How Hard Is It To Rebuild A TH350 Transmission

Are you curious about the level of difficulty involved in rebuilding a TH350 transmission? If so, you’ve come to the right place! In this article, we will explore the challenges and intricacies of rebuilding a TH350 transmission, highlighting key factors that can make the process either straightforward or more demanding. Whether you’re a DIY enthusiast or a professional mechanic, this article will provide you with valuable insights on the complexities of rebuilding a TH350 transmission. So, let’s dive in and discover what it takes to tackle this task with confidence and success!

TH350 Transmission Overview

Introduction to TH350 transmission

The TH350 transmission is a popular automatic transmission that was manufactured by General Motors from the 1960s to the 1980s. It was commonly used in many GM vehicles, including Chevrolet, Pontiac, and Oldsmobile models. The TH350 transmission is known for its durability and reliability, making it a great choice for both daily driving and performance applications.

Basic components of a TH350 transmission

The TH350 transmission consists of several key components that work together to provide smooth and efficient shifting. Some of the basic components include:

  1. Bellhousing: This is the outer casing that connects the transmission to the engine. It also houses the torque converter, which is responsible for transmitting power from the engine to the transmission.

  2. Planetary Gear Sets: The TH350 transmission utilizes multiple planetary gear sets to provide different gear ratios. These gear sets allow for smooth shifting and optimal performance in a variety of driving conditions.

  3. Clutch Packs: The clutch packs are responsible for engaging and disengaging the gears within the transmission. They consist of a series of friction discs and steel plates that are stacked together.

  4. Valve Body: The valve body is an essential component that controls the flow of transmission fluid and activates the different clutches and bands. It is located on top of the transmission and contains various valves and passages.

  5. Bands: The TH350 transmission has two bands – the intermediate band and the reverse band. These bands are responsible for holding certain gears in place during operation.


Gather necessary tools and equipment

Before beginning the rebuild process, it is essential to gather all the necessary tools and equipment. Some of the tools you will need include a torque wrench, socket set, screwdrivers, snap ring pliers, and a clutch spring compressor. It is also recommended to have a transmission jack or a sturdy floor jack to support the transmission during removal and installation.

Acquire a rebuild kit

To rebuild a TH350 transmission, you will need a comprehensive rebuild kit that includes all the necessary parts, such as gaskets, seals, friction discs, and steel plates. It is essential to choose a high-quality rebuild kit from a reputable manufacturer to ensure the longevity and reliability of the rebuilt transmission.

Remove the transmission from the vehicle

Once you have gathered all the necessary tools and acquired a rebuild kit, the next step is to remove the transmission from the vehicle. This process may vary depending on the specific vehicle, but generally involves disconnecting the driveshaft, disconnecting electrical connectors and linkage, and removing the transmission mounting bolts. It is important to refer to a vehicle-specific repair manual or seek professional guidance to ensure the proper removal of the transmission.

How Hard Is It To Rebuild A TH350 Transmission


Drain the fluid and remove the pan

Before beginning the disassembly process, it is crucial to drain the transmission fluid and remove the transmission pan. This allows for easier access to the internal components of the transmission. It is important to use a suitable container to collect and dispose of the old transmission fluid properly.

Remove the valve body and governor

Once the pan is removed, the next step is to remove the valve body and governor. The valve body is typically held in place by a series of bolts or screws and is connected to various passages and valves within the transmission. The governor, which controls the shifting points of the transmission, is usually located at the rear of the valve body.

Disassemble the clutch packs and drums

After the valve body and governor are removed, you can proceed to disassemble the clutch packs and drums. This involves removing the retaining clips, snap rings, and other fasteners to separate the clutch packs and drums from the transmission. It is important to keep track of the order and orientation of the components for reassembly.


Inspecting the components for wear and damage

Once the transmission is disassembled, it is crucial to thoroughly inspect each component for any signs of wear, damage, or excessive wear. This includes examining the clutch discs, steel plates, bands, gears, and other internal components. If any parts show significant wear or damage, they should be replaced with new components from the rebuild kit.

Checking for proper clearances

In addition to inspecting for wear and damage, it is important to check for proper clearances between the various components. This involves using feeler gauges and other measuring tools to ensure that the clearances fall within the manufacturer’s specified tolerances. Proper clearances are essential for smooth operation and longevity of the rebuilt transmission.

How Hard Is It To Rebuild A TH350 Transmission


Thoroughly clean all disassembled parts

Cleaning the disassembled parts is a crucial step in the rebuilding process as it helps remove any dirt, debris, or old transmission fluid that may have accumulated over time. It is important to thoroughly clean each component using appropriate cleaning solutions and tools, such as parts cleaner, brushes, and compressed air. This ensures that the rebuilt transmission operates at its optimal performance.

