Rear Axle Codes

More Chassis Information & casting numbers at bottom of page

10-bolt vs. 12-bolt axle ratios

1964 [ 1965 ] [ 1966 ] [ 1967 ] [ 1968 ] [ 1969 ] [ 1970 ] [ 1971 ] [1972 ] [ Top ]

1965 - [ 1964 ] [ 1966 ] [ 1967 ] [ 1968 ] [ 1969 ] [ 1970 ] [ 1971 ] [ 1972 ] [ Top ]

1965 to 1969 production numbers are stamped on the bottom left or right axle tube either adjacent to the carrier housing or about 8" - 10" inboard from the backing plates. Example: CG1025B decodes to CG ~ 3.36 Positraction, 1025 ~ Month [Oct] and Day [25], B ~ Buffalo (G=Chevrolet Gear & Axle, W=Warren, K=McKinnon Industries) CG 0629 B ~ Positraction 3.36, June 29, Buffalo CX 0909 B ~ 3.07, September 9, Buffalo
CA	3.08
CB	3.36
CC	3.73
CD	3.07 ~ Positraction
CE	3.08 ~ Positraction
CF	3.31 ~ Positraction
CG	3.36 ~ Positraction
CH	3.70 ~ Positraction w/Metallic Brakes
CI	3.73 ~ Positraction
CJ	3.07 ~ w/Metallic Brakes
CK	3.07 ~ Positraction w/Metallic Brakes
CL	3.08 ~ w/Metallic Brakes
CM	3.08 ~ Positraction w/Metallic Brakes
CN	3.31 ~ w/Metallic Brakes
CO	3.31 ~ Positraction w/Metallic Brakes
CP	3.36 ~ w/Metallic Brakes
CQ	3.36 ~ Positraction w/Metallic Brakes
CH	3.70 ~ w/Metallic Brakes
CR	3.70 ~ Positraction
CS	3.70 ~ Positraction w/Metallic Brakes
CT	3.73 ~ w/Metallic Brakes
CU	3.73 ~ Positraction w/Metallic Brakes
CV	3.70 ~ Overdrive
CW	3.31 ~  "327" w/Air Conditioning
CX	3.07 ~  "327"
GA	3.31 ~ Heavy Duty
GB	2.73 ~ 327 w/Powerglide
GC	2.73 ~ Positraction
GD	2.73 ~ Metallic Brakes
GE	2.73 ~ Positraction w/Metallic Brakes

1966 - [ 1964 ] [ 1965 ] [ 1967 ] [ 1968 ] [ 1969 ] [ 1970 ] [ 1971 ] [ 1972 ] [ top ]

1965 to 1969 production numbers are stamped on the bottom left or right axle tube either adjacent to the carrier housing or about 8" - 10" inboard from the backing plates. Example: CB1012W decodes to CB ~ 3.36, 1025 ~ Month [Oct] and Day [12], W ~ Warren (B=Buffalo, G=Chevrolet Gear & Axle, K=McKinnon Industries) CB ~ 3.36, October 12, Warren
CA	3.08
CB	3.36
CC	3.73
CD	3.07 ~ Positraction
CE	3.08 ~ Positraction
CF	3.31 ~ Positraction
CG	3.36 ~ Positraction
CH	2.73 ~ Positraction
CI	3.73 ~ Positraction
CJ	3.07 ~ w/Metallic Brakes
CK	3.07 ~ Positraction w/Metallic Brakes
CL	2.73 ~ Positraction
CM	2.73 ~ Positraction w/Metallic Brakes
CN	3.31 ~ w/Metallic Brakes
CO	3.31 ~ Positraction w/Metallic Brakes
CR	3.70 ~ Positraction
CS	2.56 ~ w/Metallic Brakes
CT	3.73 ~ w/Metallic Brakes
CU	3.73 ~ Positraction w/Metallic Brakes
CV	3.70
CW	3.31
CX	3.07
CY	3.07
CZ	2.73
KA	3.55
KB	3.55 ~ Positraction
KC	2.73 ~ Positraction
KD	2.73
KE	2.56 ~ Positraction
KF	3.55 ~ Positraction
KG	3.55 ~ Positraction w/Metallic Brakes
KH	3.55 ~ w/Metallic Brakes
KI	2.56 ~ Positraction w/Metallic Brakes
KJ	3.55
KK	4.10 ~ Positraction
KL	4.10 ~ w/Metallic Brakes
KM	4.56 ~ Positraction
KN	4.56 ~ w/Metallic Brakes
KO	4.88 ~ Positraction
KP	4.88 ~ w/Metallic Brakes
KQ	2.73 ~ w/Metallic Brakes
KR	2.73 ~ Positraction w/Metallic Brakes
KS	3.07 ~ w/Metallic Brakes
KT	3.07 ~ Positraction w/Metallic Brakes
KU	3.31 ~ w/Metallic Brakes
KV	3.31 ~ Positraction
KW	2.73 ~ Positraction
KX	3.07 ~ Positraction
KY	3.31
KZ	3.31

