SPEEDWAY MOTORS 91029100 Automatic Transmission TH350

( Brand: Speedway Motors ), ( Manufacturer Part Number: 91029100 ), ( Country Of Origin: United States ), ( Type: Automatic Transmissions ), ( California Prop 65 Warning: True )

Review SPEEDWAY MOTORS Automatic Transmission Chevy Th350 New

The **Speedway 91029100 Automatic Transmission** is a high-performance, direct-fit replacement for the stock **Chevrolet TH350 3-speed automatic transmission**, meticulously engineered to restore power, reliability, and durability to classic muscle cars, trucks, and performance applications. Built with precision-crafted components, this transmission delivers seamless shifting, enhanced torque capacity, and improved longevity compared to the original factory unit, making it an ideal choice for enthusiasts seeking a balance of strength and smooth operation. The 91029100 features a robust **cast aluminum housing** reinforced with high-strength steel components, ensuring resistance to warping and stress under heavy loads, whether hauling, towing, or pushing through aggressive driving conditions. Inside, a **heavy-duty planetary gearset** with upgraded bearings and seals minimizes wear while maximizing efficiency, allowing for effortless engagement of forward and reverse gears without the sluggishness often associated with aging transmissions. The **direct-fit design** eliminates the need for extensive modifications, as it seamlessly replaces the stock TH350 with minimal adjustments, preserving the original bellhousing and linkage setup for compatibility with stock or aftermarket accessories.

One of the standout features of the Speedway 91029100 is its **upgraded valve body**, which enhances shift quality and responsiveness, reducing hunting and providing quicker, more precise gear changes. The transmission also incorporates a **strengthened torque converter**, often paired with a **heavy-duty pump**, to improve fluid circulation and cooling, preventing overheating during prolonged use or under high-stress conditions. Whether installed in a **Chevrolet Chevelle, Camaro, or full-size truck**, or in a **GMC or Pontiac** application, this transmission is engineered to handle the demands of modern driving while maintaining the classic feel of a well-tuned automatic. Built to withstand the rigors of high-performance driving, the Speedway 91029100 is backed by rigorous testing to ensure reliability, making it a trusted upgrade for both restoration projects and high-mileage vehicles. With its combination of durability, ease of installation, and performance-enhancing features, this transmission is the perfect solution for drivers who demand both power and precision from their classic or modified vehicles.

### **Pros and Cons of Buying a 1991 Chevrolet Th350 with a Speedway 91029100 Automatic Transmission**

#### **Pros**

1. **Reliable Engine and Transmission**

The **Chevy 350 V8** (Th350) is a well-known, durable engine that has been used in trucks, SUVs, and performance applications for decades. When properly maintained, it can last well over 200,000 miles. The **Speedway 91029100** is a **4-speed automatic transmission** (likely a **THM400 or THM700R4 variant**) that, when in good condition, provides smooth shifting and decent torque conversion.

2. **Strong Towing and Hauling Capability**

The **350 V8** produces **around 200 250 horsepower** (depending on modifications) and **300 350 lb-ft of torque**, making it suitable for light to moderate towing (up to **5,000 7,000 lbs** with proper setup). This is ideal for trucks, SUVs, or even classic car builds.

3. **Aftermarket Support and Availability**

The **350 V8** has an extensive aftermarket, meaning you can find **performance parts, upgrades, and rebuild kits** easily. The **Speedway transmission** (if it s a **THM400 or similar**) also benefits from aftermarket support, including **rebuilds, torque converters, and shift kits**.

4. **Fuel Efficiency (Compared to Modern V8s)**

While not as efficient as modern engines, the **350 V8** still gets **better mileage than a modern muscle car V8** (around **12 18 MPG** in a truck, depending on drivetrain and load). This is better than a **modern 5.3L V8** in some cases.

5. **Classic Truck/SUV Applications**

If you're restoring a **full-size Chevy truck (C/K), GMC Sierra, or even a Suburban/Yukon**, this engine and transmission combo is a **common, reliable choice**. Many classic trucks use this setup, making parts easier to source.

6. **Potential for Modifications**

The **350 V8** can be **easily tuned** (with **Holley, Edelbrock, or LS-based swaps**) for more power. The **Speedway transmission** can also be upgraded with a **heavy-duty torque converter** or **performance fluid** for better shifting.

7. **Lower Cost of Ownership (If Well-Maintained)**

If the engine and transmission have been **properly serviced**, they can be **cheaper to maintain** than a modern turbocharged V8. Basic maintenance (oil changes, valve adjustments, transmission fluid) is straightforward.

