Identifying the TH350 Transmission

The TH350 is a three-speed automatic transmission․ One key identifier is the modulator valve, located at the rear of the transmission case․ Also, look for a stamped VIN on a pad near the bellhousing․

Location of the Modulator Valve

The modulator valve’s location is a primary identifier for the TH350 transmission․ This valve is situated at the back of the transmission case․ This contrasts with other transmissions like the TH400, where the modulator is located on the side of the case․ The modulator valve plays a crucial role in regulating shift timing and quality based on engine vacuum․ Its presence and position at the rear make it a quick visual cue for identifying a TH350․ When attempting to identify a TH350, especially while it is still installed in a vehicle, locating the modulator valve at the rear of the transmission case is a simple and reliable method․ This method is often preferred because it’s easily accessible and doesn’t require a detailed inspection of casting numbers or other markings that might be obscured; The location of the modulator valve, combined with the shape of the transmission pan, provides a conclusive method for differentiating between the TH350 and other common GM transmissions such as the TH400 and Powerglide․ For a quick reference, remember: TH350 ⎯ Modulator at the rear; TH400 ー Modulator on the side․ This visual check simplifies the identification process, saving time and effort during diagnosis or replacement․

Transmission Pan Shape as an Identifier

The shape of the transmission pan is a reliable method for identifying a TH350 transmission․ The TH350 has a nearly square pan with one corner slightly angled or beveled․ This shape distinguishes it from other GM transmissions like the TH400, which has a more irregular pan shape․ Counting the number of bolts on the transmission pan can also aid in identification․ The TH350 pan typically has 13 bolts․ While some transmissions may share similar pan shapes, the combination of the near-square shape and the number of bolts provides a high degree of accuracy in identifying the TH350․ This method is particularly useful when the transmission is installed in the vehicle, as the pan is usually easily accessible for visual inspection․ For instance, the Powerglide transmission has a different pan shape altogether, making it easy to differentiate from the TH350․ The Turbo 400 transmission pan, on the other hand, has a more complex shape with several distinct angles and a different bolt pattern․ Keep in mind that while pan shape is a good indicator, it’s always best to verify with other identifiers like the modulator valve location or casting numbers․ However, the pan shape provides a quick and easy way to narrow down the possibilities and guide your identification process․ Remember to check for the nearly square shape and confirm the presence of 13 bolts for a confident TH350 identification․

VIN Stamp Location on TH350

The Vehicle Identification Number (VIN) stamp on a TH350 transmission provides crucial information for verifying its origin and compatibility․ Typically, the VIN stamp is located on a machined pad on the transmission case․ You can find this pad on either the driver’s side housing, near the shifter linkage, or on the right side of the housing, just above the pan rail․ The partial VIN stamped on the TH350 usually includes a division code, followed by the last digit of the model year, a letter indicating the assembly plant where the transmission was manufactured, and a six-digit sequence number representing the vehicle’s serial number․ For example, a VIN stamp might look something like this: “1X123456”, where “1” represents the Chevrolet division, “X” represents the model year, and “123456” is the vehicle’s serial number․ This partial VIN should match the corresponding digits of the vehicle’s VIN to confirm that the transmission is original to the car․ The presence and legibility of the VIN stamp can also help to authenticate the transmission and ensure that it has not been tampered with or replaced․ It’s important to note that the exact location and format of the VIN stamp may vary slightly depending on the year and model of the vehicle․ However, the general area near the shifter linkage or above the pan rail is the most common location․ When inspecting a TH350 for a VIN stamp, be sure to clean the area thoroughly to remove any dirt or grease that may obscure the numbers․ Use a bright light and a magnifying glass if necessary to ensure accurate identification․ Cross-referencing the VIN stamp with the vehicle’s documentation can provide valuable confirmation of the transmission’s history and compatibility․

