Yukon ZG GM12P-390 GM 12-Bolt Car 8.875in Ring Pinion 3.90 for 1964-1972

Regular price: $282.95
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Sale price: $282.95

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Product Specification:

SKU:YUKZG GM12P-390

MPN: ZG GM12P-390

UPC: 883584361695

Weight: 16.5 lb

Inventory: 2

Type: Final Drive Gears

Vehicle Fitment

1964-1972 Chevrolet Bel Air, Biscayne, Impala
1964-1972 Chevrolet Chevelle/Malibu
1964-1968 Chevrolet Chevy II/Nova
1965-1972 Chevrolet El Camino
1966-1970 Chevrolet Caprice
1967-1972 Chevrolet Camaro
1968-1972 Chevrolet Nomad
1970-1972 Chevrolet Monte Carlo
1964-1972 Buick Wildcat
1969-1972 Pontiac Firebird/Trans Am
1970-1972 Pontiac GTO

Fitment Notes

This is the GM 12-bolt passenger car differential (8.875" ring gear, oval-shaped cover) - a physically different, non-interchangeable axle from the "GM 12-bolt truck" differential used in G/K/C-series trucks and vans of the same era
Standard rotation only
This is a ring & pinion gear set only - it does not include bearings, races, shims, or seals; pair it with a separate install or master overhaul kit for a complete gear swap

Features

High-performance ring & pinion gear set for the GM 12-bolt passenger car differential
3.90 gear ratio
30-spline pinion
12 ring gear bolts
8.875" ring gear diameter
Manufactured by USA Standard Gear to exceed OEM specification
Designed for quiet, precise operation and straightforward setup
Backed by a 1-year warranty against manufacturer defects

Specifications

Differential: GM 12-bolt passenger car
Ratio: 3.90
Pinion spline count: 30
Ring gear bolts: 12
Ring gear diameter: 8.875"
Warranty: 1 year against manufacturer defects

Included Components

1x Ring gear
1x Pinion gear

Product Description

The Yukon ZG GM12P-390 is a high-performance ring & pinion gear set for the GM 12-bolt passenger car differential - widely regarded as the strongest live-axle rear end GM offered during its short 1964-1972 production run, and a favorite among Chevelle, Camaro, GTO, and full-size muscle car builders. At a 3.90 ratio, this set is a common choice for aggressive street or strip use where quick acceleration matters more than highway cruising RPM.

Built with a 30-spline pinion, 12 ring gear bolts, and an 8.875" ring gear diameter to match factory specifications, this set is engineered for quiet operation and straightforward setup. Because GM also built a separate, physically different "12-bolt truck" differential during the same years, confirming you have the passenger car version - identifiable by its oval-shaped differential cover - is an important step before ordering.

This is a gear set only, not a full install kit - it doesn't include the carrier bearings, pinion bearings, shims, or seals needed to complete a gear swap. Pair it with an appropriate master overhaul or bearing install kit for your specific application. Installation requires differential disassembly and proper backlash and pinion depth setup, so it's best handled by an experienced DIY installer or a differential shop.