Pontiac Powerglides

(GM Powerglide Automatic Transmission with BOP bellhousing bolt pattern)

The Powerglide is a two-speed automatic transmission designed by General Motors. It was available primarily on Chevrolet from January 1950 through 1973.

There has been a lot of discussion over the years involving Chevy’s Powerglide usage in Pontiac’s. Many are quick to correct others and tell them that they have the ST-300 (Super Turbine 300), and not a Powerglide. And in many, if not most cases, they are probably correct.

However, General Motors DID put the Powerglide in some Pontiac’s.

August 1953 Hydra-Matic Assembly Plant Fire:

A massive fire destroyed GM’s HydraMatic plant in Livonia, Michigan on August 12, 1953. As a result, Pontiac used Chevrolet’s Powerglide to complete that year’s model year production. About nine weeks after the Livonia fire, GM opened up a new source for Hydra-Matic production at Willow Run, Michigan. By the time the 1954 models debuted in late 1953, Hydra-Matic production had returned to normal levels and all 1954 model Pontiac’s with automatic transmissions were once again equipped with Hydra-Matics.

1964 – 1965 Pontiac Tempest:

The 1964 – 1965 Pontiac Tempest was produced with a 215 cu in overhead valve straight-6 engine, but it was not an original Pontiac design. Sometimes confused with the Buick designed and built 215 cu. in. aluminum V8 that Pontiac had used in the two years prior, the “Pontiac 215″ was an adaptation of Chevrolet’s 230 cu in overhead valve Generation 3 straight-6. Quite different from Pontiac’s previous straight-6s, it had a smaller bore (3.75”) than the 15 cu. in. larger Chevrolet engine and a Chevrolet bellhousing, but its flywheel/flexplate bolt pattern was Pontiac’s.

From 1964-1965, the 216 cu in engine was available with the Powerglide 2-speed transmission, since the Super Turbine 300 (ST-300) would not bolt to the Chevrolet bellhousing bolt pattern.

In 1966, the 6-cylinder was changed to Pontiac’s all new 230 cu in overhead cam. These Tempest models came with Pontiac’s Super Turbine 300 (ST-300) 2-speed transmissions.

If you look at the photos below of the Pontiac 215, you’ll see that it does in fact have a Chevy bellhousing bolt pattern as compared to the diagram in the bottom photo.

Canadian Cars:

Powerglides were used extensively on Pontiac’s produced for the Canadian market with Chevrolet powertrains. But it appears that the Powerglide usage went beyond the Chevrolet engines.

The image below is part of a sales brochure for a 1971 Pontiac Lemans:

Here’s the whole brochure page. Click the image to enlarge:

If you look in the bottom box, you’ll see that the 250 6-cylinder and 350 V-8 were optioned with a 2-speed Automatic. Pontiac stopped using the 2-speed ST-300 after 1969, and replaced its use with the Turbo Hydra-Matic 400, and Turbo Hydra-Matic 350. The only 2-speed available was the Chevy Powerglide.

The Powerglide pictured above was reportedly taken off of an early (1970-1972) Pontiac Firebird. You can see that it has the Buick-Oldsmobile-Pontiac bellhousing bolt pattern.

The Chevy Powerglide has been reportedly found on:

  • 1971 Pontiac Lemans with a 350
  • 1971 Pontiac Tempest
  • 1968 Pontiac with a 230 cu in straight 6
  • Early 2nd Generation Firebird (1970-1972)

The Chevy Powerglide was made from 1950-1973. If you you have a Pontiac with a 2-speed transmission, and a speedometer  that reads KM/H instead of MPH, you’re probably sitting on top of a Powerglide.

Super Turbine 300 (ST-300) -vs- Chevy Powerglide Comparisons:

Above is a Super Turbine 300 (ST-300) on the left, and a Powerglide removed from an early 2nd Generation Pontiac Firebird. Note that the Powerglide appears to have a dual pattern bellhousing, but is only drilled out for the Buick-Oldsmobile-Pontiac (BOP) bellhousing bolt pattern.

You can see that the Powerglide has a triangular servo, and that the ST-300 has a round servo. Also, you see that the vacuum modulator on the ST-300 is on the passenger side.

The photo above is of a normal Chevy Powerglide. Notice the difference between the normal Chevy bellhousing compared to the bellhousing  on the Powerglide removed from the Firebird.

In the photo below, you can see that the vacuum modulator on the Powerglide is on the drivers side, as well as other visual differences/

Chevy Powerglides With Dual Pattern Bellhousing Bolt Patterns:

The Powerglide has been made with the dual pattern bellhousing bolt patterns so that it can be bolted to Buick, Oldsmobile and Pontiac. Not all of these cases had the ‘Chevy’ holes drilled all the way through. These cases are rare, but they do exist.

See the photos below for more examples. The BOP Powerglide with the metal shield on it was listed on ebay in June 2017.

More Photos:

Click the photos to enlarge.