NOS 4.33 gearset O 12 bolt Original Box!
Thread Starter
Registered User
Joined: May 2006
Posts: 1,142
From: Bartlesville, Oklahoma
John, these are factory gears so they fit the 588 and 672 carriers.
673_____1967-1970_____2.56-2.78____28 spline axles
671_____1967-1970_____3.08-3.23____28 spline axles
588_____1967-1970_____3.42-5.00____28 spline axles
672_____1967-1968_____3.42-5.00____31 spline axles
673_____1967-1970_____2.56-2.78____28 spline axles
671_____1967-1970_____3.08-3.23____28 spline axles
588_____1967-1970_____3.42-5.00____28 spline axles
672_____1967-1968_____3.42-5.00____31 spline axles
Last edited by orange442; Jun 28, 2014 at 11:57 AM.
Registered User
Joined: Dec 2011
Posts: 7,286
Hearsay in my PN database:
The 12 bolt O axle was used under most 1967-1970 Cutlass, 4-4-2, Hurst/Olds and Vista Cruisers. The housing cover can be identified from the pictures below. Internally, the O axle features an 8.5" ring gear. Which is attached to the carrier by 10 bolts (this 8.5" 10 bolt ring gear is not the same as the 1971 and newer 10 bolts). All use 28 spline axle shafts except the 1967-1968 models originally equipped with 3.42 thru 5.00 gears. These use 31 spline axles.
The 31 spline models also use larger carrier bearings than the 28 spline models. Consequently, the 31 spline carriers cannot be used in a housing originally equipped with 28 spline axles, and vise-versa.
1967-1969 axle bearings are a sealed ball bearing design. 1970's axle bearings are an open roller design lubricated by the differential oil. All O axle shafts are retained by a four bolt flange (not internal C-clips). Three different carriers were used depending on ratio: 2.56-2.78, 3.08-3.23 and 3.42 thru 5.00. These have different pinion centerline to ring gear mounting flange offsets (The 28 spline and 31 spline carriers feature the same mounting flange offset). All O axles use a 1.626" diameter, 27 spline pinion stem. All Anti-Spin models (Oldsmospeak for "posi") are clutch type differentials. Which utilize an "S" shaped spring to provide pressure against the clutch packs.
The 12 bolt O axle was used under most 1967-1970 Cutlass, 4-4-2, Hurst/Olds and Vista Cruisers. The housing cover can be identified from the pictures below. Internally, the O axle features an 8.5" ring gear. Which is attached to the carrier by 10 bolts (this 8.5" 10 bolt ring gear is not the same as the 1971 and newer 10 bolts). All use 28 spline axle shafts except the 1967-1968 models originally equipped with 3.42 thru 5.00 gears. These use 31 spline axles.
The 31 spline models also use larger carrier bearings than the 28 spline models. Consequently, the 31 spline carriers cannot be used in a housing originally equipped with 28 spline axles, and vise-versa.
1967-1969 axle bearings are a sealed ball bearing design. 1970's axle bearings are an open roller design lubricated by the differential oil. All O axle shafts are retained by a four bolt flange (not internal C-clips). Three different carriers were used depending on ratio: 2.56-2.78, 3.08-3.23 and 3.42 thru 5.00. These have different pinion centerline to ring gear mounting flange offsets (The 28 spline and 31 spline carriers feature the same mounting flange offset). All O axles use a 1.626" diameter, 27 spline pinion stem. All Anti-Spin models (Oldsmospeak for "posi") are clutch type differentials. Which utilize an "S" shaped spring to provide pressure against the clutch packs.
Registered User
Joined: May 2011
Posts: 3,688
From: Delta BC Canada
Type O
Hearsay in my PN database:
The 12 bolt O axle was used under most 1967-1970 Cutlass, 4-4-2, Hurst/Olds and Vista Cruisers. The housing cover can be identified from the pictures below. Internally, the O axle features an 8.5" ring gear. Which is attached to the carrier by 10 bolts (this 8.5" 10 bolt ring gear is not the same as the 1971 and newer 10 bolts). All use 28 spline axle shafts except the 1967-1968 models originally equipped with 3.42 thru 5.00 gears. These use 31 spline axles.
The 31 spline models also use larger carrier bearings than the 28 spline models. Consequently, the 31 spline carriers cannot be used in a housing originally equipped with 28 spline axles, and vise-versa.
1967-1969 axle bearings are a sealed ball bearing design. 1970's axle bearings are an open roller design lubricated by the differential oil. All O axle shafts are retained by a four bolt flange (not internal C-clips). Three different carriers were used depending on ratio: 2.56-2.78, 3.08-3.23 and 3.42 thru 5.00. These have different pinion centerline to ring gear mounting flange offsets (The 28 spline and 31 spline carriers feature the same mounting flange offset). All O axles use a 1.626" diameter, 27 spline pinion stem. All Anti-Spin models (Oldsmospeak for "posi") are clutch type differentials. Which utilize an "S" shaped spring to provide pressure against the clutch packs.
The 12 bolt O axle was used under most 1967-1970 Cutlass, 4-4-2, Hurst/Olds and Vista Cruisers. The housing cover can be identified from the pictures below. Internally, the O axle features an 8.5" ring gear. Which is attached to the carrier by 10 bolts (this 8.5" 10 bolt ring gear is not the same as the 1971 and newer 10 bolts). All use 28 spline axle shafts except the 1967-1968 models originally equipped with 3.42 thru 5.00 gears. These use 31 spline axles.
The 31 spline models also use larger carrier bearings than the 28 spline models. Consequently, the 31 spline carriers cannot be used in a housing originally equipped with 28 spline axles, and vise-versa.
1967-1969 axle bearings are a sealed ball bearing design. 1970's axle bearings are an open roller design lubricated by the differential oil. All O axle shafts are retained by a four bolt flange (not internal C-clips). Three different carriers were used depending on ratio: 2.56-2.78, 3.08-3.23 and 3.42 thru 5.00. These have different pinion centerline to ring gear mounting flange offsets (The 28 spline and 31 spline carriers feature the same mounting flange offset). All O axles use a 1.626" diameter, 27 spline pinion stem. All Anti-Spin models (Oldsmospeak for "posi") are clutch type differentials. Which utilize an "S" shaped spring to provide pressure against the clutch packs.
A superb & thorough summary of the Type O differential. Thanks!
