GM 8640307 Sun Gear Automatic Transmission TH350 TH250 69-86

( Brand: Gm ), ( Part Type: Sun Gear Transmission ), ( Oe/oem Part Number: 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 85, 84, 1969, 1970, 1971, 1972, 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982 ), ( Manufacturer Part Number: 8640307 ), ( Transmission Type: Automatic )

Review GM Th350 Sun Gear Shell Automatic Transmission 69-86 fits 350-C 250-C

The GM 8640307 TH350/TH250 Sun Gear is an essential component of automatic transmissions used in various General Motors vehicles from 1969 to 1986. This sun gear is specifically designed for 350-C and 250-C engines.

This sun gear, a critical part of the transmission's planetary gear system, is responsible for transferring engine power to the transmission's planetary gears. The TH350 and TH250 are three-speed automatics with overdrive, making them popular choices for classic cars and trucks.

The GM 8640307 sun gear is precision-engineered to ensure smooth and efficient power transmission from the engine to the transmission. It is made of high-strength materials to withstand the rigors of continuous use, ensuring longevity and durability. The sun gear features a robust design, with a large diameter and multiple splines to securely connect it to the engine crankshaft and transmission input shaft.

When it comes to fitment, this sun gear is specifically designed for use in GM vehicles from the 1969 to 1986 model years with 350-C and 250-C engines. It is compatible with various transmission models, including TH350 and TH250. Installation is straightforward, requiring only standard hand tools and following the recommended installation procedures.

It is important to note that the GM 8640307 TH350/TH250 Sun Gear is a wear item and will eventually need to be replaced. Signs of a worn sun gear include difficulty shifting gears, grinding noises from the transmission, or the vehicle not responding properly when shifting. Regular maintenance, such as transmission fluid changes and inspections, can help extend the life of the sun gear and other transmission components.

In summary, the GM 8640307 TH350/TH250 Sun Gear is a crucial component of automatic transmissions used in various GM vehicles from 1969 to 1986. It is designed for use with 350-C and 250-C engines and is responsible for transferring engine power to the transmission's planetary gears. This sun gear is precision-engineered for durability, efficiency, and smooth power transmission. Regular maintenance is essential to ensure the longevity of this and other transmission components.

The GM 8640307 TH350/TH250 sun gear automatic transmission is a popular choice for various classic and muscle cars produced between 1969 and 1986 with 350-c and 250-c engines. Here's a brief analysis of the advantages and disadvantages of purchasing this transmission.

1. Durability: Known for its robustness and longevity, this transmission is a favorite among enthusiasts for its ability to handle high horsepower and torque outputs.

2. Compatibility: Widely used in various classic cars, the TH350/TH250 sun gear transmission provides a vast aftermarket support system, making it easier to find parts and professionals for repair or rebuild.

3. Smooth operation: The TH350 transmission is renowned for its smooth and reliable performance, making for an enjoyable driving experience.

4. Versatility: The TH350/TH250 sun gear transmission can be used in a variety of applications, including street use, drag racing, and off-road conditions, making it a versatile option for car owners.

1. Complexity: The TH350/TH250 sun gear transmission is a complex piece of machinery with numerous components, which can make diagnosing and repairing issues more challenging for the average mechanic.

2. Weight: With its heavy-duty design, this transmission can add significant weight to the vehicle, negatively impacting fuel economy and overall performance.

3. Cost: Due to its popularity and extensive use, the TH350/TH250 sun gear transmission can be expensive to purchase, especially when compared to newer, more modern automatic transmissions.

4. Maintenance: Regular maintenance, such as transmission fluid changes and filter replacements, is crucial to keep this transmission running smoothly and reliably.

The GM 8640307 TH350/TH250 sun gear automatic transmission is a powerful, durable, and versatile option for car enthusiasts looking to enhance their classic or muscle car's performance. Its smooth operation, widespread compatibility, and robust design make it a favorite among enthusiasts. However, its complexity, weight, and maintenance requirements are important factors to consider before making a purchase. Ultimately, the decision to buy this transmission depends on your specific needs, budget, and technical capabilities. If you're willing to invest in the upkeep and have the resources to handle any potential complications, the TH350/TH250 sun gear transmission could be an excellent addition to your vehicle.

Details:

Used original direct clutch drum for GM th350, th350c, TH250 and 250c. This is the heavy duty sun shell with thicker .168 wall.

part #: 8640307 prices

• $24.99-$39.99

specifications addedclutch:

• for models: 350-c, 250-c
• brand: Gm
• part type: Sun Gear Transmission
• oe/oem part number: 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 85, 84, 1969, 1970, 1971, 1972, 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982
• manufacturer part number: 8640307
• transmission type: Automatic

seller addedclutch:

• # reviews: 1590
• rating: 99.6%
• city: Hays, Kansas

offer addedclutch:

• quantity: 1
• options: Ship-to-home
• started: April 23, 2026
• sold: 0
• availability: In Stock

payments addedclutch:

• wallet: Google-pay
• credit card: Diners-club
• other

shipping addedclutch:

• service: USPS Ground Advantage
• type: Calculated
• class: Standard
• transit: 5-11 Days
• carrier: USPS
• cost: $18.00

returns addedclutch:

• policy: No Returns

general addedclutch:

• Transmission Drivetrain > Clutch Parts Kits > Additional Clutch Parts
• condition: Used

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