For the best rebuilt GM axles, contact Houston Rebuilt Axles and see how much we can save you on an axle rebuild. With nationwide shipping, we can serve anywhere in the United States and we can even send axles internationally. We can find an axle for you and ship it to you. Let us know what you need. Alternatively, we can find you a GM axle and/or differential if you don’t have one to rebuild. We also provide advice on choosing a suitable GM axle for your application. If you are unsure about what axle you need or what axle you have, here is information on the various GM axles to help you identify it and its internals.
GM Axles
GM axles refers to Chevrolet, GMC, Oldsmobile and Pontiac axles at various times throughout history. GM differentials are generally divided into two types, the 10-Bolt and the 12-Bolt and have been used on GM passenger cars, muscle cars and trucks for decades. The Chevy 12-bolt differential was introduced in 1965 and has been the preferred performance differential over the 10-bolt due to the 10-bolt undeservedly gaining a reputation as a weak differential. The truth is that there are many variants of the 10-bolt, many of which are very strong, and capable of transmitting up to 1000hp in stock form. The stronger variants of the 10-bolt differentials include the 8.5 and 8.6-inch (ring gear diameter) units. The reason for their added durability is due to their larger ring and pinion gear surface. The other variants of the 10-Bolt are the axles that earned the weak differential reputation. To help you identify the different units, here is how you can identify each type of GM Differential:
How to Identify the various 10-Bolt GM Differentials
Nomenclature for the axle refers to the number of ring gear bolts and the axle cover has 10-bolts as the name suggests.
8.2” Differential
The lower case of the 8.2 axle housing is smooth and round and the differential cover is 11 inches with a diagonal indentation at the top or a 10 and ⅝” irregularly shaped cover. A stock differential will have a pinion nut measuring 1 and ⅛”. The ring gear bolts have 9/16 socket heads and the pinion diameter is 1.438”, 25 spline axles that use C-clips on the inner ends of the axle shafts.
8.2” 10-Bolt axles were commonly used in Chevy, Buick and Oldsmobile A-Body 1964-1972, Chevy B-Body 1964-1972, Chevy and Pontiac F-Body 1967-1970, Chevy X-Body 1964-1971.
8.5” Differential
The 8.5” 10 bolts have two lugs on the housing at the 5 and 7 o’clock position, an 11-inch housing cover, 3 and ¾ inch spacing between the lower cover bolt and either adjacent bolt. It has a bulge on the driver’s side or a 10 and ⅝ inch irregular shape with the bulge. On a stock axle, the pinion nut is 1 and ¼ inches. It uses 7/16 20 inch (reverse or) left-hand thread bolts holding the ring gear to the carrier. The pinion shaft has a 1.625” diameter with 28 or 30 splines. Like the 8.2”, the axle shafts are held in using c-clip retainers.
8.5” 10-Bolt were commonly applied to Chevy, Buick and Oldsmobile A-Body 1970-1977, Chevrolet B-Body 1970-1996, Buick E-Body 1975-1978, Chevrolet and Pontiac F-Body 1970-1981, Chevrolet and Oldsmobile X-Body 1970-1979 and various trucks and vans from 1979-2008.
7.5” & 7.625” Differentials
The housing on these differentials are very similar to the 8.5” differential housing where it has 2 lugs at the 5 and 7 o’clock position, however, the lugs are smaller and the oval shaped cover measures 8 and 5/16 inches by 10 and 9/16 inches. The distance between the lower center cover bolts and the adjacent ones is 3 and ¼ inches. Internally, the pinion shaft measures 1.438 inches.
The 7.5” & 7.6” 10-Bolt differentials were commonly applied to Chevy and Oldsmobile B-Body, 1978 -1996, Chevrolet and Pontiac F-Body 1981 – 2002, Chevy, Oldsmobile, Buick G-Body 1977-1988, Chevrolet H-Body 1975+, various trucks and SUV S-Series 1982-2005 and various GM mini-vans, Astro, Safari etc 1982-2005.
