Description
TCI Auto Automatic Transmissions 371700P12 – Professional Overview
The TCI Auto Automatic Transmissions 371700P12 belongs to TCI Auto’s 4X Four-Speed transmission package range. Rather than being a standalone transmission assembly, this product is configured as a complete application-oriented package for externally balanced Small Block Ford engines with a 28 oz. balance.
The package uses a non-electronic 700R4-based automatic transmission, giving compatible Ford applications access to four forward gears and overdrive without requiring an electronically controlled transmission system. TCI designed the 4X range to make adaptation between different engine and transmission platforms more straightforward by incorporating application-specific components into the package.
With a 550 horsepower capability, the 371700P12 is positioned for performance-oriented street applications where overdrive, automatic operation, and engine compatibility are important considerations. It is particularly relevant to restomod builds, street rods, classic Ford projects, and other compatible Small Block Ford applications.
Compatibility and Application Details
The 371700P12 is specifically associated with externally balanced Small Block Ford engines using a 28 oz. balance. The package is supplied with a corresponding flexplate configuration and an SBF bellhousing to simplify the connection between the Ford engine and the GM-style 700R4-based transmission.
This configuration is particularly useful for builders who want the packaging and driving characteristics of a four-speed automatic overdrive transmission while retaining a compatible Ford small-block engine.
The package has also been identified for applications involving Ford engines such as the 289, 302, and 351W, although final fitment should always be confirmed against the exact engine, chassis, balance configuration, driveshaft arrangement, and other vehicle-specific requirements.
The transmission uses a constant-pressure valve body, which is designed to reduce the sensitivity associated with conventional TV-cable tuning on 700R4-based transmissions. This makes the 4X design particularly relevant to street-oriented builds where consistent automatic operation is important.
Transmission Design and Performance
At the heart of this package is a non-electronic 700R4-based transmission with four forward speeds. Its gearing includes a 3.06 first gear, followed by 1.63 second, 1.00 third, and 0.69 fourth gear ratios. The overdrive fourth gear helps reduce engine speed during cruising compared with a conventional three-speed automatic.
The transmission is rated for up to 550 horsepower, making it suitable for appropriately matched street-performance applications. Its automatic valve body provides conventional automatic operation, while the four-speed layout adds the benefit of overdrive for highway-oriented driving.
The package is also lockup compatible, providing another advantage for street applications where controlled torque-converter operation and efficient cruising are desirable.
What Is Included in the Package
One of the key advantages of the 371700P12 configuration is that it is supplied as an application-specific package rather than requiring the buyer to source every adaptation component separately.
The package includes an SBF bellhousing and a 28 oz. externally balanced flexplate designed around the intended Small Block Ford application. Available product information also identifies a pilot adapter, TV cable, dipstick, transmission cooler, and related installation hardware as part of the package configuration.
The transmission itself uses a steel transmission pan with a chrome finish and an aluminum case with a gray finish. The transmission has a 6-inch tailshaft and uses a slip-on yoke configuration.
Because the supplied components are matched to the intended engine configuration, buyers should verify the exact engine balance and application before ordering.
Technical Specifications
| Specification | Details |
|---|---|
| Brand | TCI Auto |
| Part Number | 371700P12 |
| Product Type | Automatic Transmission Package |
| Product Line | TCI 4X Four-Speed Transmission Packages |
| Transmission Type | Non-electronic 700R4-based |
| Number of Gears | 4 |
| Application | Externally balanced Small Block Ford |
| Engine Balance | 28 oz. |
| Bellhousing | Small Block Ford |
| Valve Body | Automatic, Constant Pressure |
| Advertised Horsepower Rating | 550 HP |
| Lockup Compatible | Yes |
| Torque Converter | Not included |
| Flexplate | Included, 28 oz. |
| Input Spline | 27 |
| Input Shaft | Hardened steel |
| Input Shaft Style | TH700R4 |
| First Gear Ratio | 3.06 |
| Second Gear Ratio | 1.63 |
| Third Gear Ratio | 1.00 |
| Fourth Gear Ratio | 0.69 |
| Tailshaft Length | 6.000 in. |
| Yoke Style | Slip-on |
| Transmission Pan | Stock |
| Pan Material | Steel |
| Pan Finish | Chrome |
| Case Material | Aluminum |
| Case Finish | Gray |
| Fluid Included | Yes |
| Fluid Quantity | 2 qt. |
| Dipstick | Included |
| Transmission Cooler | Included |
| Transmission Controller | Not required for non-electronic operation |
| Trans-Brake | No |
| Remanufactured | No |
| Quantity | Sold as a kit |
| UPC | 788120162319 |
Why This Four-Speed Package Is a Strong Choice
The main advantage of the 371700P12 is its combination of Small Block Ford compatibility and 700R4-based four-speed overdrive operation. Instead of adapting a generic transmission to the engine independently, the package brings together several components specifically intended for the application.
