Chrysler 8 3/4” Axle Guide
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Don't remember where I found this one. Maybe at
Allpar.com?
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General
The Chrysler 8-3/4" rear axle assembly was introduced in 1957. It is a
banjo-type (Hotchkiss) axle, ie. the differential is contained in a removable
carrier assembly which is extracted from the axle housing toward the front of
the car. It is retained by 10 nuts on studs in the housing. The differential
“cover” (although permanent) as viewed from the back of the car is smooth and
hemispherical; it is welded onto the main housing. The axle tubes are part of
the overall housing. The axle has an 8-3/4" diameter ring gear. There are
three basic types available distinguished by their drive pinion stem diameter.
The 8-3/4" axle was the primary axle assembly used in most Chrysler car lines
through 1972.
Handy Dandy ID Picture
(click to enlarge!)
Where To Find One
The first thing one needs to know in order to find the right axle for the job is the Chrysler platform code system. With an understanding of the different vehicles involved, you can then determine which one will best suit your application.
A-body models include:
1964-76 Plymouth Valiant, 1964-69 Plymouth Barracuda, 1970-76 Plymouth Duster,
1972-76 Plymouth Scamp, 1964-76 Dodge Dart, 1971-72 Dodge Demon, 1973-76 Dodge
Dart Sport, 1969-76 Dodge Dart Swinger
B-body models include:
1965-70 Plymouth Belvedere, 1965-74 Plymouth Satellite, 1968-74 Plymouth Road
Runner, 1970 Plymouth Superbird, 1967-71 Plymouth GTX, 1965-74 Dodge Coronet,
1968-71 Dodge SuperBee, 1966-74 Dodge Charger, 1969 Dodge Charger Daytona
C-body models include:
All 1965-74 full-size Chrysler models (Newport, New Yorker, Imperial), 1965-74
full size Dodge and Plymouth models (Polara, Monaco, Fury, Sport Fury, etc.)
E-body models:
1970-1974 Plymouth Barracuda and 1970-1974 Dodge Challenger
Axles and Housings
Because the 8-3/4" axle was available in most body lines, there are a variety of housings available. Following are SOME of the passenger car axle dimensions and notations. The 'Perches' dimension is the distance center to center between the spring mount perches. Dimensions are in inches.
Body line Track Perches Notes
------------- ---------- ----------- -----------------------
A-body, 65-72 55.6 43.0 4" lug bolt circle,
offered in heavy duty apps.
B-body, 62-70 59.2 44.0
B-body, 71-72 62.0 47.3
B-body, 71-72 63.4 47.3 station wagon
C-body, 64-72 63.4 47.3
D-body, 64-72 63.4 47.3
E-body, 70-74 60.7 46.0
The 8-3/4 was also available in the 58-74 D100/W100 trucks (and variants), the 64-70 A-100 trucks and vans, the 67-70 A-108 trucks and vans, the 71-74 B100/B200 vans and non-listed 57-64 full and mid-size car models.
Notes:
1) The axle centerline to yoke/universal centerline is 12.35" for the 8-3/4"
axle.
2) Any 8-3/4" center section may be interchanged for another as an entire
assembly.
3) All 8-3/4" axle shafts, 65-74, are retained by a bolt-on flange. Axles can
be
interchanged within housings of the same width. The passenger side axle has
a
threaded adjuster to set axle shaft end play.
4) There was a slight dimensional change in axle shaft length when the Sure Grip
design
changed. If interchanging axles with the slight difference, the threaded
end play
adjustment can be used to accommodate it.
5) The 57-64 8-3/4 axle drive shafts were tapered and used a keyway and locknut
to retain
the brake assemblies and end play was set with shims. The 65 and later
units use
flanged axle shafts and a threaded adjuster to set axle end play.
6) See Appendix A for information about the A-body 8-3/4" axle and bolt circle
changes.
Handy Dandy Picture For Reference
(click to enlarge!)
Center Section Types
The 8-3/4" axle was available in three basic types. The types are differentiated by the pinion stem diameter....1-3/8", 1-3/4", 1-7/8". The choice of axle pinion assembly was determined based on the application. Differential bearing setting (ie. backlash ) is set with threaded adjusters on all carriers. All 8-3/4" carrier assemblies can be identified externally by the casting numbers.
