What gear ratio do I have in my GM or Chevrolet rear end, do I have positraction

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Rear End & Differential Ring Gear and Pinion Sets

What gear ratio do I have in my GM or Chevrolet

Differential Axle Codes

What is my rear differential ratio?

Identifying Vehicles Equipped with OE Traction Adding Differentials

General Motors Production Options.

Find General Motors Differential Parts and Accessories at the following links:

GM 7.5" Rear End Parts & Accessories
GM 8.5" 10 Bolt Rear End Parts & Accessories
GM 8.875" 12 Bolt Car Rear End Parts & Accessories
GM 8.875" 12 Bolt Truck Rear End Parts & Accessories
GM 9.5" Rear End Parts & Accessories
GM 10.5" Rear End Parts & Accessories
GM 11.5" Rear End Parts & Accessories

Differential cover/cover gasket shapes a common technique to identify differential ring gear diameter.

Dana/Spicer Differential Parts how to locate bill of material number and find correct parts .

The most accurate method of determining a rear axle gear ratio is to look in the vehicle manufacturer's service manual. The following Regular Production Option (RPO) codes identify the rear axle and trans axle overall final drive gear ratio's. These codes can be located on the RPO sticker in the glove box or in the trunk on most GM vehicles. These codes are arranged in alphanumeric order. Please refer to the information below

RPO Code	Ratio	Axle Type
F16	2.53	Front
F17	2.84	Trans axle
F18	2.65	Front
F25	3.32	Front
F29	2.41	Front
F36	2.19	Front
F45	2.93	Front
F47	2.73	Front
F57	3.15	Front
F62	2.39	Trans axle
F67	3.19	Front
F68	3.45	Trans axle
F75	3.18	Trans axle
F77	3.73	Trans axle
F79	2.97	Trans axle
F82	3.23	Trans axle
F83	3.05	Trans axle
F90	2.73	Front
FA0	5.77	Rear
FA1	4.88/6.94	Rear 2-speed
FA2	4.88/6.94	Rear 2-speed
FH4	3.94	Front
FH4	4.29	Front
FH4	3.03	Front
FH5	2.81	Trans axle
FH6	3.64	Front
FH7	4.12	Trans axle
FH8	2.40	Front
FH9	2.60	Trans axle
FJ1	4.18	Front
FJ2	3.74	Front
FJ3	3.35	Trans axle
FJ4	4.53	Front
FJ5	4.19	Front
FJ7	4.56	Front
FP0	3.62	Front
FP0	2.55	Trans axle
FP1	2.26	Front
FP1	2.72	Trans axle
FP2	3.58	Trans axle
FP3	2.73	Trans axle
FP4	2.69	Trans axle
FP7	3.73	Trans axle
FP8	3.29	Front
FP8	3.54	Trans axle
FP9	3.55	Trans axle
FQ2	3.48	Trans axle
FQ3	2.86	Trans axle
FQ4	3.57	Trans axle
FQ8	2.96	Trans axle
FQ9	3.21	Trans axle
FR2	2.93	Trans axle
FR3	3.69	Trans axle
FR6	3.84	Trans axle
FR7	3.95	Trans axle
FR8	4.17	Front
FR9	3.29	Trans axle
FV0	3.67	Trans axle
FV1	3.72	Trans axle
FV2	4.18	Trans axle
FV3	3.11	Trans axle
FV4	3.71	Trans axle
FV5	4.19	Trans axle
FV6	4.24	Trans axle
FV7	4.29	Trans axle
FV8	4.31	Trans axle
FV9	4.53	Trans axle
FW2	3.06	Trans axle
FW3	2.33	Front
FW3	4.02	Trans axle
FW4	3.36	Front
FW4	3.89	Trans axle
FW5	4.10	Trans axle
FW6	2.14	Front
FW6	3.42	Trans axle
FW7	3.83	Trans axle
FW8	1.99	Front
FW8	4.28	Trans axle
FW9	3.43	Trans axle
FX1	3.94	Trans axle
FX2	2.66	Front 1984-1985
FX2	3.91	Front 1995-2002
FX4	3.65	Trans axle
FX8	3.61	Trans axle
FY1	3.63	Trans axle
FY3	3.79	Trans axle
FY5	3.52	Trans axle

RPO Code	Ratio	Axle Type
G44	3.07	Rear
G72	2.14	Rear
G75	3.62	Rear
G84	3.70	Rear
G90	3.15	Rear
G91	6.83	Rear
GH0	3.54	Rear
GH4	3.55	Rear
GH4	2.29	Rear
GH4	2.77	Rear
GH4	2.28	Rear
GH7	2.73	Rear
GJ1	5.38	Rear
GJ2	5.13	Rear
GK7	4.78	Rear
GK8	4.33	Rear
GK9	4.63	Rear
GL0	5.13	Rear
GL3	6.17	Rear
GM1	2.59	Rear
GM2	3.44	Rear
GM3	3.45	Rear
GM4	3.67	Rear
GM5	3.89	Rear
GM6	4.22	Rear
GM7	3.68	Rear
GM8	2.56	Rear
GN9	4.11	Rear
GS4	2.70	Rear
GS8	3.94	Trans axle
GT4	3.73	Rear
GT5	4.10	Rear
GT6	4.19	Trans axle
GT7	3.33	Rear
GT8	4.10	Rear
GU1	2.41	Rear
GU2	2.73	Rear
GU3	2.93	Rear
GU4	3.08	Rear
GU5	3.23	Rear
GU6	3.42	Rear
GU7	2.77	Rear
GU8	3.90	Rear
GU9	3.91	Rear
GV0	3.55	Rear
GV2	5.83	Rear
GV3	3.57	Rear
GV4	3.36	Rear
GV5	3.82	Rear
GV7	4.05	Rear
GV8	2.72	Rear
GV9	4.25	Rear
GW4	3.31	Rear
GW6	3.27	Rear
GW9	2.93	Rear
GX3	3.33	Trans axle
GX4	3.75	Rear
GX5	4.09	Rear
GX6	3.53	Rear
GX8	3.74	Trans axle
GY2	4.30	Rear
GY3	4.29	Trans axle
GY4	4.53	Rear
GY5	3.65	Front
GY7	4.18	Trans axle
GY9	4.31	Rear

RPO Code	Ratio	Axle Type
H42	6.17	Rear
H43	5.43	Rear
HA3	5.29	Rear
HA5	4.63	Rear
HC2	4.27	Rear
HC4	4.56	Rear
HC7	5.13	Rear
HC8	3.21	Rear
HC9	5.13	Rear
HD1	5.83	Rear
HE3	3.07	Rear
HE4	3.40	Rear
HF7	4.56	Rear
HF8	4.88	Rear
HJ1	4.55	Rear
HJ2	5.86	Rear
HJ3	4.75
HJ4	6.50	Rear
HJ5	5.57	Rear
HJ6	4.78	Rear
HJ7	4.88	Rear
HK1	2.87	Rear
HK3	6.14	Rear
HK9	5.86	Rear
HO4	4.11	Rear
HO6	4.63	Rear

The following figure presents differential cover/cover gasket shapes. Counting cover bolts and cover shapes is a common method to determine which ring gear diameter differential you have in your rear wheel drive vehicles. See following paragraph for selection of correct Dana parts.

When ordering Dana/Spicer Differential Parts provide bill of material number. This number is stamped on your right hand side axle tube. It's a number like 603XX-X, 604XX-X or 605XX-X. With this number you can tell exactly what components the factory used in the assembly of your differential.

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