With its stacked headlights, split grill and a 14.5-second quarter mile from a standing start, the 1965 Pontiac GTO was sex on wheels. Its 389-cubic-inch V-8 came stock with a single, four-barrel carburetor, or an optional high-volume manifold topped by three, two-barrel carburetors that helped wrench 368 horsepower from an otherwise placid, 280-horsepower, family-car engine. Drivetrain options ranged from an automatic and a 3.08-to-1 rear end, to a close-ratio, four-on-the-floor and an optional limited-slip differential.
The 1965 GTO had five standard rear ends: 3.08-to-1, 3.23-to-1, 3.36-to-1, 3.55-to-1 and 3.90-to-1. Two limited slip differentials were available as dealer-installed options, one with 4.11-to-1 gear ratio and the other with a 4.33-to-1 ratio. Regardless of the gear ratio, you could top off the ’65 GTO’s differential case – the center housing, where the gears lived -- with two quarts of 80W-90 gear oil. Posi-Traction limited-slip differentials required the addition of a 4 oz. bottle of GM’s proprietary additive for limited-slip differentials.