10-Bolt Axle Gear Codes
| Axle Ratio | Ring Gear Tooth Count | Pinion Gear Tooth Count |
| 2.56:1 | 41 | 16 |
| 2.73:1 | 41 | 15 |
| 3.07:1 | 43 | 14 |
| 3.08:1 | 40 | 13 |
| 3.08:1 | 37 | 12 |
| 3.31:1 | 43 | 13 |
| 3.36:1 | 37 | 11 |
| 3.42:1 | 41 | 12 |
| 3.55:1 | 39 | 11 |
| 3.73:1 | 41 | 11 |
| 4.10:1 | 41 | 10 |
| 4.11:1 | 37 | 9 |
Axle Label 10-Bolt Axle Carrier Codes
| Axle | Series | ID Code | Gear Ratio |
| 8.2″ | 2-Series | ED32118 | 2.73:1 & Lower |
| 8.2″ | 3-Series | EDB30116 | 3.08:1 & Higher |
| 8.5″ | 2-Series | 410409N | 2.56:1 & Lower |
| 8.5″ | 3-Series | 410408N | 2.73:1 & higher |
How to Identify the various 12-Bolt GM Differentials
Unlike 10-bolt axle assemblies, the 12-bolt axle assemblies have different components installed in car axles than in truck axles. In order to differentiate the two, here are some distinguishing factors:
The car variant of the 12-bolt axle has an oval shaped differential cover measuring 10 and 15/16 x 10 and ⅝ inches. Trucks have a smaller inner pinion shaft measuring 1.438 versus 1.675 in cars. The truck 12-bolt has an irregular shape, early truck 12-bolts had 12 large axle splines and the differential carrier is narrower than on the passenger cars. Although the truck axles are more plentiful, due to the lesser number of splines, the truck axles were not as strong as the passenger car axle but aftermarket parts are available to upgrade the number of splines to improve the strength. The truck and car axles are not interchangeable due to the various differences.
12-Bolt axles were commonly used in Chevrolet, Oldsmobile and Pontiac A-Body 1964-1972, Chevrolet B-Body 1964-1972, Chevrolet, Pontiac F-Body 1967-1972, Chevrolet X-Body 1964-1972.
12-Bolt Differential Carriers
The 12-Bolt carriers use the same series types as the 10-Bolt; Series 2, 3 and 4 with the most common being the 2-series.
12-Bolt Housing Numbers
The axle housing usually has the casting numbers on the upper rear driver’s side center section. The casting numbers show the build date. The axle ratio codes are as follows:
12-Bolt Axle Ratio Code Chart
| Axle Code | Axle Ratio | Axle Code | Axle Ratio | Axle Code | Axle Ratio |
| CA | 3.08 | CY | 3.07 | K7 | 4.56 |
| CB | 3.36 | CZ | 2.73 | K8 | 4.88 |
| CC | 3.73 | FH | 2.73 | KA | 3.55 |
| CD | 3.07 | FI | 2.73 | KB | 3.55 |
| CE | 3.08 | FJ | 3.08 | KC | 2.73 |
| CF | 3.31 | FK | 3.08 | KD | 2.73 |
| CG | 3.36 | FL | 3.36 | KF | 3.55 |
| CH | 2.73 | FM | 3.36 | KJ | 3.55 |
| CI | 3.73 | FN | 3.55 | KK | 4.1 |
| CJ | 3.08 | FO | 3.55 | KM | 4.56 |
| CP | 2.73 | FP | 3.7 | KO | 4.88 |
| CR | 3.7 | K2 | 3.55 | KW | 2.73 |
| CU | 3.73 | K3 | 3.55 | KX | 3.07 |
| CV | 3.7 | K4 | 3.73 | KY | 3.31 |
| CW | 3.31 | K5 | 3.73 | KZ | 3.31 |
| CX | 3.07 | K6 | 4.1 |
GM Differential Specifications Chart
GM 7.2” Independent Front Suspension
- Ring Gear Diameter 7.2”
- Pinion Diameter 1.315”
- 27 Spline
- Ring Gear Bolts 10mm x 1.25
- Carrier Breaks 3.08 / 3.23
GM 7.5” & 7.625”
- Ring Gear Diameter 7.5”
- Pinion Diameter 1.438”
- 27 Spline
- Ring Gear Bolts 7/16” 20LH
