The Bulletproof C4 Transmission

The Ford C4 medium-duty transmission can handle significant loads. It has become widely popular among enthusiasts and racers due to its ease of use, strength, and durability.

To identify a C4, look at its bolt pattern between tranny and bellhousing as well as its flexplate for its presence of 164 tooth ring gear and pan mounted dip stick.

The Bulletproof C4 Transmission

High Stall Torque Converters

Selecting an ideal torque converter for your street-and-strip vehicle is essential to its performance, even small modifications to engine or drivetrain can dramatically alter how a torque converter performs for you.

Torque converters serve two primary purposes, providing extra power when departing from a stop and maintaining engine rpm through gear changes.

Unfortunately, most stock torque converters don’t perform either of these functions very efficiently.

One way of comparing converters is to observe their flash stall rating, or RPM reached immediately after transbrake release at launch. Unfortunately, this measurement can be extremely hard to accurately gauge due to varying conditions like track conditions, tires, suspension and car weight all having an effect. To reduce variables we advise speaking to a dealer directly and providing them with details regarding your project goals – for the best results it’s always a good idea to bring this up with them before hand!

The Bulletproof C4 Transmission

High Stall Gears

The weight of your vehicle determines when its converter stalls; heavier cars cause greater load to move through its converter and cause it to stall at higher rpm, while lighter cars with lower numerical gear ratios tend to cause it to stop working sooner.

The speed at which a vehicle’s transmission engages second gear also has an effect on converter stall. Performance and race engines tend to generate most of their torque above 1,100rpm; using an inefficient converter with such engines would be wasted performance and lead to excessive heat build-up in its fluid.

Street driven applications should opt for a moderate stall (below 2800). This will allow the engine to reach its peak powerband at an ideal rpm and launch performance while also keeping torque converter slippage under partial throttle to a minimum. Too low of a stall could leave your car slow off the line; too high a stall might result in excessive high gear slippage adding time to your ET time.

The Bulletproof C4 Transmission


Transbrakes provide drag racers with an invaluable tool for building up speed prior to racing, which allows them to gain an edge by being able to launch with higher engine revs than their competition.

Transbrakes also help keep engine internals from revving too high and overheating, which could damage transmission components during mid-shift. Many C4 racers utilize rev limiters in addition to transbrakes; just be careful not to over-rev your engine or it could explode!

Transbrakes are essential upgrades for race cars with high-rpm powerplants. When installing one, be sure to place its activation button somewhere it will be easy and quick to access; many racers opt for transbrake setups with delay boxes to speed reaction time further.

The Bulletproof C4 Transmission


Ford produced the C4 light-duty automatic from 1964 through 1981 and became popular among drag racers due to its simplicity and reliability. It was designed as a replacement for their Ford-O-Matic two speed automatic in smaller Ford vehicles.

Internals of the TCI C4 differ considerably and are tailored more toward racing applications. A six-pinion planetary gear set offers significant improvement over its three-pinion predecessor. Furthermore, an external transbrake solenoid provides faster cooling when operating at full throttle than its internal counterpart would.

A blended pan-fill bellhousing attaches to its case using a seven-bolt pattern instead of five for additional strength, making it essential for street and weekend racing applications with high RPM applications that risk fluid starvation.

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