Upgrade Your Ride: The Benefits of 4-Speed with Overdrive Transmission

History of Overdrive

The use of overdrive technology in cars dates back to the mid-20th century when American cars with three and four-speed manual transmissions were introduced. Since the engines of these cars were not efficient at low speeds, drivers faced difficulties while cruising on the highways. Vance Heater, a transmission engineer, developed an add-on overdrive unit in the 1930s which helped the cars to perform better at higher speeds without consuming more fuel.

In the 1950s, American car manufacturers began to offer overdrive as a standard or optional feature in their vehicles. Cars with overdrive had an additional gear that reduced the engine speed and saved fuel, making them more efficient at cruising speeds. Add-on overdrive boxes were also commonly available during this time, and people could install them in cars that didn’t come with an overdrive option.

YearManufacturerModelOverdrive Option
1955ChevroletBel AirOptional
1963FordGalaxie 500Standard

Overdrive technology became increasingly popular in European cars with manual transmissions during the 1960s and 70s. Edgar de Normanville, a British engineer, invented an overdrive unit for cars in 1934, and his design was later manufactured by Laycock Engineering. They produced over three and a half million overdrive units in several variations, and more than one million of these were fitted to Volvo cars.

The popularity of overdrive technology faded in the 1980s when car manufacturers began to replace manual transmissions with automatic transmissions. However, overdrive is still utilized in some modern cars as a gear that lowers engine speed and provides better fuel economy.

Benefits of Overdrive

Overdrive is a transmission gear that provides faster output shaft speed than the input speed of the engine’s input shaft. It operates when a car is cruising at a sustained speed with reduced engine RPM, resulting in better fuel consumption, lower noise, and lower wear. Here are some of the benefits of overdrive:

  • Fuel Savings: One of the main advantages of overdrive is the fuel savings it offers. When you drive at high speeds, using overdrive can reduce engine RPM, reducing the amount of fuel used. This can lead to significant savings, particularly if you do a lot of highway driving.
  • Less Wear on the Engine: Overdrive can also help to reduce wear on your car’s engine. When you use overdrive, the engine doesn’t have to work as hard, reducing the risk of problems with components like the spark plugs or piston rings.
  • Reduced Engine Noise: Overdrive gear can make your car quieter when driving at high speeds. By reducing engine RPM, overdrive reduces the noise made by the engine. This can make for a more comfortable and peaceful driving experience.

It’s important to note that choosing the right car for you is a subjective matter. You should base your decision on personal preference, location, and weather concerns. However, when it comes to choosing a car that maximizes fuel efficiency, overdrive can play an important role.

It’s also worth noting that overdrive was added to transmissions as a fuel-saving measure. The ability to reduce engine RPM while cruising was a tremendous advantage as it helps to reduce engine wear and save fuel. However, as transmission technology expanded to five and six-speed gearboxes, the addition of an overdrive system began to fall away in popularity.

Types of Overdrive

Overdrive is a term used for a gear that allows for faster cruising speeds, and better fuel economy. In this section, we will explore the different types of overdrive and how they work.

TH700R-4 Overdrive

The TH700R-4 is an overdrive automatic transmission used in General Motors (GM) cars and trucks. This type of transmission can shift into overdrive mode after a certain speed is reached and shift back to direct drive when more load is present. Switching it off can help with engine braking or when driving uphill or towing a trailer.

Gear Vendors Overdrive

Gear Vendors is a company that provides auxiliary overdrive units that can be installed on existing transmissions. This results in faster cruising speeds and better fuel economy by adding an additional gear reduction system made up of a combination of sun, planetary, and rings gears.

Planetary Overdrive

A planetary overdrive is a type of transmission that uses a planetary gear system to achieve overdrive. This gear reduction system is made up of multiple sets of gears, including a sun gear, a planet carrier, and a ring gear.

Electronic Overdrive

Electronic overdrive is a system that uses electronic controls to shift into overdrive mode. This type of system can provide better fuel economy and smoother gear shifts. Electronic overdrive is most commonly found in modern vehicles.

Direct Drive vs. Overdrive

Direct drive is a gear ratio in which the input and output shafts rotate at the same speed. Overdrive refers to a gear ratio in which the output shaft rotates faster than the input shaft. Overdrive is used to allow for higher speeds and better fuel economy, while direct drive is used for better power and acceleration.