1-3/8" small stem pinion (aka. '741')
Carrier casting numbers: 1820657 (1957-1964), 2070741 (1964-1972).
This assembly was typically used in low weight/low horsepower applications
through low weight/medium horsepower and high weight/low horsepower
applications.
Pinion depth and bearing preload is set with shims.
1-3/4" large stem pinion (aka. '742')
Carrier casting numbers: 1634985 (1957-1964), 2070742 (~1961-1969).
This assembly was replaced by a phase-in of the 1-7/8" pinion starting in the
1969 model year. 1970 RW (Plymouth and Dodge mid-size) were the last models to
use the 1-3/4" which appeared in a 2881489 case. This assembly was typically
used in high weight/medium horsepower applications through high weight/high
horsepower applications.
Pinion depth and bearing preload is set with shims.
1-7/8" tapered stem pinion (aka. '489')
Carrier casting numbers: 2881488, 2881489 (1969-1974).
This assembly was introduced in 1969 and was phased-in to replace the 1-3/4" 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. This assembly was typically used in high weight/medium
horsepower applications through high weight/high horsepower applications.
Pinion depth is set with shims, preload is set with a crush sleeve.
The '741' commonly has a large X cast on the left side, the '742' may have a large 2 cast on the left side, and the '489' has a large 9 cast on the left side. Through 1965, the factory ratio was stamped on the identification boss, followed by an 'S' if Sure Grip equipped. After 1965, a tag was affixed under one of the carrier mounting nuts to identify the ratio. If Sure Grip equipped, an additional Sure Grip lube tag was sometimes affixed; later years sometimes had the filler plug painted orange.
Gear ratios available on the 8-3/4" axle through the years include: 2.76, 2.93, 3.23, 3.31, 3.55, 3.73, 3.91, 4.10, 4.56, 4.89, 5.17, 5.57. On OEM gear sets, the ratio is usually stamped on the ring gear edge. Ratio may be determined by the number of teeth on the ring gear divided by the number of teeth on the pinion gear or by counting the ratio of the number of turns of the pinion relative to one turn of the axle shaft.
The 8-3/4" center section is removed from the front of the housing. To
remove the center section, remove the wheels, brake drums, and drive shaft
(note: pre- 65 units have a pressed-on brake hub...requires a puller for
removal). Remove the axle shafts, 5 bolts on the backing plate flange on post
64 units, use puller for pressed-in pre-65 units. Remove the 10 nuts on the
housing studs around the carrier perimeter. Remove the carrier...may require
prying, fluid will drain when carrier gasket seal is broken.
Sure Grip
Sure Grip is the Chrysler name for a limited slip differential. It was optional on the 8-3/4" axles, 1958-1974. Two styles were used.
1958-1969 used the Dana Power-Lok (# 2881487). This unit utilized clutches for the differential locking action. The Power-Lok can be rebuilt using kit # 2070845 ( Mopar Performance [MP] # P4529484 ). In this assembly, axle driveshaft end thrust is taken by the thrust block assembly (replacement # 2881313). This Sure Grip appeared in the '741' and '742' assemblies. The axle bearings are: 25590 (Timken cone), and 25520 (Timken cup), (Chrysler numbers 1790523 and 696403). The Dana Power-Lok can be recognized by its bolt-together assembly, bolts around the side opposite the ring gear, and multiple openings exposing the cross shafts.
1969-1974 used the Borg Warner Spin Resistant (# 2881343). This unit utilized a spring-preloaded cone friction arrangement for the locking action. Axle end thrust is taken by the cross shaft. This Sure Grip appeared in '489' assemblies and 70 and later '741'/'742' assemblies. The differential axle bearings are: LM 104912 (Timken cone), and LM 104949 (Timken cup), (Chrysler numbers 2852729 and 2852728). The Borg Warner Spin Resistant unit can be recognized by its lack of bolts on the side opposite the ring gear (like the Dana), and two openings exposing the preload springs. Borg Warner sold this design to Auburn Gear who currently offers the replacement Sure Grip assemblies.
Non-Sure Grip differentials can be identified by the large openings in the differential exposing the differential (aka. spider) gears. There are no springs or clutches.
