Q: I own a 1966 Pontiac GTO post coupe with a 389 cubic inch engine and a three-speed standard transmission.
How many body styles were available, and I am told the 3-speed manual in my car was made by Ford Motor Company and used at the end of the model run because GM ran out of 4-speeds. Is this true? M.M., Pennsylvania.
A: GM never ran out of four speeds, yet the transmission in your car is indeed a Ford designed unit.
Let's start with the body. In 1966, three body styles were offered, including a hardtop, which had no post between the side windows; the sport coupe, which did have a post; and a convertible.
The 1966 GTO's standard features include bucket seats, special exterior trim, 335-hp, 389-inch engine, 4-barrel engine with chrome valve covers and air cleaner, dual exhausts, and that 3-speed manual transmission you speak of.
If you wanted a four-speed, it was an option, as was the popular Tri-power 3-2-barrel setup. The pillared sport coupe had a retail of just $2,783, back then, which was quite a deal.
According to my records, the standard 3-Speed Manual Floor Shift in your GTO is called a Dearborn M13 unit. The four speeds available in '66 were a Muncie M20 and a Muncie M21 close ratio. Automatic fans had the Turbo Hydramatic M40 option, which would become known later as the Turbo 400.
The GM 3-speeds were produced by Saginaw, and also known as Muncie units. However, these 3-speeds didn't stand up well to the horsepower and torque of the GTO V-8 engines, so whoever told you that a Ford transmission is in your GTO from the factory is telling the truth.
GM chose this "Dearborn M13" Ford transmission to better handle the power, and from what I've seen "FoMoCo" is stamped right on the transmission case. Muncie/Saginaw 3-speed manuals were used in light duty units like 6-cylinders and small V8's. The GTO would use the Dearborn M13 for many years to follow.
By 1968, Muncie built its "rock crusher" M22, which could stand up to 500 horsepower and was a great tranny. On a final note, not many 3-speed GTO's are around, as most of the people would spend the extra money for the four-speed.
Congrats, as you have a rare GTO.