Th350 vs 700r4: which Transmission to chose?

Are Th350 and 700r4 interchangeable? There are a lot of questions that should cross your mind when you are trying to compare the TH350 vs 700r4 transmission. 

These transmissions are great products of General Motors. However, just as they have their similarities, there are also differences. 

From horsepower, weight, performance, and durability, there are specific reasons why you may prefer one over the other. When you want a transmission that can handle highway gears and offer a better gas mileage, which will you go for? TH350 or 700r4? Which is a better option?

Let’s take a deep dive into exploring the differences, similarities, and features that will help you choose between them.

Th350 vs 700r4 (side by side compression table)

HP500Hp650 – 1000Hp
Transmission3 Speed4 Speed
Gear RatioFirst Gear: 2.52 – 1.00
Second Gear: 1.52 – 1.00
Third Gear: 1.00 – 1
Reverse Gear: 2.07 – 1.00
First Gear – 3.06
Second Gear – 1.63
Third Gear – 1.00
Reverse Gear – 2.9
Bolt Pattern13 bolts16 bolts
Weight (without fluid)120 pounds155 pounds
Length (Inches)21 ¾23 3/8
Manufacturing Year19691982
OverdriveNo OverdriveOverdrive

difference between a TH350 and 700r4 (5 key Differences)

1. Design

Both the transmission come with designs and this might become the first thing you will notice about them. The TH350 transmissions feature a 13 bolts plane, with a five-shaped pan carved to the shape of a trapezium turned upside down. 

This is compared to the 700r4 which takes a longer shape than a rectangle. The 16 bolt 700r4 transmission with a varying length of 23 3/8 inches and a 155 pounds weight, making it heavier than the 120 pound Th350 transmission. 

Winner: 700r4

2. Overdrive

Th350 doesn’t have an overdrive. 700r4 comes with an overdrive. With an overdrive, the car’s engine can achieve a stipulated speed even at a lower RPM. 

This achieves fuel economy, a quiet ride, especially on the highway. Although the TH350 is a tough transmission with the ability to handle intense power and pressure needs, the absence of an overdrive puts it off a scale with 700r4. 

700r4 overdrive’s feature is fitted to the fourth gear offering a 30% increase. This process steps up the gear’s ratio, a better alternative to direct drive, in terms of handling long distances. 

With the Overdrive in 700r4, you can take up long rides. Unfortunately, it is not equipped with enough power to handle a ride uphill, towing, or a drag race.

Winner: 700r4

3. Operation

TH350 operates with a vacuum modulator and a kick-down cable. On the other hand, the 700r4 operates with a throttle valve (TV) cable and shift modulation operation. 

This makes it possible to run a 700r4 without a computer. This shifts operations in 700r4 to throttle positions, output shaft speed, and load. 

The TV modulates shift control and firmness. This is different from the vacuum modulator that is located in front of the right-hand side of the transmission (rear position).

Winner: Both

4. Usage

TH350 is the transmission for light-weight vehicles. With its low-torque transmission, compactness, and adaptability, it became the reliable choice for vehicles with a smaller internal space. 

700r4 is a better fit for heavy vehicles. This is because of its weight. More importantly, it is a perfect choice if your car is strictly for highway or long-distance rides. 

With a 700r4, you will find its lower first gear beneficial for takeoff. However, you should also consider that TH350 is a three-speed transmission while 700r4 is a four-speed transmission. 

This plays a huge role in determining the kind of cars that they are found in. 700r4 were majorly found in most rear-wheel-drive cars. 

The Chevys, Suburban, Camaro, Corvette, Astro Van, or any of the 1980’s cargo or custom van. Although TH350 was also found in rear-wheel-drive cars, they are peculiar to smaller cars such as Pontiac Firebirds, Chevrolet Camaros, and some GMC trucks.

Winner: 700r4 for a smaller internal space TH 350 better fit for heavy vehicles

5. Horsepower

Th350 handles a horsepower of 450 – 500Hp. This is compared to 700r4 which can handle a horsepower of 650Hp and after modifications, it can scale to 1000hp. This modification and upgrade will include the increase of its input shaft to accommodate a greater torque capacity.

