69HEMICORONETR/TCONV
Well-Known Member
Chrysler 8 3/4" Rear Axle & Swap Information
Chrysler Corporation's 8.75" rear axle assembly first appeared in 1957. The measurement refers to the 8-3/4" diameter ring gear. This gear, which is turned by the pinion gear, changes the direction of the power being transmitted to it. The pinion gear is turned by the driveshaft. It is a banjo-type (Hotchkiss) axle. The term "banjo" means that the differential is contained in a removable carrier (or center section) assembly. When the carrier is removed, the empty housing resembles a banjo. The carrier is removed from the front of the housing, and is retained by 10 nuts on studs in the housing. The rear of the housing is smooth with a non-removable rear cover that is welded onto the main housing. The housing and axle tubes are made from stamped and welded steel.
The 8-3/4" axle was the primary axle assembly used in most non-compact car lines through 1972. It was also used in some high performance compact cars. Of the many axle types that Chrysler used since 1960, it was also the only axle assembly developed by Chrysler. It was phased out because it was more expensive to manufacture than using the outsourced Spicer 7.25", 8.25" and 9.25" units.
There are three basic types of 8.75" carriers available, which are distinguished by their drive pinion stem diameter. The choice of axle pinion assembly was determined based on a combination of vehicle horsepower and weight. Below are the 8.75" axle carrier types.
8.75" Axle Carrier Types and Years of Production
* ''741' Casting - 1 3/8" (1.375") Small Stem Pinion.
Carrier casting numbers were 1820657 (1957-1964) and 2070741 (1964-1972). This unit was usually used in low weight/medium horsepower and high weight/low horsepower applications. Although it is the weakest of the 8.75" units, it is still a stout unit, and is stronger than the Spicer-built Chrysler 8.25" rear. The 1 3/8" pinion is also larger than the pinion in the Ford 9" rear.
* ''742' Casting - 1 3/4" (1.75") Large Stem Pinion.Carrier casting numbers were 1634985 (1957-1964) and 2070742 (~1961-1969). This assembly was replaced by a phase-in of the 1-7/8" pinion '489' casting starting in the 1969 model year. This assembly was typically used in high weight/medium horsepower applications through high weight/high horsepower applications. Although not generally considered to be stronger then the '489' carrier, the '742' carrier is extremely stout, and is favored by many Mopar enthusiasts because they are easier to set up. Noted Mopar enthusiast John Kunkel mentioned that the biggest advantage of the 742 carrier is that it has the largest rear pinion bearing of all the 8 3/4" carriers. The larger bearing helps to prevent pinion deflection better under a load than the others. It also has a larger pinion than the Ford 9" rear.
* '489' Casting - 1-7/8" (1.875") Tapered Stem Pinion Carrier casting numbers were 2881488 or 2881489 (1969-1974). This assembly was introduced in 1969 and was phased-in to replace the 1-3/4" pinion '742' unit through 1970. Note: the 1-3/4" pinion also appeared in some '489' carriers during this period. By 1973, the '489' was the only unit available in passenger car applications, and was typically used in high weight/medium horsepower applications through high weight/high horsepower applications. This carrier is considered to be the strongest by some Mopar enthusiasts. Because it requires a crush sleeve to set bearing preload, some Mopar enthusiasts prefer the '742' casting. This is not really an issue now because there are now parts available to eliminate the crush sleeve. The '489' and the whole 8 3/4 unit in general is highly under rated I would put one up against a Ford 9" inch any day, I raced them for years with Monster Torque 440s and HEMIs coupled to them, and I never broke a rear, but I have wrung two drive shafts into.:grin:
Carrier Identification:
All 8-3/4" carrier assemblies can be identified externally by the casting numbers. The casting numbers are cast onto an ID pad on the driver's side of the carrier just behind the 'snout' of the case where the yoke attaches to the pinion. In addition to the casting numbers:
* The '741' will usually have a large 'X' cast on the left side
* The '742' will usually have a large '2' cast on the left side
* The '489' will have a large '9' cast on the left side.
Gear Ratio and Sure-Grip Identification:
Through 1965, the factory ratio was stamped on the identification boss, followed by an 'S' if it had a Sure Grip. After 1965, a tag was affixed under one of the carrier mounting nuts to identify the ratio. If it had a Sure Grip, an additional Sure Grip lube tag was sometimes added. Later year versions sometimes had the filler plug painted orange.
Gear Selection:
Because of its popularity, a wide range of gear selections is available for the 8.75" unit. Gear ratios available on the 8-3/4" axle through the years include, but are not limited to: 2.76, 2.93, 3.23, 3.31, 3.55, 3.73, 3.91, 4.10, 4.56, 4.89, 5.17 and 5.57.
Interchange Notes:
Any complete 8.75" carrier will interchange with another 8.75" carrier in any 8.75" housing. The Sure-Grip assemblies also interchange. However, none of the other separate parts such as cases, pinions and bearings will interchange.
