How do I identify a Chevy 12 bolt rear end?

How do I identify a GM 12-bolt rear end?

The easiest way to identify a 12-bolt rearend is obviously by the 12 bolts holding the rear cover onto the axle housing. The pinion shaft on passenger-car differentials is 1-5/8-inch in diameter and the cover is oval, measuring 10-15/16-inches wide by 10-5/8-inches tall.

How do I identify a Chevy 12-bolt?

12-bolt axles can be identified by casting numbers on the bottom of the cast-iron center-section and on the front of the passenger side axle tube. This identifies the car make and model, gear ratio, date of casting and assembly and factory of origin.

Where are the numbers on a 12-bolt rear end?

12-Bolt Housings by the Numbers

The casting numbers for the 12-bolt housings are typically found on the upper rear of the driver’s side of the center section. The casting numbers are simple to decode.

Are all GM 12-bolt rear ends the same?

They are not interchangeable. That doesn’t mean the truck rearend is not capable of receiving performance upgrades. To the contrary, aftermarket 30-spline differentials and axles are available. GM car and truck 12-bolt rearends are easily distinguishable by the cover shape.

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How do I identify my Chevy truck rear end?

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).

How do I know if my rear end is Positraction?

If you can turn the wheel on your side while the other wheel is held still, the rear differential is not a Positraction unit. If you cannot turn the wheel on your side while the other person is holding their wheel in place, then the axle is a Positraction.

What size is a GM 12 bolt rear end?

12-Bolts to Glory The GM 12-bolt debuted in 1965 and was mass-produced until 1972. It features an 8.875-inch ring-gear carrier held in place with two internal main caps. The pinion gearshaft measures 1.625 inches in diameter and is shimmed to achieve the proper pinion depth.

How do I tell what gear ratio my Vin is?

Identify the VDS section, the fourth through eighth digits of the VIN. This section typically includes information such as the vehicle model, engine size and body type. While not every vehicle manufacturer includes gearbox ratio information in the VDS, this will be where the information is found if it was included.

What gear ratio is a 12 bolt Chevy rear end? GM Chevy 8.875″ 12-Bolt CAR Rearend Posi, Gear, Bearing Kit Package – 3.42 Ratio : Automotive.

How do I identify my GM rear differential?

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.

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How can you tell if a 12 bolt is posi?

If you see springs in the window of the carrier, either coil springs like this or an S-shaped spring, it’s a Posi unit. 2 First order of business is to pull the spider gear pinion shaft’s bolt. Don’t break it.

How can you tell the difference between an 8.2 and 8.5 rear end?

Another way to tell the difference between an 8.2 and an 8.5 rearend is to pull the cover and look at the bolt holding the spider gear crosspin. If it takes a 1/2-inch wrench to remove it, it’s an 8.2. If it takes a 5/16-inch wrench to remove it, it’s an 8.5.