1968 - 1964 ] [ 1965 ] [ 1966 ] [ 1967 ] [ 1969 ] [ 1970 ] [ 1971 ] [ 1972 ] [ top ]

1969 - [ 1964 ] [ 1965 ] [ 1966 ] [ 1967 ] [ 1968 ] [ 1970 ] [ 1971 ] [ 1972 ] [ top ]

1970 production numbers are stamped on the bottom left or right axle tube either adjacent to the carrier housing or about 8" - 10" inboard from the backing plates. Example: CGI0629B decodes to CGI ~ 3.36 Positraction, 0629 ~ Month [June] and Day [29], B ~ Buffalo (G=Chevrolet Gear & Axle, W=Warren, K=McKinnon Industries). If a "1" or "2" exists, it indicates the plant shift number. CCF ~ Positraction 3.31 - November 6, Buffalo, 1st shift CRV ~ Positraction 3.31 - December 22, Buffalo, 1st shift CCF ~ Positraction 3.31 - April 8, Buffalo, 2nd shift
CGD	2.73 ~ Positraction
CCH	2.73 ~ Positraction
CCD	3.07 ~ Positraction
CCP	2.73
CCA	3.08
CGA	2.56
CGC	2.73
CGF	3.08
CGG	3.36
CGB	2.56 ~ Positraction
CGI	3.36 ~ Positraction
CCN	2.56
CKD	2.73
CCX	3.07
CCW	3.31
CKJ	3.55
CCO	2.56 ~ Positraction
CCF	3.31 ~ Positraction
CKF	3.55 ~ Positraction
CKK	4.10
CKC	2.73 ~ Positraction
CCE	3.08 ~ Positraction
CRJ	2.56
CRK	2.56 ~ Positraction
CRU	3.31
CRV	3.31 ~ Positraction
CRW	4.10

1971 - [ 1964 ] [ 1965 ] [ 1966 ] [ 1967 ] [ 1968 ] [ 1969 ] [ 1970 ] [ 1972 ] [ top ]

1971 and 1972 production numbers are stamped on the front of the right axle tube  inboard of the upper control arm bracket approx 30-45 degrees above horizontal. Example: CHC0642E decodes to CHC ~ 2.73 Positraction, 064 ~ day of year starting with January 1 (64th day), 2 ~ shift (if present), - ~ no Positraction, p ~ Positraction, E ~ Eaton Positraction B=Buffalo, G=Chevrolet Gear & Axle, W=Warren, K=McKinnon Industries CH ~ Positraction 2.73, March 5 (64th day of year), 2nd shift, Eaton Positraction KD ~ 2.73, K ~ McKinnon Industries, January 11th (11th day of year)
GD	2.73 ~ Positraction
GF	3.08
CH	2.73 ~ Positraction
GA	2.56
GC	2.73
GG	3.36
GB	2.56 ~ Positraction
GI	3.36 ~ Positraction
KD	2.73
CW	3.31
CF	3.31 ~ Positraction
RU	3.31
RV	3.31 ~ Positraction
RW	4.10
GH	2.73
GN	3.08

1972 - [ 1964 ] [ 1965 ] [ 1966 ] [ 1967 ] [ 1968 ] [ 1969 ] [ 1970 ] [ 1971 ] [ top ]

Chevelle 10-bolt vs. 12-bolt ratios

12 bolt

10 bolt

More Chassis Information

Casting Numbers:
12-Bolt Housing: Casting #
1965 Chevelle 3859140N
1966 Chevelle 3875745N
1967 Chevelle N 3894939
1967 Chevelle-Late NF X 3917124
1968-Early 1969 Chevelle NF X 3917124
1969 Chevelle 3959038 NF
1970-72 Chevelle 3969278NF
1970-72 Chevelle 3969278

10-Bolt Housing: Casting #
1964 Chevelle 3839390N
1965 Chevelle 3959139N
1966 Chevelle 3875744N
1967 Chevelle 3894938N
1968 Chevelle 3917123NF
1969 Chevelle 3859037NF
1970-72 Chevelle 3969277NF

Several variations of no suffix letters, ore letters like "N", "NF" and "X" have been found on rear end housing castings. Significance of these letters, or lack of, isn't know.

Thanks to Dave Bates for his listing of casting numbers.

The date code on a rear end housing is simple to decode. It includes the month, day and year such as J257. This decodes to October 25, 1967. Month codes are A through L for January through December.

Casting date example of August 20, 1964

Casting date example of June 4, 1965

Casting date example of June 21, 1967

Casting date example of February 18, 1968

Casting date example March 5, 1970

Foundry castings of 12345 67890 - Casting date of December 19, 1968.

