1. Automatic Transmissions Products
  2. sku: 23704641210972731
  3. SPEEDWAY 91029106

SPEEDWAY MOTORS 91029106 Transmission Horsepower TH350

fits model: 4wd, 450.

91029106 Speedway Motors Remanufactured 4wd Th350 Transmission Rated 450 Horsepower

( Brand: Speedway Motors ), ( Manufacturer Part Number: 91029106 ), ( Type: Automatic Transmissions ), ( California Prop 65 Warning: True )

Review SPEEDWAY MOTORS Remanufactured Th350 Transmission Rated Horsepower fits 4WD 450

The **Speedway 91029106 4WD TH350 Transmission** is a high-performance, heavy-duty automatic transmission designed to deliver unmatched durability and power handling for Ford s legendary **TH350-based 4WD applications**, particularly those pushing **450 horsepower** or more. Built to withstand the relentless demands of towing, hauling, and off-road adventures, this transmission is engineered with precision-crafted internal components that ensure smooth, reliable operation even under extreme loads. The **91029106** model is a direct replacement for the stock TH350, featuring upgraded valve bodies, reinforced planetary gears, and a hardened torque converter housing to prevent warping and premature wear critical for engines generating **450 horsepower** or higher. Its **4-speed automatic design** provides seamless shifting between gears, while the **heavy-duty clutch packs and band assemblies** ensure consistent engagement and reduced slippage, even under heavy torque loads. Whether paired with a **Ford 302, 351 Cleveland, or 428 Cobra Jet**, this transmission is built to handle the power without compromising longevity. The **precision-machined internal components** and **high-quality seals** minimize fluid leakage and internal friction, extending the transmission s lifespan while maintaining optimal performance. Ideal for **muscle cars, truck builds, and performance applications**, the Speedway 91029106 is a trusted upgrade for those seeking a **durable, high-performance transmission** that can keep up with aggressive driving styles and demanding workloads. With its **reputation for reliability and strength**, this transmission is a must-have for enthusiasts looking to maximize power delivery while ensuring long-term durability.

The **Speedway 91029106 4WD TH350 transmission** is a popular aftermarket torque converter and transmission upgrade for Ford trucks, particularly the F-150, F-250, and F-350 with the 7.3L Power Stroke engine. Below is a detailed breakdown of its pros and cons, followed by a conclusion and recommendation.

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### **Pros of the Speedway 91029106 4WD TH350 Transmission**

1. **Increased Horsepower and Torque Handling**

The TH350 transmission is designed to handle higher power levels than the stock 4R75E or 6R140 transmissions. This unit is rated for **450 horsepower and 500 lb-ft of torque**, making it suitable for heavily modified trucks, towing applications, or those running turbocharged or supercharged engines. It provides smoother shifting and better durability under heavy loads.

2. **Better Shift Quality and Performance**

The TH350 features a **stiffer valve body and stronger internal components** compared to the stock transmission. This results in quicker, more precise shifts and reduced slippage, especially in high-torque situations. The upgraded clutch packs and bearings also improve overall durability.

3. **Compatibility with Aftermarket Upgrades**

The TH350 is widely used in the aftermarket, meaning there are **plenty of supporting parts** available, such as upgraded clutches, torque converters, and fluid options. This makes it easier to fine-tune the transmission for optimal performance.

4. **Durability for Heavy-Duty Use**

Built with **heavier-duty internal components**, including stronger shafts, bearings, and synchronizers, the TH350 is designed to withstand the stresses of towing, hauling, or high-performance driving. It is less likely to fail prematurely under heavy loads compared to the stock transmission.

5. **Widely Available and Supported**

Speedway and other manufacturers (like Jegs, Summit Racing, and others) offer this transmission as a direct replacement or upgrade. There are also **tuning options** (such as adjusting the valve body or using a performance converter) to further optimize performance.

6. **Better for High-RPM Applications**

The TH350 s design allows it to handle **higher RPMs and power delivery** more effectively than the stock transmission, which can be a limiting factor in high-performance builds.

7. **Retains Stock Mounting Points**

The TH350 is designed to **bolt-in directly** to the stock transmission housing, making installation relatively straightforward for those with basic mechanical skills. No major modifications to the truck s frame or drivetrain are required.

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### **Cons of the Speedway 91029106 4WD TH350 Transmission**

1. **Higher Upfront Cost**

The TH350 transmission is **significantly more expensive** than the stock 4R75E or 6R140. Prices typically range from **$2,500 to $4,500 **, depending on whether you buy new or used, and whether additional components (like a torque converter or clutch) are included. This can be a major investment for enthusiasts on a budget.

2. **Requires Additional Modifications**

While the TH350 bolts in, **additional upgrades are often necessary** to fully realize its potential. These may include:

- **Upgraded torque converter** (a performance converter is recommended for high horsepower applications).

- **Performance transmission fluid** (such as Mopar ATF 4 or a synthetic alternative).

- **Upgraded clutch packs** (if running extreme power levels).

- **Tuning adjustments** (valve body modifications or ECU tuning for optimal shift points).

Without these, the transmission may not perform as intended.

3. **Potential for Overkill on Stock or Mildly Modified Trucks**

If your truck is **stock or only mildly modified** (e.g., 350-400 HP), the TH350 may be **more than necessary**. The stock 4R75E or 6R140 can handle these power levels adequately with proper maintenance. Installing a TH350 in this scenario is an **unnecessary expense** unless you plan to heavily modify the truck in the future.

