Home Cd converter Powerglide, Turbo 350 and Turbo 400

Powerglide, Turbo 350 and Turbo 400

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When repairing or restoring your Chevrolet car or truck, identifying the transmission you are using is a key part of avoiding the automotive version of quicksand. General Motors has produced a myriad of versions of its legendary automatic transmissions over the years, although three models make up the bulk of GM pre-ECM black transmissions; the Powerglide, the Turbo-Hydramatic 350 (Turbo 350) and the Turbo-Hydramatic 400 (Turbo 400). Let’s take a brief look at the backstory and origins of each transmission, and how you can visually identify them as well as locate ID tags and ID numbers.

The easiest method of identifying a GM automatic transmission is to examine the transmission case. The scalable designs have come with unique pan shapes, which are clear indicators of the drivetrain you are dealing with. Once you have identified the chainring, count the number of bolts in the chainring for confirmation.

GM has produced many drivetrain variations over the years, we’ve included some here, but our main focus is on identifying fluid sumps for Powerglide, Turbo 350, and Turbo 400.

The length of the unit can also tell you a few things. The diagram below is not only helpful for identification purposes, but it’s also a great visual source to see if you have enough room for a swap you might consider. For example, replacing a Powerglide with a Turbo 350 is an easy trade-in. This is because the transmission lengths are the same and the positioning of the crosshead can be easily changed, you just need to change the transmission medium, add transmission cooling lines and update the shift indicator. gear to a Turbo 350 model to complete the exchange.

The Turbo 400 is the biggest, the Turbo 350 and the Powerglide the smallest.

Never underestimate the mighty post-war Powerglide. This two-speed gearbox thrived after 71 years and is still used in motorsports and classic cars. There aren’t too many gearboxes that can make this claim. When introduced in higher-level Chevrolet models in 1950, the Powerglide represented the first automatic transmission offered by the Big Three. Ford didn’t offer its automatic transmission until 1951, and Mopar buyers had to wait until 1954.

The Powerglide was Chevrolet’s primary automatic transmission until the mid-1970s. A mechanically rugged transmission, it was also used in other General Motors vehicles. The transmission has undergone few changes, the main difference being the switch from cast iron to cast aluminum in 1963.

The powerful two-speed Powerglide

The Powerglide on the left is a cast-iron unit from a 1958-62 Chevrolet. The one on the right is a Powerglide with an aluminum housing.

In 1962, aluminum units were only used with the 327 engine, but by 1963 all Powerglides had aluminum housings. Corvettes from 1956 to 1962 only used the aluminum versions. Identifying a Powerglide involves locating the source code on the transmission block and decoding it to find the year the unit was manufactured and of course, the 13 bolt holes on the chainring.

Typical Powerglide Fluid Tray

Here’s what to look for:

  • Casting numbers on housing and expansion box.
  • Powerglide transmissions have been molded with the word Powerglide along the body
  • Date Cast Codes
  • Stamping of the assembly date code – can be stamped anywhere …
  • Chassis VIN number stamped or “source serial number” – from 1962

See the partial VIN stamped on the housing as well as the date code on the fluid sump.

Prior to 1967, transmission identification numbers contained the plant prefix code, month and date of production (expressed numerically), and a shift code (D = day, N = night). Beginning in 1967, the ID number contained the transmission type or factory prefix, the date (coded below), and a gearshift code. The transmission identification number decoding constants are the date the transmission was produced.

  • Example before 67: C213N – (C = Cleveland Powerglide, February 13, night shift)
  • Post-67 example: P9E03 – (P = TYPE, 9 = year (1969), E = month, 03 = day of the month)

The transmission identification number or source serial number (chassis VIN) is usually located near the transmission code. This number will contain a division identification number, model year, assembly plant and production sequence (the last six digits) of the vehicle identification number (VIN) stamped on the transmission.

A turbo of a 350

Responding to market demand for a three-speed automatic transmission, the Turbo-Hydramatic 350 was introduced in 1969 as a replacement for the Powerglide in Chevrolet cars and trucks equipped with six-cylinder or low-horsepower V8 engines. It is widely known as one of the best automatic transmissions ever made. Developed jointly by Chevy and Buick, it is also known as the CBC (Chevrolet-Buick Combined) 350.

The Turbo 350 quickly became known for its robustness, versatility and compactness. The Powerglide trailed as a low-budget automatic transmission option, but mostly behind six- and four-cylinder engines. In 1974, the two-speed gearbox then left for the big heap of junk in the sky. The Turbo 350 transmission was prevalent in almost all GM rear-wheel drive cars and trucks until 1984. It was phased out and replaced by GM’s 700R4 starting in 1982.

