19673-010 POSI 8.5 GM 17 SPL 4.11/4.56 RATIO 1963-1979

Product Details

Eaton Posi
High performance limited-slip differential

Originally released for General Motors’ Chevrolet Truck Division in 1959, the Eaton Posi limited-slip
differential (then “Eaton Trac-Aide” and branded by GM as “Posi traction”) is designed to provide significantly
enhanced traction capability for a wide variety of vehicles. The original units were strictly designed for
enhanced traction. In the fall of 1959, following the results of extensive testing by GM’s Cadillac Motor
Division, the design was revised to provide a higher and more consistent bias ratio with reduced “chatter.”
Since those early days, many improvements and innovations have resulted in the Eaton Posi becoming
the industry leader for high performance clutch-style limited-slip differentials.
In addition to 60 years of product engineering and testing, Eaton proprietary clutch materials, industry
leading gear strength, and advanced manufacturing processes have allowed the Eaton Posi to continue to
lead the way in affordable performance enhancement.
All Eaton Posi designs are subjected to rigorous validation tests at our Michigan-based 700 acre
proving grounds and dynamometer facilities for validating strength, durability, performance, quality
and torque capacity.
The Eaton Posi has two distinct characteristics. For low torque conditions, the preload springs apply an initial
resistance by energizing the clamp load of the clutch
packs. The product design allows for different spring loads to be swapped into the differential to increase or
decrease this initial bias ratio/torque transfer capability. Spring loads are often used to “tune” the handling
dynamics of performance vehicles. The spring cage design also ensures this load is perfectly balanced
between sides and evenly distributed to the clutch surfaces. Once additional torque is applied, the gear
tooth design becomes the dominant force generator to the clutch packs. The torque is used to separate the
side gears from the pinion gears, providing increasing resistance in the clutches. This resistance does two
things: slows the low-traction wheel and diverts power to the wheel most able to put the power effectively to
the ground.

• Fits 4.10-4.56 Gear Ratio 
• Fits 1963-1979 Corvette with 17 Spline Axles