- Cover Bolts 10
- Carrier Breaks 3.08 / 3.23
GM 7.6” Independent Front Suspension
- Ring Gear Diameter 7.625”
- Pinion Diameter 1.438”
- 28 Spline
- Ring Gear Bolts 7/16” 20RH
- Cover Bolts 10
- Carrier Breaks 3.08 / 3.23
GM 7.6” Independent Rear Suspension
- Ring Gear Diameter 7.6”
- Pinion Diameter 1.438”
- 27 Spline
- Ring Gear Bolts 7/16” 20RH
- Cover Bolts 10
GM 7.75”
- Ring Gear Diameter 7.75”
- 27 Spline
- Ring Gear Bolts 8
- Cover Bolts 9
- Carrier Breaks 2.77 / 3.27
GM 8.0” Rear
- Ring Gear Diameter 8”
- Pinion Diameter 1.781”
- 27 Spline
- Ring Gear Bolts 7/16” 20LH
- Cover Bolts 10
GM 8.2”
- Ring Gear Diameter 8.20”
- Pinion Diameter 1.438”
- 17 Spline
- Ring Gear Bolts 7/16” 20RH
- Carrier Breaks 3.7 / 4.11
GM 9.375”
- Ring Gear Diameter 9.375”
- Pinion Diameter 1.438”
- 17 Spline
- Ring Gear Bolts 3/8” 24RH
- Cover Bolts 12
GM 8.2”
- Ring Gear Diameter 8.20”
- Pinion Diameter 1.438”
- 25 Spline
- Ring Gear Bolts 3/8” 24LH
- Cover Bolts 10
- Carrier Breaks 2.76 / 3.07
GM 8.2” Bolt-in
- Ring Gear Diameter 8.20”
- Pinion Diameter 1.438”
- 27 Spline
- Ring Gear Bolts 3/8” 24LH
- Cover Bolts 10
- Carrier Breaks 3.23 / 3.36
GM 8.25” Independent Front Suspension
- Ring Gear Diameter 8.25”
- Pinion Diameter 1.625”
- 30 Spline
- Ring Gear Bolts 7/16” 20LH
- Carrier Breaks 3.23 / 3.42
GM 8.5” (C-Clip, 10 Bolt Cover)
- Ring Gear Diameter 8.5”
- Pinion Diameter 1.625”
- 30 Spline
- Ring Gear Bolts 7/16” 20LH
- Cover Bolts 10
- Carrier Breaks 2.56 / 2.73
GM 8.5” (12 Bolt Cover)
- Ring Gear Diameter 8.20”
- Pinion Diameter 1.438”
- 27 Spline
- Ring Gear Bolts 3/8” 24LH
- Cover Bolts 10
- Carrier Breaks 3.23 / 3.36
GM 8.6”
- Ring Gear Diameter 8.6”
- Pinion Diameter 1.625”
- 30 Spline
- Ring Gear Bolts 7/16” 20LH
- Cover Bolts 10
- Carrier Breaks 2.56 / 2.73
GM 8.6” Independent rear suspension
- Ring Gear Diameter 8.6”
- Pinion Diameter 1.875”
- 32 Spline
- Ring Gear Bolts 7/16” 20LH
- Cover Bolts 10
GM 8.875” (Car 12 Bolt)
- Ring Gear Diameter 8.875”
- Pinion Diameter 1.625”
- 30 Spline
- Ring Gear Bolts 3/8” 24RH
- Cover Bolts 12
- Carrier Breaks 2.76 / 3.08 – 3.90 / 4.10
GM 8.875” (Truck 12 Bolt)
- Ring Gear Diameter 8.875”
- Pinion Diameter 1.438”
- 30 Spline
- Ring Gear Bolts 3/8” 24RH
- Cover Bolts 12
- Carrier Breaks 2.76 / 2.76 – 3.42 / 3.73
GM 9.25” Independent Front Suspension
- Ring Gear Diameter 9.25”
- Pinion Diameter 1.875”
- 30 Spline
- Ring Gear Bolts 12mm 1.5LH
GM 9.25” Independent Front Suspension
- Ring Gear Diameter 9.25”
- Pinion Diameter 1.875”
- 30 Spline
- Ring Gear Bolts 12mm 1.5LH
- Cover Bolts 12
GM 9.5”
- Ring Gear Diameter 9.5”
- Pinion Diameter 1.875”
- 30 Spline
- Ring Gear Bolts 12mm 1.5LH
- Cover Bolts 14
GM 10.5”
- Ring Gear Diameter 10.5”
- Pinion Diameter 1.875”
- 30 Spline
- Ring Gear Bolts 12mm 1.5LH
- Cover Bolts 14
GM 11.5” Independent Front Suspension
- Ring Gear Diameter 11.5”
- Pinion Diameter 2”
- 30 Spline
- Ring Gear Bolts 9/16” 18RH
- Cover Bolts 14
- Carrier Breaks 4.10 / 4.63
For GM Bill of Material information, see our GM Axles BOM information page.