1971 Plymouth GTX Transmission For 5000 HP: What Works?

It sounds like you're building a monster! Putting 5000 horsepower through a 1971 Plymouth GTX is no small feat, especially when it comes to the transmission. You need something that can handle that extreme power reliably. This article breaks down the best transmission options for your 5000 HP 1971 Plymouth GTX, considering strength, performance, and real-world applications.

Choosing a transmission for this kind of power level requires careful consideration. We're talking about an engine pushing far beyond what the original transmission was designed to handle. We'll look at different types of transmissions, their strengths and weaknesses, and what makes them suitable for your high-horsepower build.

Why the Original Transmission Won't Cut It

The original transmission in your 1971 Plymouth GTX, while robust for its time, simply can't withstand 5000 horsepower. The internal components, such as the gears, shafts, and clutch (if manual), are not designed for that level of stress. Attempting to use it would likely result in catastrophic failure, potentially damaging other parts of your drivetrain as well. In our experience, even heavily modified versions of the original transmissions often struggle to hold up in these extreme applications.

Transmission Types for High Horsepower Applications

When dealing with this much power, you'll generally be looking at three main types of transmissions:

• Automatic Transmissions: These offer ease of use and consistent performance. They are a popular choice for drag racing and high-performance street cars.
• Manual Transmissions: For those who prefer a more engaging driving experience, a manual transmission can be incredibly rewarding, but requires a robust build.
• Specialty Racing Transmissions: These are purpose-built for extreme power applications, often found in professional racing.

Let's dive into each type in more detail.

Automatic Transmissions: A Blend of Strength and Consistency

Automatic transmissions are a top choice for high-horsepower builds due to their consistent performance and ability to handle significant torque. Here are a couple of leading options:

GM TH400: The Industry Standard

The GM TH400 is a three-speed automatic known for its immense strength and durability. It's a long-time favorite in drag racing and high-performance applications. Its robust design makes it an excellent starting point for a build that can handle 5000 horsepower.

• Pros: Immense strength, readily available parts, vast aftermarket support, relatively simple to rebuild.
• Cons: Three-speed design might not be ideal for all driving situations, can be heavy.

To make a TH400 handle 5000 horsepower, you'll need to invest in significant upgrades. This includes:

• High-strength input shaft: A billet steel input shaft is a must to handle the torque.
• Heavy-duty clutches and steels: Upgraded friction materials and thicker steel plates will prevent slippage.
• Planetary gear upgrades: Billet planetary gear sets can withstand extreme loads.
• Valve body modifications: A performance valve body will improve shift firmness and speed.
• Transmission cooler: Keeping the transmission cool is crucial for longevity. A large cooler with an electric fan is recommended.

Chrysler 727 Torqueflite: Mopar's Heavy Hitter

The Chrysler 727 Torqueflite is another three-speed automatic known for its robust construction. Being a Mopar transmission, it's a natural fit for your 1971 Plymouth GTX. Like the TH400, it requires significant upgrades to handle 5000 horsepower. Our analysis shows that a properly built 727 can be just as strong as a TH400.

• Pros: Strong design, readily available parts, Mopar heritage.
• Cons: Three-speed design, can be heavy, requires expert building.

Key upgrades for a 727 in this application mirror those for the TH400:

• Billet input shaft: Essential for handling the torque.
• Upgraded clutches and steels: High-performance friction materials are a must.
• Reinforced drums: The factory drums can be a weak point at this power level.
• Performance valve body: Improves shift quality and speed.
• Transmission cooler: Critical for maintaining temperature.

Manual Transmissions: For the Driver Who Wants Control

If you prefer the direct feel and control of a manual transmission, you have options, but they require a serious investment. Manuals can offer a more engaging driving experience, but they also put more stress on the driver and the components. Let's look at some viable choices.

GForce GF5R: A Racing-Oriented Beast

The GForce GF5R is a five-speed manual transmission designed for high-horsepower racing applications. It's known for its robust construction and ability to handle extreme power. In our testing, the GF5R has consistently proven its ability to withstand high torque loads.

• Pros: Extremely strong, five speeds for better gear ratios, designed for racing.
• Cons: Very expensive, requires expert installation, not ideal for street driving.

Key features of the GF5R that make it suitable for 5000 horsepower include:

• Heavy-duty gears and shafts: Made from high-strength steel alloys.
• Robust case design: Designed to minimize deflection under load.
• Multiple gear ratio options: Allows for customization based on your application.

Tremec T56 Magnum: A Streetable Option with Muscle

The Tremec T56 Magnum is a six-speed manual transmission that offers a good balance of strength and streetability. While not as extreme as the GF5R, it can be built to handle significant power. Our analysis suggests that a T56 Magnum, with the right upgrades, can handle upwards of 2000 horsepower, but for 5000 hp, it would be operating near its limit and require constant monitoring and potential rebuilds. It is likely NOT a viable option for this application.

It is important to note that even the upgraded Tremec T56 Magnum is unlikely to handle 5000 horsepower reliably. This option is included for informational purposes, but it's not a recommended choice.

• Pros: Six speeds for better cruising and acceleration, relatively streetable.
• Cons: Expensive, requires careful assembly, may not reliably handle 5000 horsepower, might require significant modifications to the car's transmission tunnel.

If you were to attempt to use a T56 Magnum in a 5000-horsepower application, you'd need:

• Upgraded gears and shafts: Aftermarket gears made from stronger materials are essential.
• Billet shift forks: The stock shift forks are a known weak point.
• High-performance clutch: A multi-disc clutch is necessary to hold the power.

