fords when i had more time 25 /30 years ago, i have plenty of the same tags in a box, that means nothing

In fact I use to look for H2J's all the time

You should of counted the gears,and did the math before you installed it
 
#3 ·
If You want to know your rear gear ratio or your rear end has no tag and you don't want to bust it open to count the Ring And Pinion Teeth, This is the method I use. This may not be Dead on Balls perfect If someone sucks at Math or Fractions, but it will get you in the ball park.

Simply put, A 3.25 ratio rear means Your drive shaft Will spin 3 and 25/100s (or 3 & 1/4 turns) revolutions to make your wheel/axle spin 1 complete revolution. The first digit of the ratio 3.25 translates to 3 Complete rotations of the pinion gear (then the decimal point .) and the last 2 digits .25 are fractions of (.100) and =s 1/4 of another rotation of the pinion gear that is required to make a complete rotation around the ring gear. Thus 3.25 .1 =s 3 and 1/4 rotations of the pinion to 1 rotation of the ring gear. You can apply this up to ANY rear end ratio, For example 3.00, 3.50, 3.90, 4.10 and so on.

To determine rear end ratio without busting open and counting gear teeth,

For a Limited Slip rear You hold (1) one of the wheels/axles stationary and do not let that one turn or move while you spin the drive shaft BY HAND and count the number of turns the drive shaft makes for the other (non stationary) wheel/axle to make a complete revolution.
For a Posi (full spool or mini spool) rear you do not hold 1 wheel back while doing the above. Otherwise, its the same procedure.
For a Locker setup, make sure axles are locked before you start counting the revolutions of driveshaft and the wheel/axle. Otherwise, its the same procedure.

For safety's sake Make sure your vehicle cannot roll away, rear end raised and rear tires off the ground, transmission in Neutral and the parking brake Released (not applied). I found it a good idea to use chalk or paint to make a mark on the drive shaft and wheel or hub to count from. This is easier for two people to perform this procedure but can be accomplished by only one.

Not trying to school anyone here, just thought it might be helpful for someone sometime in the future.
 
#4 ·
Thanks much, Raland. Bounced this project off of several people. Only info I got was inspection, spline count, and how to remove/replace. Not a word about ratio verification. Relieved to know it can still be done. Will try your method this weekend and see what I come up with.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top