Use appropriate cleaning solutions and tools

When cleaning the transmission components, it is essential to use suitable cleaning solutions and tools. Avoid using harsh chemicals or abrasive cleaners that may damage the delicate surfaces. Instead, opt for specialized transmission cleaning solutions that are safe for the components and will effectively remove any buildup or contaminants.


Install new seals and gaskets

During the reassembly process, it is important to replace all the old seals and gaskets with new ones from the rebuild kit. This ensures proper sealing and prevents leaks once the transmission is back in operation. Carefully install the new seals and gaskets according to the manufacturer’s instructions, ensuring a clean and accurate fit.

Reassemble the clutch packs and drums

After the seals and gaskets are in place, you can start reassembling the clutch packs and drums. Refer to the vehicle-specific repair manual or the rebuild kit instructions for the correct order and orientation of the clutch discs and steel plates. Pay close attention to any specific torque specifications for the fasteners and follow the recommended procedures for proper assembly.

Reinstall the valve body and governor

Once the clutch packs and drums are reassembled, you can proceed to reinstall the valve body and governor. Ensure that all valves, passages, and electrical connectors are properly aligned and connected. Tighten all the bolts or screws to the recommended torque specifications, but be careful not to overtighten and damage the components.

How Hard Is It To Rebuild A TH350 Transmission


Adjusting the linkage and bands

After the reassembly process, it is important to make necessary adjustments to the linkage and bands for proper transmission operation. This involves adjusting the shift linkage and throttle valve linkage to ensure smooth shifting and accurate transmission response. Additionally, the bands may need to be adjusted to achieve the correct band tension and prevent slippage.

Setting the endplay and clearances

In addition to the linkage and band adjustments, it is crucial to set the endplay and clearances to the manufacturer’s specifications. Endplay refers to the amount of axial movement in the transmission output shaft, and clearances refer to the gap between certain components. Proper endplay and clearances are essential for optimal performance and longevity of the rebuilt transmission.


Perform hydraulic and functional tests

Once the adjustments are made, it is important to perform hydraulic and functional tests to ensure the proper operation of the rebuilt transmission. This includes testing the hydraulic pressure, line pressure, and overall shifting performance. Use a transmission pressure gauge and follow the recommended testing procedures to accurately evaluate the transmission’s functionality.

Check for leaks and proper operation

After the hydraulic and functional tests, it is crucial to carefully inspect the rebuilt transmission for any signs of leaks or abnormal operation. Check for any fluid leaks, unusual noises, or slipping gears. If any issues are detected, they should be addressed promptly to avoid further damage and ensure the overall reliability of the transmission.

How Hard Is It To Rebuild A TH350 Transmission

Fluid Replacement

Refill the transmission with fresh fluid

Once all the necessary tests and inspections are completed, it is time to refill the transmission with fresh transmission fluid. Use the manufacturer-recommended fluid type and carefully pour it into the transmission through the appropriate fill port. It is important to follow the proper fluid level guidelines to ensure the transmission is not overfilled or underfilled.

Ensure proper fluid level and quality

After refilling the transmission, it is crucial to check the fluid level and quality to ensure optimal performance. Use the transmission dipstick or follow the manufacturer’s instructions to accurately measure the fluid level. Additionally, monitor the fluid color and consistency to ensure it is clean and free from any contaminants. Regular fluid maintenance is essential for the longevity of the rebuilt transmission.


Prepare the vehicle for transmission installation

Before installing the rebuilt transmission, it is important to prepare the vehicle by cleaning any mating surfaces, inspecting the transmission mounts, and ensuring proper alignment. Also, make sure to reconnect any electrical connectors, linkage, and cooling lines that were disconnected during the removal process. Proper preparation helps facilitate a smooth and successful transmission installation.

Reinstall the transmission and torque converter

Once the vehicle is prepared, you can proceed to reinstall the rebuilt transmission and torque converter. Carefully align the transmission with the engine, ensuring that all the mounting bolts line up with the corresponding holes. Gently slide the transmission into place and secure it using the proper torque specifications. Also, ensure that the torque converter is properly aligned and fully seated in the transmission.

Properly torque all fasteners

During the installation process, it is crucial to properly torque all the fasteners to the manufacturer’s recommended specifications. Use a torque wrench and follow the proper tightening sequence to ensure that the fasteners are secure but not overtightened. Overtightening can cause damage to the components, while undertightening may lead to loose connections and leaks.

In conclusion, rebuilding a TH350 transmission requires proper preparation, the right tools and equipment, and following a systematic approach. While it may seem daunting at first, with patience, attention to detail, and the help of a quality rebuild kit, anyone can successfully rebuild a TH350 transmission. Remember to consult a vehicle-specific repair manual or seek professional guidance if needed. With a properly rebuilt TH350 transmission, you can enjoy reliable and smooth shifting for many miles to come.

How Hard Is It To Rebuild A TH350 Transmission

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