Powerglide vs. TH350: Which automatic transmission should I choose?

There are a variety of different automatic transmissions, making it challenging to choose the one you want for your vehicle. In this review, we will be comparing Powerglide vs. TH350 automatic transmissions side by side. With the Information here, you should make a better decision on the right one for you.

Before you decide on the transmission to buy, learn the specifications and the suitable applications of each one of them. This review will also cover the structural difference, performance, applications, fuel economy, cost, and transmission fluid of the Powerglide and the TH350. An informed purchasing decision can save you time and a few dollars compared to just going to the market without prior knowledge of the products.

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Overview

TH350 Automatic Transmission

This is a three-speed transmission with a high reputation regarding performance and general build quality. It was introduced in the auto industry in 1969 as the successor of GM Powerglide automatic transmission. TH350 was a joint venture between Chevy and Buick, and the reason why it was also called (Chevy and Buick Combined) CBC 350.

The TH350 automatic transmission is 21.75 inches long and enclosed in an aluminum alloy one-piece case. It weighs 120lbs and features a distinctive oil pan located at the passenger side rear corner and a modulator at the right rear end of the casing.

Powerglide Automatic Transmission

Unlike TH350, which is a three-speed transmission, Powerglide is a two-speed transmission. This transmission was designed by General Motors and was targeting mainly the Chevrolet vehicle models from January 1950 all through 1973. Powerglide also dominated the Canadian market, where it was used on Pontiacs.

The two main types of Powerglide transmission include the Cast Iron Powerglide and Aluminum Powerglide. As the names suggest, these transmissions either had cast-iron or aluminum cases. There is also a third version of Powerglide called Torque-Drive, a semi-automatic transmission with no vacuum modulator. Drivers of cars with that transmission had to manually select gears as either high or low.

Powerglide vs. TH350

Specs

powerglide weight
Powerglide and TH350 have a handful of different features, e.g. the length, weight, speed, etc.

The length of Powerglide varies from 18 inches on a dragster-style Powerglide transmission to 28 inches. TH350, on the other hand, has different overall lengths depending on the size of the tail shaft. A 6-inch tail shaft TH350 is 27 11/16 inches long, and a 9-inch one is 30 11/16 inches long. The longest TH350 transmission is the 12-inch tail shaft one, which measures 33 27/32 inches in length.

The two gears in Powerglide limit its application. It is only preferred for use on cars with a very high horsepower to weight ratio. Powerglide is a relatively good choice for a vehicle weighing about 3400lbs and output engine power of not less than 1000hp. But still, you cannot have the best of both worlds when accelerating off the line and cruising at the highway speed.

TH350 has an aluminum alloy casing and weighs about 120 pounds. Powerglide is also enclosed in either aluminum or cast-iron casing and has a standard weight of between 100 and 120 pounds.

Powerglide is a two-speed transmission fitted with two different gear ratios, either 1.76:1 or 1.82:1. The 1.76:1 ratio is for high-performance vehicles and some trucks. As a result, the 1.82:1 became more common. TH350, on the other hand, is a three-speed transmission. It employs a deeper 2.52:1 first gear ratio that enhances initial acceleration compared to the Powerglide.

Structural difference

TH330 was introduced into the market to replace Powerglide. As a result, you can expect little to no structural difference between the two. They both have the bell shape and are almost the same size to make it easier to upgrade vehicles that use a Powerglide transmission.

Most users have stated that swapping Powerglide with TH350 is a straightforward process. The only modification you need to make is notching the cross-member front flange to accommodate the TH350 pan, which is the most evident structural difference. If installing either TH350 or Powerglide in a non-GM vehicle model, you will need to purchase a new adapter.

powerglide vs th350
The TH350 is slightly better than Powerglide in terms of fuel economy, but the determining factor would depend on the owner’s needs

Performance

The stage 1 TH350 is rated for up to 450hp. If you are looking for something stronger, you can go for the stage 2 variant with a horsepower rating of up to 550. You should also notice that the aftermarket price differs depending on the version of the two TH350 you choose, with stage 2 being the most expensive.

