TransGo Shift Kit – TH400 Transmission

This TransGo Shift Kit is designed for TH400 automatic transmissions and focuses on improving shift quality while addressing common valve body wear issues found in higher-mileage transmissions. Rather than simply modifying shift feel, these kits are engineered to restore proper hydraulic function inside the valve body and help extend the life of the transmission.

Inside an automatic transmission, the valve body controls hydraulic pressure and fluid routing for each gear change. Over time, internal wear and component fatigue can cause delayed shifts, inconsistent shift timing, or clutch wear. The components included in this kit are designed to correct those issues by improving hydraulic control and restoring the original operating characteristics of the transmission.

This kit is intended for normal driving and light-duty use, making it a practical upgrade for vehicles that see regular street use or occasional towing. Once installed, the transmission typically delivers more consistent shift timing and improved overall drivability.

Common Issues Addressed

This kit helps correct or reduce several common TH400 transmission problems, including:

• Delayed or soft gear changes
• Harsh or inconsistent 1–2 shifts
• Premature 3rd clutch wear
• Overly sensitive passing gear operation

What a Shift Kit Does

Shift kits include a combination of updated and redesigned internal components that install primarily in the valve body assembly. Depending on the transmission design, some components may also interact with the pump or other internal hydraulic circuits. These upgraded parts help correct design weaknesses and wear points that develop over time.

Typical components included in a valve body improvement kit may include:

• Springs
• Valves
• Check balls
• Gaskets
• Separator plates
• Additional small hydraulic components

When installed properly, these improvements help restore hydraulic integrity and can often allow a worn transmission to shift more consistently than it did before service.

Shift Kit vs. Performance Reprogramming Kit

This Shift Kit is designed primarily for durability and improved drivability in street-driven vehicles.

Performance-oriented reprogramming kits, by contrast, are typically intended for heavy-duty or racing applications and may include features such as manual shift control or more aggressive shift characteristics.

For most street vehicles, a standard Shift Kit provides the best balance of reliability, drivability, and improved transmission operation.

Fits:

• 1965-1979 Wagoneer
• 1974-1979 Cherokee
• 1965-1979 J-Series Trucks