Yukon Gear & Axle

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

Add to cart

 

 

Product Specification:

SKU:YUKZG GM12P-390

MPN: ZG GM12P-390

UPC: 883584361695

Weight: 16.5 lb

Inventory: 2

Type: Final Drive Gears

Description

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.