The performance of Powerglide also depends on the size and engine type of the car where it is installed. V8 engines come with a heavy-duty Powerglide. A transmission with a gear ratio of 1.76:1 can safely handle between 700-750hp, while the one with a 1.82:1 gear ratio can bear between 500 and 550hp. That means you can choose a Powerglide depending on the application. In general, the strongest OE-style Powerglide is the best option for a 750hp, 3,000-lb car.

Comparing the reaction time, Powerglide carries the day. A 3-speed TH350 will require more horsepower to get all the gears in motion. Additionally, the extra third gear creates drag and resistance that significantly affects accelerations. Powerglide is more efficient than THC350 because it only requires 18hp to set its internal components in motion, unlike the 44hp needed by TH350 to get all the gear sets in motion.

However, the performance will depend on the intended applications. Th350 is better in some situations than Powerglide. When looking for any of these vintage automatic transmissions, first consider the intended purpose.

Application

Powerglide is an ideal choice for quarter-mile cars or performance engines with high rpm limits. You can also consider them for street-worthy muscle cars with more engine power. An aluminum Powerglide that weighs about 100lbs is perfect for racing applications. Their lightweight and closeness to the drivetrain make it have a short reaction time. You can accelerate quite fast, reaching top speed in less time.

TH350 became an instant success in street performance and drag racing. However, it should be built correctly to handle high engine torques and tuned for more performance for the intended applications.

Fuel economy

Comparing Powerglide and TH350, the latter has more fuel economy, though the difference is not that significant. Arguably, the more gears you have, the more efficient your engine runs. The extra one offers better acceleration and improves fuel economy.

Low-gear transmissions such as TH350 and Powerglide are commonly used in drag cars. But on the highway, you might need high-transmission gears to save on fuel consumption. If you have to choose between the two automatic transmissions, TH350 would be the best option. It has three gears, as opposed to two on Powerglide. Powerglide is perfect for a high-torque engine car.

Cost

The cost of these automatic transmissions will vary considerably depending on the process. Most people prefer rebuilding them from donor cars to suit their needs. The prices also depend on what you want to do for a rebuild. Do you need an overhaul or just improvements? The cost can further increase depending on how much you will pay for your torque converter.

On average, it will cost you between $1,200 and $1,500 to rebuild a TH350 transmission. A Powerglide racing transmission can cost you between $2,000 and $8,000 without labor charges. Rebuilding will cost you about $500, depending on the upgrades you need if you have a mechanic.

Transparts Warehouse Powerglide Transmission Rebuild Kit

Transparts Warehouse Powerglide Transmission Rebuild Kit

Rating

Price range: $104-$124

Transparts Warehouse TH350 Transmission Rebuild Kit

Transparts Warehouse TH350 Transmission Rebuild Kit

Rating

Price range: $365-$375

Transmission fluid

Both Th350 and Powerglide use the same fluid. Ford fluid (type F) is recommended in all Powerglide or TH350 transmissions. Dexron VI is also a good transmission fluid for newer models of the TH350, while if you have an older TH350, Dexron III is a great choice.

Ford’s Type F Automatic Transmission Fluid – 32 oz

Ford's Type F Automatic Transmission Fluid - 32 oz

Rating

Price range: $8-$18

ACDelco Dexron VI Automatic Transmission Fluid – 128 oz

ACDelco Dexron VI Automatic Transmission Fluid - 128 oz

Rating

Price range: $25-$35

Triax DEX III/MERC Automatic Transmission Fluid – 128 oz

Triax DEX III/MERC Automatic Transmission Fluid - 128 oz

Rating

Price range: $20-$30

Conclusion

Powerglide and TH350 are excellent automatic transmissions for racers and streetcars. They deliver much power to the wheels while remaining fairly fuel-efficient. They are also available at the best prices in the aftermarket. You can also pull them off from donor vehicles in the garage and make necessary modifications to suit the application.

The transmissions have nearly the same features with few differences. However, if I have to recommend one, then I would go for TH350. It costs less to build and tune to meet different application requirements. TH350 is reliable, simple to repair, and stall converters are cost-effective.

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1 thought on “Powerglide vs. TH350: Which automatic transmission should I choose?”

  1. Thanks for sharing the great tips! Mr. Peterscott and I bought a new car at the request/suggestion of his dad.
    We paid it off 6 months later. But we have agreed to look at Used Car Engine first next time.

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