Usually a whole number and decimal fraction, the drive-axle ratio is a comparison of the number of gear teeth on the ring gear of the rear axle and the pinion gear on the driveshaft. For example, a 4.11:1 ratio means there are 4.11 teeth on the axle’s ring gear for each tooth on the driveshaft’s pinion gear.

The choice of a numerically higher axle ratio will only knock off about 1 mile per gallon from the truck’s fuel economy. But if you do a lot of high-speed driving, you might want to consider a vehicle with a numerically lower gear set to decrease engine rpm and improve fuel economy.

Vehicle Description Section The fourth through eighth digits describe your vehicle’s model, body type, restraint system, transmission type, and engine code. The ninth digit is the check digit, which is used to detect fraudulent VINs.

All Chevrolet rear ends can be identified by comparing the gasket shape to an identification chart similar to the one found on Drivetrain’s differential identification page (see References). A visual chart of different GM/Chevrolet rear ends is found on Ring & Pinion’s differential types web page (see References).

about 450 HP

Weak pinion gears. The 7.5 can take about 250 hp with a auto trans and last a good long time.

When looking at the housing from the rear, an 8.5 will have two squared off chunks of casting hanging on each side near the bottom of the differential. An 8.2 (shown) will have the same contour as the cover. Most 8.2 factory covers also have the strange protrusion at the top.

Buick and Oldsmobile axles can be identified by their code, usually found on the right rear side of the differential carrier or on the passenger side axle tube. The axle code, if on the differential, is comprised of one or two letters for 1964-’70 models, followed by a three-digit build date.

Information about Differentials in GM vehicles can usually be obtained by looking at the RPO or “Regular Production Option” codes contained in the Service Parts Identification tag in the glovebox. Whenever possible, reference the tag numbers when ordering parts for your Differential.

450

Chances are your truck has a 12-bolt rearend, but if not, it’s fairly easy to get your hands on one. Not only are they common, but they can also be pretty solid when built correctly. In fact, they can stand up to around 800 hp, which is perfect for a street truck with some performance mods under the hood.

Even though it has been used in every major GM rear-wheel-drive platform, the 10-bolt has a bad reputation for being a low-performance unit. Nothing could be further from the truth. The 10-bolt can handle just about anything you throw at it, as long as you use the right axle, either the 8.5- or 8.6-inch.

A stock WS6 puts out 345 ft lbs of torque (And a theoretically under rated 320hp). That’s about all the 10 bolt can *reliably* handle with the stock tires and a stick shift. I’m on my 3rd unit with a mostly stock motor, good suspension, and sticky but street legal road race tires.

Dead stock (31 spline version, which is what the Explorer has) it can handle up to about 400 rwhp as long as you’re not on DR’s or Slicks. As soon as you go to those, you have to weld the tubes at a minimum.

Sure a 9 inch can handle 400+ horse in a car. But there is alot less weight on the axle. And drag cars, and circle track cars are not running agressive tires that are 35 inches tall or bigger. So you can feed more horsepower to an axle in a car, and still have it hold up.

Ford 9″