Isuzu OEM 5.12:1 Ring & Pinioin Gears....

[BigSwede]

The short answer is those numbers represent the number of times the driveshaft will turn relative to one turn of the axle and wheel, due to the reduction gearing in the differential.

Putting a numerically larger gear ratio in the differential compensates for putting larger tires on the vehicle, because the larger tires effectively lower the final drive ratio. A simple percentage calculation is all that is needed to find your desired gearing.

In this case:

Desired 35" tires minus stock 29.5" size = 5.5

5.5 divided by stock 29.5" size = .186, or an 18.6% difference in tire size from stock.

Now for the gearing:

5.12 gears minus stock 4.30 = 0.82

0.82 divided by stock 4.3 = 0.19, or a 19% difference from stock gearing to the 5.12 size.

So the 5.12 gears with 35" tires are very close to the same drive ratio as stock 4.30 gears and 29.5" tires. Meaning that your vehicle's git-up-and-go will be about the same.

[BigMeatVX]

Received my REAR 5.12 gears the other day...for the isuzu 12 bolt ...

However, These gears are 244mm and are made to fit the Trooper 12bolt.
To use them in a VX you will need the axle shafts and 3rd member out of a 98+ Trooper...
It seems isuzu discontinued the smaller 12 bolt (VX style) and all the later ones are the bigger stronger "modified" 12 bolt....the axle shafts are Dana 60 sized and the ring gear is larger also....ARB is availble with these.

I will be installing them very soon...