TH700R-4 and its Usage:

The TH700R-4 is a type of automatic transmission that was first used in GM cars and trucks in 1982. It is an overdrive transmission, which means that it has a fifth gear that provides increased fuel efficiency at high speeds. Here are some important facts about the TH700R-4:

  • Designation: The TH700R-4 was originally designated as a Hydra-Matic MD-8 transmission according to GM’s RPO codes.
  • Length: Both the TH700R-4 and 4L60 versions have an overall length of 30 3/4 inches, except in the Corvettes, which measure 29 7/8 inches overall.
  • Compatibility: The TH700R-4 can be installed in place of the TH350 or TH400, but it may require modification to the driveshaft and crossmember.
  • Carburetors: The TH700R-4 is compatible with various carburetors, but it may require a TV cable connector kit and universal adjustable detent cable for proper length.

If you are considering installing a TH700R-4 transmission in your vehicle, it is important to understand its features and requirements. Here is a closer look at some of the key points above:


The designation of the TH700R-4 as a Hydra-Matic MD-8 transmission is significant because it reflects the fact that it was the first overdrive automatic transmission used in GM cars and trucks. This designation highlights the advanced design and technology of the TH700R-4.


The length of the TH700R-4 and 4L60 versions is an important consideration when planning a transmission swap. The overall lengths of 30 3/4 inches make the TH700R-4 slightly longer than the TH350 and TH400 transmissions. However, with the proper adjustments to the driveshaft and crossmember, the TH700R-4 can be installed in place of these earlier transmissions.


The TH700R-4 is compatible with a range of carburetors, but it is important to ensure that the proper TV cable connector kit and universal adjustable detent cable are used to achieve the proper length. Failing to use the appropriate kit and cable can result in poor shifting and potential transmission damage.

Gear Vendors Overdrive

If you’re looking for a way to improve your vehicle’s fuel economy while also increasing your cruising speed, look no further than Gear Vendors Overdrive. Here are some key facts to know about this innovative product:

  • Gear Vendors Overdrive is a planetary overdrive that is designed to fit most transmissions.
  • With Gear Vendors, you’ll be able to shift gears without using the clutch. This can make driving smoother and more enjoyable.
  • Performance Automotive and Transmission Center in Bossier, Louisiana, offers an adapter to fit the TH700R- 4 or 4L60 to B.O.P block bolt patterns. This means that you can easily install Gear Vendors in your own vehicle.
  • If you’re not completely satisfied with your Gear Vendors Overdrive, you can return it within 30 days for a full refund.
  • Gear Vendors also offers an impressive 2-year unlimited mileage, horsepower, and abuse warranty.
  • Gear Vendors Overdrive owes much of its success to the Muncie close ratio trans, which it was originally designed to work with.

As you can see, Gear Vendors is a powerful tool for improving your vehicle’s performance and fuel efficiency. With effortless clutchless shifting and a solid warranty, it’s a product you can rely on.

Conversion and Modification

If you’re looking to upgrade your Mopar A-833 manual transmission, Passon Performance offers an excellent solution with their unique overdrive gearset. With this retrofit, you can easily enhance the performance of your transmission and enjoy a more efficient and smoother driving experience.

The Passon Hemi Overdrive kit provides a street-friendly ratio spread, making it feel natural and progressive. What’s more, this kit comes with detailed step-by-step instructions, ensuring that you don’t have to worry about complicated modifications.

Converting a 4-speed transmission to a 6-speed is also possible, but it may not be the most cost-effective option. The Passon gearset is a great choice for those looking to update their transmission without breaking the bank.

With this overdrive gearset, you can look forward to improved fuel efficiency and reduced wear and tear on your transmission. Passon Performance is committed to providing the best possible solution for your transmission needs, and their overdrive gearset is no exception.

Interesting Facts related to Overdrive

If you own a car, you may have heard about overdrive, which is an additional gear in the transmission system. Here are some interesting facts related to overdrive:

  • Virtually all vehicles today come equipped with overdrive as an extra gear. This allows for more fuel-efficient driving on highways and reduces engine RPM, making for quieter and smoother rides.
  • The output of the transmission turns faster than the engine in overdrive, helping to save gas and reducing engine wear.
  • Overdrive via a four-, five-, six-, or even eight-speed transmission can solve this problem. More modern vehicles now come with six- and eight-speed transmissions to provide even greater fuel efficiency.
  • Overdrive systems are generally actuated by using a mechanical linkage or electronic solenoid. Heavier vehicles such as trucks require solenoid systems whereas smaller cars like sedans could use either type of actuator.
  • The use of overdrive should be done at appropriate speeds to keep the engine in peak efficiency range and to prevent wear and tear on the drivetrain. Generally, you should engage the overdrive once you reach a steady highway speed, usually between 45 and 60 miles an hour.

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