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TH350 Vs TH400

Difference Between TH350 and TH400

A turbocharger is one of the indispensable engines for car users. However, understanding the functions and usage of this machine is something that not everyone can do. Moreover, there are many different types on the market today.

However, this article will cover the two most common types, TH350 and TH400, and their similarities and differences:

What Is Turbo?

Before we get into the specifics of the th350 and th400, let’s take a look at the basics of Turbo. Basically, Turbo is a form of an air pump with the critical task of pushing more oxygen into the engine when needed.

As a result, if you need to burn more fuel to increase engine horsepower, Turbo will give you up to 50% more power to the engine.

Usually, a turbo will have two main parts: a turbine and a compressor. The turbine can spin at nearly 150,000 revolutions at about 30 times the engine speed by being directly connected to the exhaust stream.

Next, the compressor will use its fan to suck in the fresh air and pressurize the engine.

In general, the turbocharger plays an essential role in the engine system, intending to generate more power through forced induction…

Features of TH 350

TH 350 full name is General Motors Turbo Hydra-Matic 350. In 1969, TH350 first appeared on the market as a three-speed automatic transmission. However, it was later improved and replaced by a two-speed gearbox.

Later, when it was more developed, especially in 1986, Turbo 350 was favored by many manufacturers to be used in GMC and Chevrolet pickup trucks.

Basically, TH350 will weigh about 120 lbs and is quite suitable for use on small and medium vehicles.

In addition, TH 350 has a few basic features that any user should know:

The 350 TH is shorter and more adaptable on smaller-bodied cars.

With a lightweight aluminum body design, the TH350 will start at around 35hp and max out at 400hp. In addition, the TH350’s vacuum modulator will be mounted just behind the correct valve body. Besides, its plug will connect to the four wires on the left side.

Features of TH400

Compared to the TH350, the TH400 was introduced by General Motors earlier, in 1964. TH400 is a three-speed automatic transmission located in a vertical position just behind the engine.

Basically, this type of positioning has the role of providing the best ratio of power as well as durability to your vehicle.

Overall, the TH400 will weigh in at about 135 pounds without fuel with its aluminum and iron construction. It is also suitable for any transmission fluid color.

And yet, the TH400 comes with three tail shaft lengths and uses Amsoil fuel.

Difference Between TH350 and TH400

TH350 vs TH400

Having followed the TH350 and TH400 characteristics, you may have noticed some differences between the two turbos. However, the following are the primary and most specific differences between TH350 and TH400:

Gearbox shape: the most noticeable difference between these two turbos is that the TH350 will have a low-torque gearbox, and the TH400 will have a higher-torque transmission.

Thanks to this shape, the type of vehicle suitable for every kind of Turbo is also different. Usually, heavy vehicles will use TH350, and TH400 will be ideal for lighter vehicles.

Vacuum modulator position: typically, TH400 will be located on the right rear of the gearbox, and vice versa TH350 will be located in front on the same side.

Design: TH350 will have a square format and have a corner cut. With TH400, there will be a “hump” face in the pan and a curved side in.

Overall dimensions: TH350 measures approximately 33 inches in length and 21 ⅝ inches in body length. However, TH400 will be slightly better, about 38 inches in total length and 25 inches in body length.

How To Distinguish TH350 And TH400

As mentioned before about the typical differences between the two turbo types discussed above, it is sometimes tough to tell them apart.

However, do not worry too much because when you apply the following ways, you will quickly distinguish these two types of Turbo:

Locate the controller: First and foremost, locate the vacuum modulator. You will quickly see that the TH350’s modulator will be found in the front right of the transmission and has an additional kick-down cable. With the TH400, it’s still on the same side as the TH350, but it’s located behind the information.

Observe the moving pan: Both movable pans have 13 bolts. However, their shape is markedly different. If the TH350 has a square pan with an angle, TH400 has an oblong pan with one side with a “hump” in the pan and the other curved. And yet, the different two sides of the TH400 are quite straight, and its pan also has two circular depressions on the hump side of the pan.

Measure overall dimensions: the absolute difference that makes it easier to distinguish these two turbos is the overall size. The TH350 has a tail shaft length ranging from 7 inches to 12 inches, while the TH400 has a smaller length of about 5 inches to 13 inches. Besides, the size of these two turbos also has a slight difference; TH350 33 ⅝ inch and TH400 38 inch.


Some questions we regularly receive from customers that you may also be interested in:

Which is better: Turbo 350 or Turbo 400?

In fact, comparing these two turbos is often quite tricky. If the turbo 350 works exceptionally well with low-powered cars, the Turbo 400 is more durable and better equipped for high-performance cars. In general, all choices and decisions are up to you.

How much horsepower can a Turbo 350 handle?

Usually, TH350 will have a capacity of up to 450 horsepower in the first stage. However, if you are looking for something more powerful, you can go for the PN PA35102 version with up to 550 horsepower for approximately $1,200-1500.

Are all Turbo 400 the same?

In general, the Turbo 400 types are completely interchangeable when in the exact vehicle. Usually, though, you’ll find it on larger engines with more reliable performance.


Finally, before ending, hopefully, the information mentioned earlier can help you soon distinguish the difference between TH350 and TH400.

In general, when it comes to car engines, we get a lot of questions from users. Besides turbo issues, one of the related problems that many users wonder about is the problem of stopping a transmission leak.

So, if you have any questions or concerns, leave a comment and we will soon send you the most appropriate answer.

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