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Monthly Archives

May 2020

Why Are 700R4 Torque Converters The First Choice In The Market?


Choosing the right torque converter for your vehicle can be tricky. You need to weigh in a plethora of factors for getting noticeable improvement in the acceleration capabilities of your vehicle. Regardless of whether you are a street driver or an enthusiastic car racer, you need to follow some basic guidelines for ensuring your car performs to its true potential. This primarily includes the stall speed, power curve, and torque output of the vehicle.

Most modern users opt for 700R4 or the 4L60E torque converters while upgrading to an overdrive automatic. This is due to the fact that both of them are sophisticated solutions and offer ample convenience. However, they mainly differ in terms of their electronic circuitry. Here are a few parameters that give an edge to 700R4 torque converters:


Most overdrive rebuilding options come at a heavy price. If you are planning to upgrade your transmission system, you should consider going for analog overdrive versions. This will allow you to enjoy the benefits at a lower price.


Unlike 4L60E torque converters, 700R4 can be installed without any hassles. All you have to do is to take care of the TV cable hookup, shorten the driveshaft, move the cross-member, and add a 12-volt source to the transmission.

Simple Conversion

Since 700R4 comes with an old-school speedometer cable, it is much easier to handle. You can upgrade any old chassis by following some minor floor pan tweaking procedures.

When it comes to transmission systems, Gearstar Performance Transmissions has it all covered. Get in touch with them to buy 700r4 torque converter lockup kits for your vehicle.

TH350 Transmission Identification, Decoding and Super-Tuning

TH350 Transmission Identification, Decoding and Super-Tuning - Gearstar Performance Transmissions

The TH350 (Turbo-Hydramatic) transmission identification, decoding, and super-tuning are what sets it apart from other transmissions. Its identification, for instance, helps you to differentiate this one-piece unit from other transmissions launched by General Motors.

And the super-tuning of this unit ensures that you can improve its performance to be a ride worth taking on fast and hard spins. Now this and many more are what we’ve outlined below. Therefore, work with us let’s show you all you need to know about this unit.

TH350 Transmissions 101

The TH350 transmission is a three-speed automatic transmission launched by General Motors in vehicles from 1968. It can also be said this model was created as a collaboration between Chevrolet and Buick, where the transmission was made to be compact, strong, and versatile.

On the other hand, the TH350 was to serve as a replacement to the Powerglide transmission, which is a two-speed automatic transmission. Cars that used the TH350 transmission include those from the late 1960s, as well as some GM all rear-wheel-drive vehicles launched in 1984.

The transmission model was used in these cars until the early 1980s when the 700R4 transmission was launched. That being said, chances that you’re using a GM vehicle with the TH350 transmission are high if the car is a model launched around these years.

TH350 Transmission Identification

The TH350 transmission is 21-3/4″ long and its body is made of aluminum alloy. The unit comes with a bell housing and weighs 120 lbs. Here is a list of steps that will help you to identify the TH350 transmission:

1. Set Up the Wheel Chocks

Adjust the wheel chocks at the back of the tires to ensure that the vehicle is firmly rooted to the ground. Use your jack to lift the vehicle slightly while also ensuring that the jack sits securely beneath the frame rails.

You can then lower the car onto the stands. Slide beneath the vehicle and find the transmission. This transmission is mostly stationed at the rear-wheel of cars hence, its location may be the same in yours.

2. Count the Number of Bolts

Ascertain the number of bolts that are secured to the transmission oil pan. And if the number of bolts is around 13, then it means the unit is either a TH350 or TH400. On the other hand, the transmission oil pan is usually bolted to the transmission bottom.

However, you can tell if it is a TH350 or TH400 depending on the transmission oil pan’s shape. If the pan is square in shape and looks five-sided due to a cut in one corner, then you are dealing with the TH350.

3. Check the Length of the Transmission

It is also important to measure the length of the transmission. This measurement should be taken from the front and from where it bolts to the back of the engine to the transmission’s end that links the tailshaft housing.

On the other hand, there’s no need to measure the tailshaft housing and this is an adapter with a cone-shape design. It is worth noting that the length may range from 22 ¼ to 22 ¾ inches if it is the TH350 transmission.