All Chevelle rear ends are of the Salisbury design. A Salisbury rear end is very easy to distinguish from the Hotchkiss design. The Salisbury rear end has a removable cover on the rear of the center section where the Hotchkiss does not.


Typical Salisbury rear end found on 1964-1972 Chevelles.


Typical Hotchkiss rear end found on 1957-1985 Fords.

The Hotchkiss is generally favored over the Salisbury in racing circles due to the fairly quickly removable center section allowing a racer to have several gear ratios available to be swapped relatively quickly as the situation warrants.  

* 1964-67 Chevelle rear ends were manufactured by the Chevrolet Gear and Axle Division.  The housing measures 53.25 inches from backing plate to backing plate and with the brake drums in place, the total width is 60.00 inches.

* 1968-72 Chevelle rear end housings measure 58.5 inches from flange to flange, and with the brake drums in place, the total width is 62.5 inches. (Note: Other sources put the total width at 61.125" to 61.25".)

The 10 bolt Chevelle rear end has the 8.2" ring gear from 1964 to 1972.  It wasn't until late 1972 that the 10 bolt 8.5" ring gear was used in Chevelles although many aftermarket parts listings show 70-76 for the 8.5" rear end for Chevelles.

Rear spring mounting pads differed in that 1964-66 rear ends used a flat pad with a hole drilled in the center while 1968-72 rear ends have circular spring mounting pads, which are 3/4" higher that the early flat pad.

1967 was a transition year in that A-cars might have a 1964-66 style rear end, a 1968-72 rear end (which is wider, and commonly available), or a "hybrid" rear end, which will have the 58.5" width, but with the early spring mounting pad and trailing arm brackets. (Note: For what it's worth, ALL 67 rear ends I've ever seen were the narrow variety and used the spring cup like 68-72 but were narrower like the 64-66.)

Rear upper control bushing eyes differ, and the positioning of the bushing eyes will differ. 1968-72 rear end housings will have a 3/8" forward positioning, which is farther than 1964-67 rear ends.

1964 was the only year that the rear end bushing are small, and any upper trailing arm (from any GM division) will fit 1964 rear end housings.

Upper trailing arms of 1964-67 vintage interchange, and they are 1" shorter, which will not fit into 1968-72 A-cars. 1968-72 A-cars have longer upper arms, and when switching upper arms, be careful here, in which the pinion nose angle might be affected. According to Inside '64 -- '72 A-Bodies, (Car Craft Magazine) there are 10 different rear upper control arms offered. Other characteristics include clearance bulges, common with 12-bolt differentials in A-cars, and adjustable upper arms, optioned on Oldsmobile A-cars (F-85, Cutlass). 442s had boxed upper arms, and this is a sought-after item in a restoration.

On 1968-72 A-cars, like high-performance, 4-speed, and Monte Carlo/Grand Prix, there is a triangulation brace bracket that is standard. This stiffens the chassis, and tubular versions are available from Edelbrock and Hotchkis Performance.

Note: the trailing arms fit either side, and this means that the left upper arm will fit on the right, and vice versa.

CONTROL ARMS (FRONT)

Most of the control arms for the 1964-72 Chevelle interchange, and the lower control arm used for the front suspension had these distinct features.

Note: the lower arms may differ, in case a replacement or factory mismatch are common when locating the correct lower arm for a restoration. The only problem with oval bushings is that the existing bushing cans will have to be reused, and aftermarket companies that use solid or Del-A-Lum (a Global West product) bushings as replacements might require locating a set of round bushing lower arms, either a 1.90" or 1.625".

*Upper control arms for Chevrolet Chevelles and El Caminos use cross shafts that used bolts to secure the cup washer to the bushing. BOP A-Bodies used cross shafts with threaded ends with locknuts. Due to the possibility of frame spread, MOOG or TRW manufactures an offset control arm shaft that allows the camber angles to be corrected via OEM specs.

FRONT SPRINGS

The springs vary with application and chassis packages, but there is one thing that is important: 1968-72 A-cars have a different front spring diameter when compared to 1964-67 front springs ("Knuckle Sandwich", Hot Rod, 6/87). 1969-present springs are based on computerized data concerning chassis package and body styles, but the rates vary, depending whether a softer or stiffer ride is preferred.

Note: 1964-67 front springs can be found on 1967-69 Camaros and 1968-74 Novas, but the spring rates will differ; 1968-72 A-body front springs are used on 1968-70 BOP full size cars, but the spring rates vary.

REAR SPRINGS

The data that are true for front springs is the same for rear springs, and 1964-66 rear ends have provisions for bolting on the spring to the pad.

Another difference is that 1964-66 springs are pigtailed on one end only while 1967-72 rear ends use a cup and is flanged to hold the spring in place.

Webs By Dale
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