Eaton 913A555 Detroit Truetrac 30-Spline Limited Slip Differential for 1964-1972

Regular price: $716.99
Regular price: ~~$779.34~~
Sale price: $716.99

Shipping calculated at checkout.

In Stock: 0

Orders by 1pm PST ship same business day

Free Shipping w/3-4 Day Delivery

Authorized Dealer

Fitment Guarantee

30-Day Hassle Free Returns

Product Specification:

SKU:EAT913A555

MPN: 913A555

Weight: 27.4 lb

Type: Differentials

Vehicle Fitment

1964-1972 General Motors Chevrolet / Pontiac / Buick / Oldsmobile - 12-Bolt Car Rear Axle (Series-3 Carrier, 30-Spline, 8.875" ring gear)

Fitment Notes

Only fits GM 12-bolt passenger car rear ends with 30-spline axle shafts and 8.875" ring gear diameter
Ring gear bolts must be 9/16" head size or smaller
Axles must be cut with 45-degree pressure angles
Does **not** fit trucks/SUVs with larger carrier breaks or incompatible housing designs

Features

Helical-gear design delivers smooth, automatic engagement under power without clutches or wearable plates
True limited-slip performance (LSD) for improved traction in both forward/reverse
Maintenance-free operation - sealed unit requires no periodic friction modifier or service of internal parts
Wide gear ratio compatibility (3.08:1 to 3.90:1) supports a variety of driving styles
Heavy-duty build using steel carrier and durable components for long life under street and performance use
Quiet operation due to helical cut gears, less noise compared to traditional clutch-type LSDs
Optimized for street muscle, drag, and restoration use, while also handling moderate off-road or towing stress
Direct bolt-in fit for applicable GM 12-bolt housing - no major modification required other than verifying bolt and pressure-angle specs

Specifications

Ring gear size: **8.875 in (GM 12-Bolt Car Rear)**
Axle shaft spline count: **30 splines**
Axle shaft diameter: **1.29 in**
Permitted ring & pinion gear ratios: **3.08 - 3.90**
Carrier: GM Series-3 / "12-Bolt Car" carrier type
Cover bolt count: 12 bolts
Pressure angle: 45-degree pressure angle gears required
Designed weight; approx. 27 lb gross unit weight

Included Components

1x Eaton Detroit Truetrac differential carrier assembly (part # 913A555)

Product Description

The **Eaton 913A555 Detroit Truetrac** is a helical-gear limited-slip differential designed specifically for GM 12-bolt rear car axles dating 1964-1972. Engineered to fit 8.875" ring gear housings with 30-spline axle shafts, this differential transforms traction, improving throttle response, handling in slippery conditions, and overall stability during acceleration without the drawbacks of clutch-type LSDs.

Inside, pairs of helical gears automatically transfer torque to the wheel with greatest grip, while remaining open under light loads for smooth, quiet turning. With permitted gear ratios from **3.08:1 to 3.90:1**, it gives flexibility so you can maintain factory gearing or upgrade for performance. The unit is sealed and requires **GL-5 mineral-based 80W-90 gear oil**, with no synthetic restrictive requirements or friction modifiers. Pressure-angle matching (45°) and proper ring-gear bolt head size (≤ 9/16") are essential to ensure fitment and avoid mechanical conflict.