Gear Ratio

I'm changing the rear diff fluid on my 62 cj5. The tag says 5:38, but the gears inside have 4:75 scribed on them. What gives?

 

start counting teeth..

 

Keep spinning. The ratio is usually stamped, not engraved. That could be a date or some sort of production code.

Like jeepenstein said, start counting to know for sure.

The other numbers on that little tag: 43-8
That means there are 43 teeth on your ring gear and 8 teeth on the pinion. Divide them together and your answer is 5.375, rounded up to 5.38.

 

My 70 cj5 has 538 gears and it's slow. It has a t98. This jeep has a t90 and likely the same gearing. Its just so much quicker than mine. Must be the transmission and smaller tires I'm thinking?

 

The engraved numbers are the part number match with the pinion gear. Once honed to each other they are given a hand engraved number so that anyone assembling it will know they are a matched pair. As stated above gear ratio numbers will be factory stamped into the gear. Not put on with a vibrator pencil.

 

Not a factory gear set...
count the teeth as mentioned

 

My 65 with a T90c and 4.27s felt way better than my 57 with 5.38 and T90a.

My 65 motor is much healthier too. Could be that as well. More recent tune up and better spark, cleaner carb, etc.

Def count teeth.

 

How does your 70 feel starting in 2nd?

 

I start in 2nd all the time (unless on a steep grade) 4.88’s with the T-86 and Dauntless v6.
Pulls quick and hard, surprises a lot of people when the light turns green.