4. **Learning Curve for Installation and Tuning**

Installing a TH350 requires **mechanical skill and patience**. While it bolts in, **alignment, fluid routing, and electrical connections** must be carefully handled. Additionally, **tuning the transmission** (e.g., adjusting shift points) may require a **transmission tuner or ECU programmer**, adding to the complexity and cost.

5. **Potential for Increased Wear Without Proper Maintenance**

Like any high-performance transmission, the TH350 **requires meticulous maintenance** to avoid premature wear. This includes:

- **Regular fluid changes** (synthetic fluid recommended).

- **Proper torque converter matching** (a slushy converter can cause excessive wear).

- **Avoiding extreme heat or overloading** (which can stress internal components).

Neglecting maintenance can lead to **early failure**, negating the durability benefits.

6. **Limited Stock Parts Availability**

Since the TH350 is an aftermarket unit, **stock parts (like gaskets, seals, or synchronizers) may be harder to find** compared to the original transmission. This means you ll often need to **source aftermarket replacements**, which can be more expensive.

7. **Potential for Voiding Warranty (If Applicable)**

If your truck is still under **factory warranty**, installing an aftermarket transmission like the TH350 may **void certain coverage**. Always check with the manufacturer before proceeding.

8. **Not All Engines Are Compatible**

While the TH350 works well with **7.3L Power Stroke, 6.0L Power Stroke, and 5.4L Triton engines**, it may require **additional modifications** for other Ford engines (e.g., 351W, 460, or 5.9L Power Stroke). Always verify compatibility before purchasing.

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### **Conclusion**

The **Speedway 91029106 4WD TH350 transmission** is a **strong upgrade** for Ford trucks running **450 horsepower**, especially those used for **towing, hauling, or high-performance applications**. It offers **superior durability, better shift quality, and the ability to handle extreme power levels** compared to the stock transmission. However, it comes with **higher costs, installation complexity, and the need for additional upgrades** to fully optimize performance.

For **stock or mildly modified trucks**, the TH350 may be **overkill and unnecessary**. In such cases, a **stock transmission with proper maintenance and fluid upgrades** could suffice. Conversely, for **serious powerhouses, towing rigs, or future-proofing a build**, the TH350 is a **wise investment** that will pay off in reliability and performance.

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### **Recommendation**

- **Buy the TH350 if:**

- Your truck is **running or will soon run 450 horsepower**.

- You plan to **tow heavy loads frequently** or use the truck for **high-performance driving**.

- You are **willing to invest in supporting upgrades** (torque converter, fluid, tuning).

- You have **basic mechanical skills** or access to a **transmission specialist** for installation.

- **Avoid the TH350 if:**

- Your truck is **stock or only mildly modified** (under 400 HP).

- You are **on a tight budget** and cannot afford additional upgrades.

- You **lack the time or mechanical ability** to properly install and maintain it.

- You **prioritize simplicity** and do not plan to push the truck to extreme limits.

**Final Verdict:** The Speedway 91029106 TH350 is a **premium transmission upgrade** that is **justified for high-power or heavy-duty applications**. For most enthusiasts, it is **not a "set it and forget it" solution** it requires **careful planning, installation, and maintenance** to perform optimally. If you are committed to maximizing your truck s performance and durability, it is a **solid choice**. Otherwise, a **stock transmission with proper maintenance** may be sufficient.

Details:

Features a Superior HD shift kit and new front pump gears for crisp, reliable shifting. Equipped with new USA-made frictions and seals for maximum durability performance. No kick down cable provision. Headquarters.

Includes all-new bushings and thrust washers to ensure smooth operation extended lifespan. Key Features. Note: Street King valve body modified with shift improvement feature for firmer, later shifts and manual downshifting. A 6-inch tail shaft is standard, with longer lengths available to suit your specific build requirements.

Note: Torque converter not included. Street King valve body modified with shift improvement feature for firmer, later shifts and manual downshifting. Specs Number of Gears Three Valve Body Standard Lockup Compatible No Material Type Aluminum Finish Natural Flex plate Included MFG. Part # 91029106 Condition New Brand Speedway Motors Sold Each Details Elevate your vehicles performance with our premium remanufactured 4WD TH350 Transmission, expertly engineered to deliver exceptional power and reliability for up 450 horsepower applications.

specifications autotransmissionsgo:

  • for models: 4wd, 450
  • brand: Speedway Motors
  • mpn: 91029106
  • type: Automatic Transmissions
  • california prop 65 warning: True

shipping autotransmissionsgo:

general autotransmissionsgo:

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

seller autotransmissionsgo:

  • city: Lincoln, Nebraska
  • rating: 99.8%
  • # reviews: 362864

returns autotransmissionsgo:

  • policy: Returns Accepted
  • time: 60 Days
  • paid by: Buyer

payments autotransmissionsgo:

  • other
  • credit card: Discover
  • wallet: Paypal

offer autotransmissionsgo:

  • availability: In Stock
  • sold: 0
  • quantity: 2
  • options: Ship-to-home
  • started: May 3, 2026
for models: 4wd, 450, type: automatic transmissions, california prop 65 warning: true,
category: auto parts > car truck parts accessories > transmission drivetrain > automatic transmission, sku: 23704641210972731,
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