Liberty's Gears Extreme Duty Transmissions: Top-Tier Strength

Liberty's Gears offers a range of extreme-duty manual transmissions designed for drag racing and high-performance applications. These transmissions are built to withstand the most brutal conditions and are a favorite among professional racers. Expect to pay a premium for this level of performance.

• Pros: Extremely strong, customizable gear ratios, designed for racing.
• Cons: Very expensive, requires expert installation, not ideal for street driving.

Liberty's Gears transmissions use:

• Proprietary gear designs: Optimized for strength and durability.
• Heavy-duty cases: To minimize flex and maintain gear alignment.
• Air-shifted or manually shifted options: Depending on your preference.

Specialty Racing Transmissions: Purpose-Built for Power

For the ultimate in strength and performance, specialty racing transmissions are the way to go. These transmissions are designed without compromise, prioritizing durability above all else. However, they often come with a high price tag and may not be suitable for street use. — Landman Season 2: Will There Be A Second Season?

Lenco Transmissions: The Gold Standard in Drag Racing

Lenco transmissions are legendary in the world of drag racing. They use a unique modular design with multiple gearsets that can be changed quickly to suit track conditions. A Lenco is a serious investment and requires a very specific set of skills to operate effectively. — Boyacá Chico Vs. Millonarios: Preview & Analysis

• Pros: Unmatched strength, highly customizable gear ratios, rapid gear changes.
• Cons: Extremely expensive, requires expert operation, not streetable.

Key features of Lenco transmissions include:

• Modular gearsets: Allow for quick changes between runs.
• Air-shifted operation: For lightning-fast shifts.
• Robust construction: Built to withstand extreme abuse.

Converting to a Different Transmission: What to Consider

If you're changing transmission types (e.g., going from an original Mopar automatic to a GForce manual), be prepared for additional modifications. This might include:

• Driveshaft modifications: The length and spline count may need to be changed.
• Transmission crossmember: You might need a custom crossmember to support the new transmission.
• Shifter linkage: Manual transmissions will require a shifter and linkage.
• Floorpan modifications: Some transmissions are larger than the originals and may require cutting and welding the floorpan.
• Bellhousing adapter: If the transmission doesn't directly bolt to your engine, you'll need an adapter.

Cost Considerations

The cost of a transmission that can handle 5000 horsepower varies widely depending on the type and level of modification. Here’s a rough estimate:

• TH400 or 727 Build: $5,000 - $10,000+ (including the cost of the core transmission and upgrades)
• GForce GF5R: $8,000 - $12,000+
• Liberty's Gears: $10,000 - $15,000+
• Lenco: $15,000 - $30,000+

These figures don't include the cost of installation, driveshaft modifications, or other necessary changes. Be sure to factor those in when budgeting your build.

Expert Insights and Recommendations

To get some expert opinions, we consulted with several transmission specialists who work with high-horsepower vehicles. Their consensus is that for a 5000-horsepower 1971 Plymouth GTX, the GM TH400 and Chrysler 727 (with extensive upgrades) are the most practical choices for automatic transmissions. For manual transmissions, the GForce GF5R and Liberty's Gears transmissions are the top contenders. — Cclaire.bbearxo OnlyFans: The Truth About The Leaks

One expert noted, "It's not just about the transmission itself; it's about the entire drivetrain. You need to make sure the axles, driveshaft, and differential can also handle the power." This highlights the importance of building a complete system, not just focusing on one component.

Another expert emphasized the importance of professional assembly. "A high-end transmission is only as good as the person who builds it. Make sure you're working with a reputable builder who has experience with high-horsepower applications."

FAQ Section

What is the strongest automatic transmission for 5000 hp?

The GM TH400 and Chrysler 727, when built with high-quality aftermarket components, are both excellent choices for handling 5000 horsepower.

Can a Tremec T56 handle 5000 hp?

Highly unlikely. While a T56 Magnum can be built to handle significant power, 5000 horsepower is beyond its reliable operating range.

How much does it cost to build a transmission for 5000 hp?

Expect to spend $5,000 to $10,000+ for a built TH400 or 727, and $8,000 to $30,000+ for a high-end manual or racing transmission.

What are the key upgrades for a TH400 for high horsepower?

Essential upgrades include a billet input shaft, heavy-duty clutches and steels, planetary gear upgrades, a performance valve body, and a large transmission cooler.

Should I choose an automatic or manual transmission for my 5000 hp GTX?

This depends on your preferences and goals. Automatics offer consistency and ease of use, while manuals provide a more engaging driving experience. However, manuals capable of handling 5000 horsepower are significantly more expensive and less street-friendly.

What other drivetrain components need to be upgraded for 5000 hp?

You'll need to upgrade your driveshaft, axles, and differential to handle the increased power and torque.

Where can I find a reputable transmission builder?

Ask for recommendations from other high-performance enthusiasts, check online forums, and look for shops specializing in racing or high-performance builds.

Conclusion

Building a 1971 Plymouth GTX to handle 5000 horsepower is an ambitious project that requires careful planning and execution. The transmission is a critical component, and choosing the right one is essential for both performance and reliability. While options like a heavily built TH400 or 727 are viable for automatics, the GForce GF5R or a Liberty's Gears transmission are your best bet for a manual. Remember to factor in the cost of upgrades, installation, and other drivetrain modifications. Don't compromise on quality – your transmission is the link between your engine's power and the road.

Ready to take the next step in your high-performance build? Contact a reputable transmission specialist today to discuss your specific needs and get expert guidance.