TH350 Transmission Length and Weight

The TH350 transmission is known for its compact dimensions and relatively light weight, making it a popular choice for a variety of vehicle applications․ The overall length of a TH350 transmission is approximately 21-3/4 inches (about 55․2 centimeters)․ This measurement typically includes the main case and the tailhousing, but it may vary slightly depending on the specific tailhousing configuration․ This relatively short length contributes to its versatility, allowing it to fit in a wide range of vehicle chassis without requiring significant modifications․ As for weight, the TH350 transmission typically weighs around 120 pounds (approximately 54․4 kilograms)․ This weight includes the transmission case, internal components, and bellhousing․ The use of aluminum alloy in the construction of the transmission case helps to keep the weight down, contributing to improved fuel efficiency and overall vehicle performance․ The combination of a compact length and manageable weight makes the TH350 a desirable option for both original equipment manufacturers (OEMs) and aftermarket enthusiasts․ Its size and weight allow for easier installation and integration into various vehicle platforms, while its robust design ensures reliable performance․ When considering a TH350 transmission for a project, it is important to verify the exact length and weight specifications to ensure proper fitment and compatibility with the vehicle․ Consulting with a transmission specialist or referring to the manufacturer’s specifications can provide accurate measurements and weight information․ Keep in mind that the weight may vary slightly depending on the specific components installed, such as the torque converter and fluid level․

GM Transmission Identification Methods

GM transmissions can be identified using several methods․ These include checking casting numbers on the case, date casting codes, and assembly date code stamping․ VIN stampings can also provide crucial identification information․

Casting Numbers

Casting numbers are a primary method for identifying GM transmissions, including the TH350․ These numbers are typically found on the main case, extension housing, and sometimes even the side cover (particularly on manual transmissions)․ These numbers, usually a series of digits and sometimes letters, are embedded into the metal during the casting process at the manufacturing plant․ They serve as a unique identifier for that particular casting design, indicating the specific mold and process used․ To locate the casting number on a TH350, carefully inspect the exterior of the transmission case․ Use a wire brush or solvent to clean any dirt or grime that may obscure the numbers․ It’s often helpful to use a flashlight to illuminate the surface, making the numbers easier to read․ Once you have found the casting number, cross-reference it with reliable GM parts databases or transmission identification guides․ These resources will provide information about the specific transmission model, the years it was produced, and the vehicles it was commonly used in․ Keep in mind that casting numbers only identify the specific casting design, not necessarily the exact internal components or modifications that may have been made to the transmission over time․ However, they provide a crucial starting point for determining the origin and intended application of the transmission․ Additionally, remember that different components of the transmission, such as the case and extension housing, may have different casting numbers․ Therefore, it’s essential to record all the numbers you find and compare them to available resources to ensure accurate identification․ In some cases, subtle variations in the casting numbers may indicate different production runs or minor design changes․ Therefore, pay close attention to even the smallest details when comparing the numbers to reference materials․ By carefully examining and cross-referencing the casting numbers, you can gain valuable insights into the history and characteristics of your TH350 transmission․

Date Casting Codes

Date casting codes are another essential tool for identifying and understanding the history of your TH350 transmission․ Unlike casting numbers, which identify the mold design, date casting codes reveal when the transmission case (or other components) was actually cast․ These codes are typically located near the casting numbers and consist of a combination of letters and numbers․ The code usually indicates the month, day, and year the casting was made․ Understanding these codes can help determine if the transmission is original to a particular vehicle and provide insights into its age․ To decipher date casting codes, you’ll need a reliable reference chart specific to GM transmissions․ These charts are readily available online and in specialized automotive literature․ The chart will explain how to interpret the letters and numbers in the code to determine the exact date of manufacture․ For example, a letter might represent the month (A for January, B for February, etc․), followed by numbers indicating the day and year․ When examining the date casting codes, pay attention to the chronological order of the components․ Ideally, the casting dates of the case, extension housing, and other major parts should be relatively close together․ Significant discrepancies in the dates could suggest that parts have been swapped or replaced over time․ It’s also important to consider the vehicle’s assembly date when evaluating the date casting codes․ The transmission casting date should generally precede the vehicle’s build date․ However, there may be a slight overlap as parts were manufactured and then assembled into vehicles․ Furthermore, keep in mind that date casting codes can be faint or obscured by dirt, rust, or paint․ Carefully clean the area around the casting numbers and use a flashlight to improve visibility․ In some cases, you may need to use a magnifying glass to accurately read the codes․ By meticulously examining and decoding the date casting codes, you can gain valuable information about the origin and authenticity of your TH350 transmission․ This information can be particularly useful for restoration projects or when trying to determine the original specifications of a vehicle․