Interchange Notes:
The two Sure Grip types can be interchanged between the carriers if the matching
differential axle bearings are retained. The outside diameter of the cups are
the same between the '741'/'742' and the '489'; the inner cone differs. The
Sure Grip differential can be used as a direct replacement for the non-Sure Grip
within the carrier/bearing limits previously noted.
Universal Joint Yokes
The 8-3/4" axle was offered with two size cross & roller style universal joint. These are referred to as the '7260' (2-1/8" yoke ID) and the '7290' (2-5/8" yoke ID). Most Imperials and some C-bodies used a different universal joint. The '1330' type joint was used on Imperials and others with a constant velocity joint. The '1330' uses outside snap rings instead of the inside snap rings used by the '7269' and '7290'. The cap diameter for the '7260' is 1.078". The cap diameter for the '7290' is 1.126". The '1330' style joint cap diameter is 1.063".
There are four different yokes that have been used with the 8-3/4" axle for the '7260' and '7290' style universal joints. The '741'/'742' assemblies used a coarse spline (10 splines) drive pinion. Most of the aftermarket gears also use this coarse spline yoke mount. There is a small yoke for the '7260' and a larger one for the '7290'. The '489' assembly used a fine spline (29 splines) yoke. Note: during the phase-in period of 69-71 for the '489' unit, there were several permutations of pinion size and yoke availability. 69-70 '489' units may be equipped with a coarse (10) spline pinion, particularly for the '7290'. There are two yokes for the '7260' and '7290' universal joints with fine (29) splines. Two additional yokes were used for the '1330' style universal joint in constant velocity applications, one for 10 splines and one for 29 splines.
Interchange Notes:
7260, 7290, 1330 yokes may be interchanged if the spline count is the same.
Note: the 9-1/4" axle (73-up) uses the same fine spline yokes as the 8-3/4"
fine spline units (29 splines).
Strength Considerations
Pinions
The 1-3/8" '741' pinion is the weakest. It is still a capable unit in most
moderate power, moderate traction street applications. For high torque
applications with high traction tires, the 1-3/4" or 1-7/8" should be
considered.
The 1-7/8" '489' is supposedly the strongest. Although the stem tapers down
along it's length, it appears inherently stronger from a pinion stem perspective
and the inherent strength of the fine spline (OEM gears).
The 1-3/4" '742' has a larger rear pinion bearing yielding greater strength in
this area. The 1-3/4" shares yoke mount diameter and mounting nut with the
1-3/8".
For perspective, the 7-1/4" has a 1-3/8" pinion, the 8-1/4 has a 1-5/8" pinion,
the 9-1/4" (70s) has a 1-7/8" pinion.
Sure Grips
The Dana Power-Lok is inherently stronger and provides better, equal torque
transmission to both axles. It's locking capability is also proportionate to
the applied torque. The Borg Warner unit is weaker, but is a more versatile
unit for practical street applications in inclement traction periods. The Dana
unit is the better of the stock sure grips for racing applications and has
clutch rebuild kits available. An updated cone-type sure grip unit is available
from Auburn Gear with 30% increased torque carrying capacity over the old
version. Lockers and spools are also available from various sources.
Service Parts Information
Most replacement parts for the 8-3/4" axle are still available. Some items not available are new Dana Power-Lok assemblies, most OEM gears, most carrier housings and complete differentials and housings. A revised version of the cone-type Sure Grips are available from Auburn Gear. The Power-Lok clutch kits are available from MP and other sources. Gear sets (typically performance oriented ratios) are available from MP and the aftermarket for the '489' and '742'. Bearings and seals are readily available.
Some sources
Mopar Performance dealers, Chrysler dealers.
Moser Engineering, 1616 Franklin St, Portland IN, 47371 (219-726-6689).
Reider Racing, 12351 Universal Dr., Taylor MI, 48180 (313-946-8672).
Aftermarket for general replacements, ie. seals, bearings, etc.
Selected Parts Reference
Numbers listed for reference, some may be superceded or discontinued, some variances among models/years may occur. Reference factory or replacement parts catalogs for exact replacement details.