4. Find the Vacuum Modulator

The next step is to find the vacuum modulator. This modulator has been stationed at the transmission’s side and there may be a rubber vacuum line connected to it. You’ll know it’s the TH350 if you have the fitting attached to the right frontal side of the transmission. However, it is the TH400 if this fitting is at the transmission’s front-rear side.

5. Check the Connection

There’s a cable that may be connected to the transmission’s side and next to the location of the shifter linkage. In this case, you are to ascertain if the cable is connected to the engine. The cable is a kick-down cable and the TH350 has this cable whereas the TH400 does not have this feature.

TH350 Decoding

One more thing you can fall back on to identify the TH350 is the stampings placed on the transmission’s side. The part codes that may be evident include the M33, M38 & M39 and these codes were for the conventional TH350.

On the contrary, the TH350C, a variant of the TH350 that has a lock-up torque converter had codes including MV4, MX2, MX3 & MX5. Asides from this, other variants of the TH350 were launched and these are the TH200, TH200C, TH250, TH250C and TH375.

TH350 Super-Tuning

Super-tuning the TH350 transmission involves modifying the stock transmission to ensure it is suited for street or strip use. The stock transmission may be able to withstand the impact but only to a certain degree, which brings about the need for super tuning to handle high-performance applications.

And using this transmission comes with an advantage since many car enthusiasts believe that out of all GM transmissions, it is the budget high-performance automatic ride. Therefore, you can carry out inexpensive changes to this transmission even without taking it out of the car. Here’s what you need to begin:

1. Modifications to Certain Components

Changes in components like the governor alterations, valve body recalibration, and modulator swaps can improve the TH350 transmission. By improvement, you can expect enhanced shift timing. These modifications can be made without removing the transmission from the car.

2. Upgrades

Specific upgrades are needed if your transmission will be used in applications that transmit 400 lbs-ft of torque or higher through the transmission. The limit will be dependent on the vehicle’s gear ratio, weight, driving style, and even traction.

3. Other Minor Upgrades

A TH350 rebuilt is not complete unless you have a high-performance clutches and even reducing the friction. This setup will enable the transmission to send more power to the wheels, which could also increase durability.

And if you’re wondering how you’ll reduce the unit’s friction, you can start by using needle roller bearings. These bearings can be used at the front planetary pinion carrier as well as the rear planetary ring gear.

The Bottom Line

Now that you know the TH350 transmission identification, decoding, and super-tuning, you have a better knowledge of your transmission. In the same vein, you’re well informed on how to improve it to be more durable and handle street racing. And given that this is a transmission that has stood the test of time, its rebuild will yield even more impressive results.

How to Update Your Vehicle’s Transmission Systems to Factory Specifications


An efficient transmission system is essential for the smooth functioning of any vehicle. When you start experiencing unusual sounds, odd odors, delayed movements, or fluid leaks in your car, it is the right time to go for quick repair service. In such scenarios, users can either replace their transmission systems or rebuild it with the help of specialized kits.

Rebuilding a transmission system is always a better option than replacing it entirely. There is no point in getting the entire system changed when you can get the damaged parts fixed at a much lower price. Once the system has been taken apart, any damaged component present inside can be quickly replaced. For a durable rebuilding, the following components are essential:

Soft Parts

This comprises all the transmission parts that wear out easily and degrade the overall efficiency of the system. A master rebuilding kit consists of spare clutches, bands, seals, gaskets, bushings, bearings, and sealing rings for replacing the damaged ones.

Hard Parts

This includes additional hardware components including solenoids and transmission cases that are essential for completely upgrading a transmission system. It is better to opt for automatic transmission rebuild kits that come with these components to avoid added expenses.

Transmission Fluid

High-quality transmission fluids are essential for thorough cleaning of the system. These fluids are vehicle-specific and should be used only if they comply with the technical specifications of the manufacturer.

Gearstar Performance Transmissions is a dedicated supplier of high-performance automatic transmissions built by skilled technicians. If you want to buy automatic transmission rebuild kits, Gearstar Performance Transmissions is a good way to go.

What Is a Lockup Torque Converter?

What Is a Lockup Torque Converter? - Gearstar Performance Transmissions

Have you ever wondered what a lockup torque converter, or when should a torque converter lockup? If you have, then let’s explain each of these to you, and generally, all you need to know about a torque converter. But first off, you already get the picture that this is a major component in your car. And that being so, its function aid the car’s performance.