---

#### **Cons**

1. **Potential Transmission Issues**

The **Speedway 91029100** (likely a **THM400 or THM700R4**) can develop **slippage, rough shifting, or internal wear** if not maintained. **Automatic transmissions from this era** often require **frequent fluid changes** (every **30,000 50,000 miles**) to prevent failure. If neglected, **rebuilding or replacing it** can be **expensive ( $1,500 $3,000 )**.

2. **Throttle Body and Emissions Concerns**

Many **1990s Chevy trucks** have **throttle body issues** (carbon buildup, sticking) and **emissions-related problems** (EGR, PCV, O2 sensors). If the truck isn t **modified for emissions compliance**, it may **fail smog checks** or require **expensive fixes**.

3. **Fuel Economy Limitations**

A **350 V8 automatic** will **never be as fuel-efficient** as a modern **4-cylinder or diesel**. Expect **around 12 18 MPG** in a truck, which is **worse than a modern V6 or turbocharged 4-cylinder**.

4. **Rust and Structural Wear (If from a Truck/SUV)**

Many **1990s Chevy trucks** suffer from **frame rust, suspension wear, and electrical gremlins**. If buying a **used truck**, inspect for **frame rot, rusted axles, and worn-out bushings**.

5. **Modern Compatibility Challenges**

If you plan to **swap this engine into a newer vehicle**, you may face **electrical, wiring, or drivetrain mismatches**. Modern trucks often use **different cooling systems, fuel injection, and drivetrain components** that may not be compatible without **major modifications**.

6. **Noise and Vibration**

A **high-mileage 350 V8** can develop **rod knock, valve train noise, or excessive vibration**, especially if **not properly balanced or tuned**. The **transmission can also whine or slip** if fluid is old or clutches are worn.

7. **Resale Value is Low**

Unlike a **modern turbocharged V8 or diesel**, a **1991 350 V8 with an automatic** will **depreciate quickly** and have **limited resale value** unless it s in **showroom condition**.

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### **Conclusion**

- You need a **reliable, high-torque V8** for **towing, hauling, or classic truck restoration**.

- You **plan to maintain it properly** (regular **oil changes, transmission fluid flushes, and inspections**).

- You re **okay with lower fuel efficiency** and **potential emissions issues**.

- You **enjoy working on classic engines** and don t mind **some wear-and-tear** over time.

- You want **modern fuel efficiency or emissions compliance** without modifications.

- You **can t afford transmission or engine repairs** if they fail.

- You re looking for a **low-maintenance, high-resale-value** vehicle.

- You need **seamless integration** with a **modern vehicle** without major modifications.

---

### **Recommendation**

If you **find a well-documented, low-mileage example** (under **100,000 miles**) with **proper maintenance records**, this setup can be an **excellent investment** for **towing, classic builds, or off-road use**. **Prioritize:**

**Transmission fluid history** (must be changed regularly).

**Engine compression check** (no major wear).

**No rod knock or excessive vibration**.

**Rust-free frame and drivetrain** (if buying a truck).

If the **transmission has unknown service history** or the **engine shows signs of wear**, **budget for a rebuild** (or consider a **used rebuilt transmission**).

- A **used 350 V8 with a known-good THM400/700R4** (if you can verify fluid changes).

- A **modern turbocharged V8 (L96, LS3, or LT4)** if you need **better fuel economy and reliability**.

- A **diesel (Duramax, Powerstroke, Cummins)** if **towing is the primary use**.

If you re **restoring a classic truck or building a performance project**, the **1991 350 V8 with a Speedway automatic** is a **solid, proven choice** just **expect maintenance and don t expect modern efficiency**.

Details:

part #: 91029100 price

• $1784.99

specifications autotransmissionsgo:

• for makes: Chevy
• brand: Speedway Motors
• mpn: 91029100
• country of origin: United States
• type: Automatic Transmissions
• california prop 65 warning: True

payments autotransmissionsgo:

• other
• credit card: Mastercard
• wallet: Paypal

returns autotransmissionsgo:

• paid by: Seller
• time: 30 Days
• policy: Returns Accepted

seller autotransmissionsgo:

• # reviews: 18928
• city: Gilbert, Iowa
• rating: 99.7%

offer autotransmissionsgo:

• quantity: 1
• started: March 9, 2026
• best offers: True
• sold: 0
• availability: In Stock
• options: Ship-to-home

shipping autotransmissionsgo:

• cost: $300.00
• service: FedEx Ground / FedEx Home Delivery
• transit: 2-4 Days
• class: Standard
• type: Fixed
• carrier: FedEx

general autotransmissionsgo:

• condition: New other see details
• Car Truck Parts Accessories > Transmission Drivetrain > Automatic Transmission

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