Typical Turbo 350 fluid pan. Remember to look for an almost square shape and 13 bolts.

Besides the shape of the fluid pan, another essential way to identify the Turbo 350 is the vacuum modulator. This modulator is placed on the side of the transmission and a vacuum line will be connected to it.

Some transmissions will have a code stamped on them while others have a label riveted to the case. Finding the ID tag can be extremely difficult on the Turbo 35o, especially since it has likely been lost. If it is still attached, the ID can be found in several places on the transmission:

  • Near where the shift linkage attaches to the body
  • Just above the housing on the right side of the pan
  • Passenger side on a flange by the bell

If you are under a car trying to read this it can be difficult. Not only will you need to research and hopefully find the label, but it should be free of enough grime to be readable.

Above is the transmission identification tag on a 1970 Corvette. Note the partial VIN stamped at the bottom.

You will need to decipher the numbers on the ID tag to tell exactly what type of transmission you have.

  • MV4 – This code identifies your turbo 350 as a “C” model, which had a lockable torque converter. This code was used for ten years from 1976 to 1986.
  • MX2 – Another 350C code. Found on ’76 thru ’84 models
  • MX3 – Another Turbo code 350 C. 1976 to 1981 model years.
  • MX5 – Turbo 350C, 1982 and 1983 only.
  • M33 – This standard Turbo 350 code identifies it as a standard Turbo 350. This version did not have a lock converter. Manufactured in ’76 until ’81.
  • M38 – Standard Turbo 350 manufactured from 1976 to 1981.

The Mac-Daddy 400

The Turbo 400 was GM’s heavy-duty three-speed transmission used from 1964 to 1990. It was standard equipment on large-displacement, high-torque engines, and is typically found in GM trucks and full rear-wheel drive cars. greatness.

The Turbo 400 has a very distinct fluid sump.

The 400 transmission has a 24-3 / 8 inch long cast aluminum alloy main housing. Its casing is essentially smooth. The shape of the fluid pan is irregular compared to the distorted borders of the state of Texas. It also uses the same vacuum modulator as the Turbo 350. The Turbo 400 is the largest of GM automatic transmissions, but is still surprisingly compact considering the immense power it can handle.

Another quick way to identify a Turbo 400 is to look at the downshift mechanism. Unlike the Turbo 350, instead of a “kick down” cable, it uses an electric slide switch, which is controlled by the throttle linkage. Usually, in vehicles from 68 to 71, the switch is located on the carburetor. On ’72 -’77 vehicles, the switch is located above the accelerator pedal.

The locations of the “kick down” switches for the Turbo 400

There are two important variants of the Turbo 400. The Turbo 375 was a version of the transmission used from 1972 to 1976, in small displacement cars. It is most easily identified by its designation “375-THM” molded into the underside of the tail housing. The Turbo 475 was an extra-heavy version and was found in large trucks starting in 1971.

In the early 1990s, GM renamed all of its transmissions. They created a standardized naming system for the entire product line and changed the name of the Turbo 400 to 3L80. The 700R4 became the 4L60 and so on. There is no difference other than the name. 3L80 means three speed, longitudinal mount (rear wheel drive), and the 80 means it can support 8,000 lbs. gross weight.

Steel label on passenger side:
CD-68-315953
(C: Chevrolet, D: 327, 68: 1968, 315953: sequential production number)

Serial number stamped on the housing, above the oil pan, driver’s side:
18L165790
(1: Chevrolet, 8: 1968, L: Van Nuys, CA, 165790: last 6 digits of the VIN)

The Turbo 400 transmissions had a partial VIN stamped either above the driver’s side panoramic rail (very difficult to see with the exhaust system installed) or on the driver’s side of the bell as shown in the photo.

Additional information on the serial number of the Turbo 350 and Turbo 400

On the Turbo 350, the VIN will be stamped either on the driver’s side housing (near the gear lever), on the right side of the housing just above the crankcase, or on a boss behind the flange of the passenger side bell housing. of transmission. On the Turbo 400, the VIN is stamped on a machined surface just above the driver’s side bin.

Prior to 1967, transmission identification numbers contained the factory prefix code, month and date of production (expressed numerically), and a shift code (D = day, N = night). Beginning in 1967, the ID number contained the transmission type or factory prefix, the date (coded below), and a gearshift code. The trans ID number decoding constants are the date the transmission was produced.

Example before 67: C213N – (C = Cleveland Powerglide, February 13, night shift)
Post-67 example: P9E03 – (P = TYPE, 9 = year (1969), E = month, 03 = day of the month)

Month code:
A = January, B = February, C = March, D = April, E = May, H = June, K = July, M = August, P = September, R = October, S = November, T = December


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