Winner: 700r4

700r4 vs Th350 (key similarities)

1. Spline Count27- 3027- 30
2. Same Manufacturergeneral motorsgeneral motors
3. Turbo Hydramatic TechnologySameSame

1. Spline Count

The 27- 30 spline is the same in 700r4 and Th350. The similarity in the spline output shaft offers a fairground to easily swap a 700r4 with a Th350.

2. Same Manufacturer

Th350 and 700r4 are products of general motors. They follow the same technical build as automatic transmissions, but with upgrades that make each transmission suitable for a specific car need. 

They are both made of aluminum, although careful details are put into their production to achieve a variation in their material type. However, the concept behind remain the same; to introduce an automatic shift of gears.

The initiative grew from just automatic transmissions to integrating Hydramatic technology into their production.

3. Turbo Hydramatic Technology

The turbo hydramatic technology became the successor to hydramatic, dynaflow, Powerglide, jetaway, and super turbine 300 transmissions.

General Motors took a giant leap with 700r4 from the regular three-speed automatic transmission, to producing a four-speed automatic transmission. 

Although the initial rollout of the TH350 made it look like a three-speed Powerglide. With upgrades down to the TH350-C, it adopted the full mechanical process of a turbo hydramatic technology which 700r4 shares.

700r4 and th350: which one to chose?

If 700r4 and Th350 transmissions are as good as we have explained, which should you prefer? It boils down to why you need a transmission. 

If you will love a light transmission, with a better gear ratio and you will love to take them up for drag racing sometime, then you need a TH350.

But, you must understand that you are sacrificing the good gas mileage and overdrive that 700r4 offers. 700r4 is the best type of transmission for highway driving.

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People also ask

Will a 700R4 fit in place of a TH350?

The 700r4 was simply an upgrade of the Th350, with differences in size, structure, and shape. Without adjustments, a 700R4 will not fit in place of a TH350.  

However, it boils down to the drive shaft of your 700r4 and the TH350 that it should fit in its place. For a 700r4 to fit in place of a TH350, you must adjust (reduce) the driveshaft length, match tail shaft length, compromise TV cables, need for cross-member, torque arm mount, and a vacuum hose. For a 700R4 to fit in place of a TH350, the transmission must meet the conditions for a successful swap.

How much HP can a stock TH350 handle?

Stock TH350 can handle up to 450 – 500 hp. Adjustments to the gear ratios, gears, and torque output impacts the amount of Hp that a stock TH350 can handle. However, there are a lot of factors that could determine how much your rebuilt TH350 can handle.

You will achieve a great HP on a stock TH350 if you ride on street tires. You might consider installing a shift kit B & M for improved performance.

What does a shift kit do for a TH350?

A shift kit improves the shift performance in Th350. This is done by influencing an increase in the line pressure, increasing the volume and fluid substance in the clutch pack, and maintaining a perfect harmony in the timing of the shift, to reduce the number of overlaps and achieve a shorter and firmer shift.

Is TH350 and Turbo 350 the same?

Yes. TH350 and Turbo 350 are the same. The TH350 transmission is part of the family of Turbo Hydramatics. The TH350 is part of the development of GM motors, a trade name for a family of automatic transmissions. Each brand of Turbo automatic transmission comes with the 

Each brand of automatic transmission in the turbo hydramatic family comes with an attached ‘TH’ to its brand number. This indicates its model and class. The TH350 is the same as the Turbo Hydramatic 350.

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closing thoughts

Choosing between Th350 Vs 700r4 boils down to what you are expecting from a transmission. You can decide to forfeit the benefits of fuel economy, for a less expensive transmission with a better first gear.

More importantly, your budget should play a great role in determining which of these transmissions is the best choice for you.

We believe that this review will give you the required information to make a good choice and better market decisions.

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Mahir Ahmed


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