Universal Joint Items
Item Chrysler Precision Dana TRW
(Detroit ref.) (OEM or MP) (Moog) (Spicer) (Federal Mogul)
-------------- ------------ --------- -------- --------------
7260 joint 4364400 315G 5-1306X 20030, 20030P
7290 joint 4057025 316 5-1309X 20059, 20059P
Combination * --- 347 --- 20226
1330 joint 2533202 354 5-213X 20064, 20064P
7260 strap kit P4120468 318-10 2-70-38X 20704
7290 strap kit P4120469 492-10 2-70-28X 20705
* This is a combination of the 7260 and 7290 universal joints to allow
mating of the two styles.
Yokes
3432485 -> 29 spline 7260 (2-1/8" ID), also P4529481
3432487 -> 29 spline 7290 (2-5/8" ID), also P4529483
3004872 -> 10 spline 7260 (2-1/8" ID), also P4529480
P4529482 -> 10 spline 7290 (2-5/8" ID), replaces 2808384, 3004873
2931813 -> 10 spline 1330, for constant velocity, i.e. Imperial.
3432489 -> 29 spline 1330, for constant velocity, i.e. Imperial.
1556556 -> pinion washer, concave, 3/16" thick, 13/16" hole diameter.
2070117 -> pinion washer, concave, 3/16" thick, 15/16" hole diameter.
1795175 -> pinion washer, flat, 3/32"thick, 13/16" hole diameter.
1795173 -> pinion nut, 3/4"-16 thread, 1-1/4" hex.
6027323 -> pinion nut, 3/4"-16 thread, 1-1/8" hex.
6028041 -> pinion nut, 7/8"-14 thread, 1-1/4" hex.
Sure Grip Items
Mopar Sure Grip axle additive - 4318060
Dana Power-Lock thrust block set - 2881313
Repair Kit, Dana Power-Lok - P4529484 (replaces 2070845)
Note: there is no repair kit for the Borg Warner/Auburn unit, but the internal
cones have been remachined by others to successfully restore performance.
Shim Package
1-3/4" pinion -> P4452027
1-7/8" pinion -> P4452026
Ring Gear Bolts
P4529486 -> 71 and later (also 4131255, pkg. of 10)
P5249163 -> 70 and earlier
Note: the 71 and later bolts may be installed in the earlier units by drilling a shoulder relief in the attachment holes.
Gaskets, Seals
Position Chrysler National C/R Fel-Pro
--------------- -------- -------- -------- --------
Axle inner seal 4796698 8695S 15460 ---
Axle outer seal 2404216 8704S 19000 ---
Axle flange, foam 2070933 see flange kit see flange kit 55032
Axle flange, shim 2881314 see flange kit see flange kit ---
Carrier gasket 1673367 --- --- RDS 65833
Pinion seal, 1-7/8 2931862 5126 18708 ---
Pinion seal, 1-3/4 2931862 7216 18912 ---
Pinion seal, 1-3/8 2931862 8515N 18708 ---
Yoke repair sleeve --- 99187 99187 ---
Bearings
Position Cup/Cone, Timken, BCA Notes:
------------- --------------------- ------------------
Differential, side LM 104949/LM 104912 70-74, Borg Warner
Differential, side 25590/25520 57-69, Dana
Pinion, front M88048/M88010 1-7/8"
Pinion, front HM89443/HM89410 1-3/4"
Pinion, front M88048/M88010 1-3/8"
Pinion, rear M804049/M804010 1-7/8"
Pinion, rear M803149/M803110 1-3/4"
Pinion, rear HM89446/HM89410 1-3/8"
Axle, outer BCA A-7 65-74
Axle, outer C/R BR7 65-74
Axle bearing service kit: Chrysler # 3683966, one axle.
BCA differential kit: 1-7/8", # RA-301, 1-3/4", # RA-300.
BCA axle mounting flange repair kit: Left # A-7-LK, Right # A-7-RK.
C/R axle mounting flange repair kit: Left # A7-LK, Right # A7-RK.
Vent bolt - Chrysler # 4032798
Spring mounting pads (perches) - Chrysler # P4120074
'489' collapsible spacer (pinion bearing preload) - Chrysler # 2931687
Mopar gear lubricant - 4318058
Mopar wheel bearing lubricant - 4318064
Note: the 8-3/4" axle shaft outer bearings require packing with grease as
they are not lubricated by the gear oil.