Th400 Kickdown Switch Ki

The Th400 Kickdown Switch Kit by B and M AUTOMOTIVE is a precision transmission control component engineered for serious hot rodders, street machine builders, and mechanics who demand responsive gear selection during high-performance driving. This kit addresses a critical gap in vintage and modified TH400 automatic transmissions, where factory kickdown mechanisms may be absent, worn, or incompatible with modern carburetor setups. Whether you're restoring a classic Chevelle, building a street-strip cruiser, or retrofitting a TH400 into a custom chassis, this switch kit restores the automatic downshift function that maximizes acceleration and engine braking performance.

The kickdown switch operates by sensing throttle position through mechanical linkage, signaling the transmission control valve to command a forced downshift when full throttle is applied. This kit includes the switch assembly, mounting hardware, and springs necessary for proper installation and reliable operation under sustained load and repeated gear changes. The compact 5.4 x 1.25 x 7.65-inch package design allows for flexible mounting in tight engine bays while maintaining robust electrical and mechanical contact points. B and M AUTOMOTIVE's engineering ensures the switch functions consistently across idle, cruise, and wide-open throttle conditions without chatter or false engagements that could cause transmission shock.

Builders upgrading carbureted or fuel-injected engines with TH400 transmissions will find this kit essential for seamless throttle response and transmission synchronization. Installation requires basic mechanical aptitude and standard hand tools; carburetor linkage adjustment ensures smooth transition between the switch actuation point and engine load. This solution is ideal for street performance, bracket racing, and restoration projects where factory or aftermarket transmission controllers aren't practical. Proper setup eliminates harsh downshift shocks, improves launch characteristics, and extends transmission longevity by ensuring shifts occur at optimal engine RPM and load conditions.