Chrysler Corporation's 8.75" rear axle assembly first appeared in 1957. The measurement refers to the 8-3/4" diameter ring gear. This gear, which is turned by the pinion gear, changes the direction of the power being transmitted to it. The pinion gear is turned by the driveshaft. It is a banjo-type (Hotchkiss) axle. The term "banjo" means that the differential is contained in a removable carrier (or center section) assembly. When the carrier is removed, the empty housing resembles a banjo. The carrier is removed from the front of the housing, and is retained by 10 nuts on studs in the housing. The rear of the housing is smooth with a non-removable rear cover that is welded onto the main housing. The housing and axle tubes are made from stamped and welded steel.
The 8-3/4" axle was the primary axle assembly used in most non-compact car lines through 1972. It was also used in some high performance compact cars. Of the many axle types that Chrysler used since 1960, it was also the only axle assembly developed by Chrysler. It was phased out because it was more expensive to manufacture than using the outsourced Spicer 7.25", 8.25" and 9.25" units.
There are three basic types of 8.75" carriers available, which are distinguished by their drive pinion stem diameter. The choice of axle pinion assembly was determined based on a combination of vehicle horsepower and weight. Below are the 8.75" axle carrier types.
8.75" Axle Carrier Types and Years of Production
* ''741' Casting - 1 3/8" (1.375") Small Stem Pinion.
Carrier casting numbers were 1820657 (1957-1964) and 2070741 (1964-1972). This unit was usually used in low weight/medium horsepower and high weight/low horsepower applications. Although it is the weakest of the 8.75" units, it is still a stout unit, and is stronger than the Spicer-built Chrysler 8.25" rear. The 1 3/8" pinion is also larger than the pinion in the Ford 9" rear.
* ''742' Casting - 1 3/4" (1.75") Large Stem Pinion.Carrier casting numbers were 1634985 (1957-1964) and 2070742 (~1961-1969). This assembly was replaced by a phase-in of the 1-7/8" pinion '489' casting starting in the 1969 model year. This assembly was typically used in high weight/medium horsepower applications through high weight/high horsepower applications. Although not generally considered to be stronger then the '489' carrier, the '742' carrier is extremely stout, and is favored by many Mopar enthusiasts because they are easier to set up. Noted Mopar enthusiast John Kunkel mentioned that the biggest advantage of the 742 carrier is that it has the largest rear pinion bearing of all the 8 3/4" carriers. The larger bearing helps to prevent pinion deflection better under a load than the others. It also has a larger pinion than the Ford 9" rear.
* '489' Casting - 1-7/8" (1.875") Tapered Stem Pinion Carrier casting numbers were 2881488 or 2881489 (1969-1974). This assembly was introduced in 1969 and was phased-in to replace the 1-3/4" pinion '742' unit through 1970. Note: the 1-3/4" pinion also appeared in some '489' carriers during this period. By 1973, the '489' was the only unit available in passenger car applications, and was typically used in high weight/medium horsepower applications through high weight/high horsepower applications. This carrier is considered to be the strongest by some Mopar enthusiasts. Because it requires a crush sleeve to set bearing preload, some Mopar enthusiasts prefer the '742' casting. This is not really an issue now because there are now parts available to eliminate the crush sleeve. The '489' and the whole 8 3/4 unit in general is highly under rated I would put one up against a Ford 9" inch any day, I raced them for years with Monster Torque 440s and HEMIs coupled to them, and I never broke a rear, but I have wrung two drive shafts into.:grin:
Carrier Identification:
All 8-3/4" carrier assemblies can be identified externally by the casting numbers. The casting numbers are cast onto an ID pad on the driver's side of the carrier just behind the 'snout' of the case where the yoke attaches to the pinion. In addition to the casting numbers:
* The '741' will usually have a large 'X' cast on the left side
* The '742' will usually have a large '2' cast on the left side
* The '489' will have a large '9' cast on the left side.
Gear Ratio and Sure-Grip Identification:
Through 1965, the factory ratio was stamped on the identification boss, followed by an 'S' if it had a Sure Grip. After 1965, a tag was affixed under one of the carrier mounting nuts to identify the ratio. If it had a Sure Grip, an additional Sure Grip lube tag was sometimes added. Later year versions sometimes had the filler plug painted orange.
Gear Selection:
Because of its popularity, a wide range of gear selections is available for the 8.75" unit. Gear ratios available on the 8-3/4" axle through the years include, but are not limited to: 2.76, 2.93, 3.23, 3.31, 3.55, 3.73, 3.91, 4.10, 4.56, 4.89, 5.17 and 5.57.
Interchange Notes:
Any complete 8.75" carrier will interchange with another 8.75" carrier in any 8.75" housing. The Sure-Grip assemblies also interchange. However, none of the other separate parts such as cases, pinions and bearings will interchange.
