Were do you find what gear ratio on rear ends do i count the teeth in ring gear? its a1979 cj7

Should be a tag on the differential under one of the cover bolts that has that info on it. Otherwise you will have to take cover off and the ring gear will have the ration stamped on it on the edge... You could also count the teeth on the ring and pinion, divide the ring gear count by the pinion gear count.

NO--- Check Gear Ratio On Tag Or Tube--Front and Rear Are Not The Same. Or Count Teeth On Pinion And Ring Gear--Divide Pinion Number Into Ring Gear Number For Ratio.

You will need to locate the tag on the rear end cover and find out the gear ratio, if theres no tag then you will need the manufactors date on the door, for example 04/05, and also if it got abs, there are three types,4.10 or 3.55 or 3.73. the best way is the tag or pull cover and count the teeth on ring gear and pinion gear and divide the two to get the ratio. goodday, also try to call the dealer parts dept and give them the vin # and they may be able to tell you the type rear end you have,

Should be a metal tab bolted to rear inspection cover of differential displaying gear ratio or count the number of teeth on pinion (small gear connected to drive shaft) Divide number into the number of teeth on ring gear

If you take the VIN # to a GM dealer they should be able to tell you the original rear end that the vehicle came with. If you are going to take the rear end to a shop they will be able to tell when they take it apart. If it is a posi rear end it will have a tag under one af the cover bolts (if it has not been removed) Once inside a posi rear end is immediately identifiable from the clutch pack. Also the number of teeth is stamped on each (pinion and ring) gear. Divide ring gear # by Pinion gear # to get rear end ratio. Didn't get directly to your question, but I hope this helps. Let me know. Thanks

I will assume you are missing your id tag. You will need to remove the rear cover and count the teeth. If you have never opened a drive axle I will warn you it will most certainly stink.

Now to figure the gear ratio:

The best way is to count the teeth on the ring gear and divide by the number of teeth on the pinion gear. Or you can count the number of turns of the pinion it takes to get one full turn of the ring gear.


For example, if we divide a ring gear with 41 teeth by a pinion gear with 10 teeth we find that the gear ratio is 4.10:1 (41/10 = 4.10).

It will be the same as the rear. It the rear is missing you will need to count the ring and pinion teeth. Ring gear teeth Divided by Pinion gear teeth.

If you just want a ballpark idea, you can rotate the driveshaft and count how many revolutions it takes to make the tire go around once. That will be your ratio.

you can count the teeth on the ring gear and divide that # by the tooth count on the pinion. An example is: ring gear 100, pinion 10 ...100divided by 10 is 10, expressed as 10 to one. (fake #) your diff is likely a 3 series such as 3.23 to 1. or a four series such as 4.11 to 1. If you have four wheel drive it is critical to match exactly. if not you can get better performance by changing ratio to something that better fits your needs. 4 series pull loads well, 3 series are better on fuel.(depending upon terrain)

Yuo deifinitely have to get rid of one differential to match the other. I would change the rear diff as the gearing in that one will give you really poor mileage... additionally welded spider gears (poor mans positraction) make cornering a nightmare (the outside wheel must turn faster than the inner one on turns, which is why no one uses "spool" type differentials on anything but drag race vehicles (because they only go in straight lines).
As far as which Dana unit you are supposed to have, YOU MUST MATCH THE EXACT GEAR RATIO TO THE FRONT UNIT or, it will destroy the transfer case!!! You could even modify a chevy or ford diff to fit under there, but the ratio match has to be exact!!! To find ratio, count the ring gear teeth and the pinion gear teeth. I don't remember the formula but you need to establish a ratio from these two #s.(divide the ring gear# by the pinion#??? answer is expressed as (answer:1 such as 3.23:1))

The C/Tr: C refers to the colour of the vehicle Tr refers to the interior colour A/TM is your transmission type. None of those numbers identify the rear end ratio.

What you need to do: Since you have to replace the rear end, yank it out. Examine the ring & pinion gears on the differential carrier. Mark on each a starting point, and count the teeth on both the ring & pinion gears. Now, after you have both totals of teeth, divide the # of teeth on the pinion by the number of teeth on the ring gear. Example: 12 teeth on the pinion, 46 teeth on the ring
12/46 = 3.83 ratio