Its 550 HP rating gives it useful headroom for many performance street builds, while the 3.06 first gear provides a substantial starting ratio for acceleration. The 0.69 fourth gear, meanwhile, gives the transmission a meaningful overdrive ratio for highway cruising.
The non-electronic configuration is another important consideration. For builders who prefer a mechanically controlled automatic rather than an electronically managed transmission, this package provides a suitable architecture while retaining the benefits of four forward gears and lockup.
The constant-pressure valve body is also intended to address one of the common concerns associated with 700R4 installations: TV-system calibration.
Who This Transmission Package Is Best For
The 371700P12 is best suited to classic Ford builders, restomod owners, street rod enthusiasts, and performance-oriented vehicle projects using a compatible externally balanced Small Block Ford engine.
It is especially appropriate when the goal is to combine a traditional Ford engine with a GM-style 700R4-based automatic overdrive transmission without relying on a fully electronic transmission control system.
This package can be particularly attractive for builds using 289, 302, or 351W engines where the required 28 oz. external balance is present. However, the complete vehicle configuration should be verified before purchase because driveshaft, crossmember, shifter, and other chassis-related modifications can vary between vehicles.
Key Product Details for Buyers
The 371700P12 is not simply a replacement automatic transmission. It is an engine-specific transmission package designed around a particular Small Block Ford balance configuration.
Its four-speed layout, lockup capability, 700R4-based design, 550 HP rating, and included 28 oz. flexplate make it a well-defined option for compatible applications.
The package’s non-electronic architecture also distinguishes it from electronically controlled 4L80E-based transmission packages in the broader TCI 4X range. Buyers should therefore select the package according to both engine configuration and desired transmission control strategy.
For customers comparing options, it can be useful to explore the broader automatic transmissions collection alongside related performance transmission packages and complementary drivetrain components to identify the configuration that best matches the vehicle.
Ordering and Fitment Support
Before ordering, confirm the engine family, external balance specification, transmission requirements, and vehicle configuration. For this particular package, the 28 oz. externally balanced Small Block Ford application is an important fitment consideration.
Product identification can also be confirmed using manufacturer part number 371700P12 and UPC 788120162319.
If you are replacing an existing transmission or converting a classic vehicle to four-speed overdrive, providing the engine, vehicle year, model, and current transmission information can help establish whether this configuration is appropriate.
Frequently Asked Questions
What is the TCI 371700P12 transmission?
The TCI 371700P12 is a 4X Four-Speed automatic transmission package based on a non-electronic 700R4-style transmission. It is designed specifically for externally balanced Small Block Ford engines using a 28 oz. balance and is rated for up to 550 horsepower. The package includes application-specific components to simplify the Ford-to-transmission installation.
What engines is the 371700P12 designed for?
The package is designed for compatible externally balanced Small Block Ford engines with a 28 oz. balance. Product information specifically references engines such as the 289, 302, and 351W. Exact fitment should still be confirmed based on the complete vehicle and engine configuration before purchase.
How much horsepower can the TCI 371700P12 handle?
The 371700P12 has an advertised capacity of up to 550 horsepower. That rating should be considered alongside the vehicle’s intended use, engine characteristics, torque output, and overall drivetrain configuration when selecting a transmission for a performance application.
Is the TCI 371700P12 electronically controlled?
No. The 371700P12 uses a non-electronic 700R4-based transmission with an automatic valve body. Its configuration is intended for applications where a mechanically controlled four-speed automatic is preferred over an electronically controlled transmission.
Does the 371700P12 have overdrive?
Yes. The transmission has four forward gears, with a 0.69 fourth-gear ratio providing overdrive. It is also lockup compatible, making the configuration well suited to street vehicles that require both performance gearing and more relaxed highway cruising.
Does the package include a flexplate?
Yes. The 371700P12 package is supplied with a 28 oz. externally balanced flexplate intended for the specified Small Block Ford application. This is an important part of the package because the engine’s external balance must correspond to the supplied flexplate configuration.
Is the 371700P12 suitable for a restomod or street rod?
Yes. Its combination of four-speed overdrive, automatic operation, lockup capability, and Small Block Ford compatibility makes it particularly relevant to restomod and street rod projects. The final suitability depends on the engine balance, vehicle configuration, drivetrain layout, and other fitment requirements.
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