Assembly Date Code Stamping

In addition to casting numbers and date casting codes, the TH350 transmission features an assembly date code stamping, providing another layer of identification and historical information․ This stamping reveals the specific date the transmission was assembled at the factory․ The assembly date code is typically found on a machined pad on the transmission case, often near the bellhousing or on the side of the case․ Unlike the raised casting numbers, the assembly date code is stamped into the metal, creating an indented impression․ The assembly date code usually consists of a combination of letters and numbers, similar to the date casting codes․ However, the format and meaning of the characters may differ slightly․ The code typically includes information about the month, day, and year of assembly, as well as a plant code indicating the specific factory where the transmission was built․ To accurately decode the assembly date code, you’ll need a reliable reference chart specific to GM transmissions․ These charts are available in various online resources and specialized automotive publications․ The chart will explain the meaning of each character in the code and provide the corresponding date and plant information․ When examining the assembly date code, it’s important to clean the area thoroughly to ensure clear visibility․ Use a wire brush or solvent to remove any dirt, grease, or paint that may be obscuring the stamping․ A magnifying glass can also be helpful for reading the small, closely spaced characters․ The assembly date code should generally align with the vehicle’s build date, although there may be some variation due to production timelines and inventory management․ A transmission assembly date that is significantly later than the vehicle’s build date could indicate that the transmission was replaced at some point․ The assembly date code can be a valuable tool for verifying the authenticity of a TH350 transmission and ensuring that it is appropriate for a particular vehicle․ This information is particularly important for restoration projects and collectors seeking to maintain the original specifications of their vehicles․ Furthermore, the assembly date code can provide insights into the production history of the TH350 transmission and its evolution over time․ By carefully examining and decoding the assembly date code, you can gain a deeper understanding of the TH350 transmission and its place in automotive history․

Aftermarket TCC Control Unit

The Turbo Hydra-Matic 350 (TH350) transmission, while a durable and reliable three-speed automatic, did not originally come equipped with a torque converter clutch (TCC) lockup feature in its early iterations․ The TCC is a mechanism that, when engaged, creates a direct mechanical connection between the engine and the transmission, eliminating slippage in the torque converter and improving fuel efficiency, especially at cruising speeds․ To address this limitation and enhance the TH350’s performance, aftermarket TCC control units have been developed and are available for installation․ These control units allow for the addition of a TCC lockup function to TH350 transmissions that were not originally equipped with it․ An aftermarket TCC control unit typically consists of a control module, wiring harness, and vacuum or electrical switch․ The control module monitors various parameters such as vehicle speed, engine load, and throttle position to determine when to engage the TCC․ The wiring harness connects the control module to the transmission, vacuum switch (if applicable), and power source․ The vacuum or electrical switch signals the control module when the appropriate conditions for TCC lockup are met․ When the control module determines that TCC lockup is desirable, it sends a signal to a solenoid within the transmission, which then engages the TCC․ This creates a direct mechanical connection between the engine and transmission, reducing slippage and improving fuel economy․ The benefits of installing an aftermarket TCC control unit on a TH350 transmission include improved fuel efficiency, reduced heat generation in the torque converter, and enhanced cruising performance․ By eliminating slippage in the torque converter, the engine operates more efficiently, resulting in better gas mileage․ The reduction in heat generation helps to prolong the life of the transmission fluid and components․ The enhanced cruising performance provides a more solid and responsive feel at highway speeds․ When selecting an aftermarket TCC control unit for a TH350 transmission, it’s important to choose a reputable brand and ensure that the unit is compatible with the specific year and model of the transmission․ Professional installation is recommended to ensure proper operation and avoid any potential damage to the transmission․ With the addition of an aftermarket TCC control unit, the TH350 transmission can be transformed into a more efficient and versatile unit, providing improved fuel economy and enhanced driving performance․ This upgrade is particularly beneficial for vehicles that are frequently used for highway driving or long-distance trips․ Moreover, when paired with an aftermarket TCC control unit, these can be desirable transmissions, and up to 10 more efficient at cruising speeds․