Understanding Torque Converters

A torque converter is a coupling that sends rotating power to a rotating driven load. This power moves from the prime mover such as an internal combustion engine before it gets to the load. It can, therefore, be said that the torque converter creates a connection between the power source and the load in an automatic transmission.

This component is also connected to the flexplate directly, and the latter connects directly to the crankshaft. A torque converter has the major characteristic of multiplying torque if the output rotational speed is low. And this multiplication enables the fluid from the turbine’s curved vanes to deflect off the stator.

The early designs of the torque converter caused an RPM slippage of fluid between its turbine and impeller. When that happens, there is often a disturbance in the oil and this turbulence leads to the generation of heat. Automakers began to use air vanes positioned outside the torque converter in a bid to reduce the heat and cool the oil.

Nonetheless, this structure was used in small vehicles and it showed very little success. The oil was moved through the transmission cooler just to reduce the heat, but at the expense of energy and fuel being wasted.

What Is a Lockup Torque Converter?

Lockup torque converters are a type of converter that has a clutch. The engagement of this clutch causes the engine to lock to the transmission input shaft thereby leading to a direct 1:1 drive ratio. A lockup torque converter is used since it offers fuel economy, enabling you to use fuel minimally while on that joy ride.

History of Lockup Converters

Lockup torque converters gained popularity when it was discovered that manual transmissions are more fuel-efficient than automatic transmissions. The old torque converters also led to a loss in RPM between the gearbox’s crankshaft and input shaft. For this reason, it earned automatics the name slushbox at the time.

On the other hand, car manufacturers had to meet fuel economy targets set by the government. Accordingly, automatic transmissions were made to have an overdrive which helps to improve fuel economy. And this overdrive enabled the engine to turn while in lower RPM as the vehicle accelerates at a fast speed.

While this was an advantage, it wasn’t all so rosy when the engine turned slowly given that there was a slippage of the torque converter. As the torque converter slipped, it generated heat, which could potentially affect the converter and transmission negatively.

This heat also impacted on fuel economy, thereby overriding the purpose the overdrive was used in the first place. Accordingly, a lock-up of the converter helped to curb this slippage, and at the same time reduce heat and improve fuel economy.

Stages of Operation

The operation of the lockup converter is a bit complicated but one can still gain an understanding of it. In this case, there is a lock of the turbine to the torque converter’s case by the hydraulic pressure and this occurs when the crankshaft and input shaft are to turn at the same time while driving.

The engagement of the lockup clutch causes the fluid in the converter to rotate and at a speed similar to other components of the converter. The good thing is, heat is curbed significantly and so is the oil turbulence. The movement of the fluid can be attributed to the circulation which cycles the fluid through the cooler.

Furthermore, the lock-up mechanism takes advantage of a frictional clutch which is managed by a hydraulic pressure circuit. The engagement of the mechanism causes the components of the torque converter to serve as a rotating flywheel mass. As a result, this helps to reduce the load on the radiator while promoting fuel economy.

Lockup Torque Converter Failures

A torque converter lockup clutch may fail and there are different ways this failure can occur. For instance, this component can remain locked up, and as such, it causes the engine to stall as the car is braked. Another way it can fail is if the component does not lock and that results in increased fuel consumption as well as radiator temperature.

Finally, the converter can tend to slip when it is engaged, thereby allowing the engine speed to increase at a constant speed. It is worth noting that a torque converter may not lockup for the following reasons:

    • A cold engine temperature: There are cases where the converter may not lockup except the coolant temperature reaches 120°F.
    • Lockout of the overdrive unit: An overdrive unit that is locked-up causes the torque converter lockup to also be locked out.

Signs of a Failing Torque Converter

There are times when your lockup clutch will not engage, and you can easily spot out when that happens. To this, you need to pay attention to the transmission shift timing and quality. You can also use an auxiliary tachometer since there are cases where the lockup clutch engagement may be gentle with a minor change of engine speed.

On the other hand, torque converters will tend to unlock from the application of the brake or at the release of the throttle. The disengagement of the clutch may be easier to spot out compared to the engagement, given that it occurs gradually in some cars.

The Bottom Line

A lockup torque converter is important in automatic transmissions to reduce slippage. And once slippage is curbed, heat generation is minimal while fuel economy is improved. This and many more have been outlined above to give you an insight into this component and why you may need one.