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Yukon Gear ZG GM12P-390 Ring and Pinion Gear Set GM 12-Bolt Car 3.90 Ratio
The Yukon Gear ZG GM12P-390 is a ring and pinion gear set for the GM 12-bolt car rear differential in a 3.90 gear ratio. The GM 12-bolt car differential was used in 1964-1972 GM A-body muscle cars including the Camaro, Chevelle, Nova, GTO, and numerous others. Manufactured to exceed OEM specifications, each ZG GM12P-390 gear set undergoes rigorous in-house quality evaluation. Yukon's Lifetime Warranty is included, and Magnuson-Moss protections apply for drivetrain warranty claims.
Key Features
- Exceeds OEM specifications — rigorous in-house dimensional, material, and fitment testing
- 3.90 gear ratio — a performance-oriented ratio suited for strip and street performance builds
- Fits GM 12-bolt car differential — 1964-1972 GM A-body and F-body muscle car applications
- Yukon Lifetime Warranty — Magnuson-Moss protections apply for drivetrain warranty claims
What's Included
- 1x Yukon ZG GM12P-390 ring gear
- 1x Yukon ZG GM12P-390 pinion gear
Specifications
| Specification | Detail |
|---|---|
| MPN | ZG GM12P-390 |
| UPC | Not available |
| Differential | GM 12-bolt car |
| Gear Ratio | 3.90 |
| Warranty | Yukon Lifetime Warranty (Magnuson-Moss applies) |
| Fitment | 1964-1972 GM 12-bolt car differential (A-body and F-body) |
This Part Fits
| Year | Make | Model |
|---|---|---|
| 1964-1972 | Buick | Wildcat |
| 1964-1972 | Chevrolet | Bel Air / Biscayne / Camaro / Caprice / Chevelle / El Camino / Impala / Monte Carlo / Nova |
| 1970-1972 | Pontiac | GTO / Trans Am |
Frequently Asked Questions
-
Q: What vehicles use the GM 12-bolt car differential?
A: The GM 12-bolt car differential was used in 1964-1972 GM A-body and F-body muscle cars, including the Camaro, Chevelle, Nova, Impala, Chevrolet Bel Air, El Camino, Monte Carlo, Buick Wildcat, Pontiac GTO, and Pontiac Trans Am. -
Q: Is the GM 12-bolt car the same as the GM 12-bolt truck?
A: No. The GM 12-bolt car and GM 12-bolt truck are different differentials with different ring gear diameters and bolt patterns. The ZG GM12P-390 fits the car version only. -
Q: What ratio does this listing cover?
A: 3.90 ratio. Yukon offers multiple ratios for the GM 12-bolt car; contact your dealer for other ratios. -
Q: Do I need an overhaul kit with this gear set?
A: Yes. A master overhaul kit (bearings, races, seals) should be replaced simultaneously for optimal results. -
Q: What is included?
A: Ring gear and pinion gear only. Bearings, seals, and hardware are sold separately. -
Q: Does Yukon offer a warranty?
A: Yes. Yukon Gear provides a Lifetime Warranty. Magnuson-Moss protections apply for qualifying drivetrain applications. -
Q: Is professional installation required?
A: Yes. Differential ring and pinion installation requires precise shimming and setting, specialized tooling, and experience. Professional installation is strongly recommended. -
Q: What posi unit is compatible with the GM 12-bolt car?
A: The GM 12-bolt car is compatible with various positraction (Eaton, Auburn, OEM GM Posi) units. Confirm compatibility with your specific unit before ordering.
Installation Instructions
Ring and pinion installation requires specialized tooling and expertise. Set pinion depth to specification using Yukon's installation guide and shim pack. Install carrier bearings, set backlash to 0.005 to 0.009 in. (or per OEM), and verify gear contact pattern with marking compound before final assembly. Torque all ring gear bolts to OEM specification. Fill with the correct gear oil and friction modifier if applicable.
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