Craig’s Automatics

Performance FAQ

What is a Shift Kit?

A Shift Kit, or the like, is designed to quicken up gear changes (the actual time taken when changing from gear to the next usually felt as a kick in the seat) and modify the shift points (when the gear shift happens). All this usually happens within the Valve Body. The kit achieves the above by removing oil restrictors, fitting of different weight springs and bypassing or locking out certain valves.

What is a full Manual Valve Body?

Full Manual means that the valve body has had all the automatic gear shifting functions removed. Every gear shift must be made by the driver. The valve body will attempt to engage the gear selected regardless of road speed and engine rpm.
A Forward Pattern Full Manual Valve Body (3 Speed) would have a shift pattern as follows:
A Reverse Pattern Full Manual Valve Body (3 Speed) would have a shift pattern as follows:

How do Transbrakes Work?

The Transbrake operates by bringing on another clutch pack (usually Reverse) within the transmission. It stops the transmission from transmitting power to the back wheels. This allows the driver to apply full engine throttle without fear of the vehicle creeping forward as is common when trying to hold the car using the foot brake.


There is no vehicle creep and usually faster reaction times.


Are whilst the car is stationary on the Trans brake; that entire engine HP is being converted into heat. It doesn’t take long for a big HP engine to boil the fluid inside the torque converter.

The other main disadvantage is the shock experienced by the driveline when the Transbrake is released.

How is a Transbrake activated?

In most cases the Transbrake is activated by an electric solenoid and only in first gear. The driver activates the solenoid via a button. Whilst the button is depressed the transmission cannot move forward. Release the button and you’re off.

Why increase the number of clutch plates?

The more clutch plates, the greater the frictional surface area. The work load when changing gears is now spread over this larger area. The same principle applies to vehicle braking systems.

Why use Kevlar and/or Carbon blended Bands/Frictions?

Kevlar, along with Carbon, has excellent heat resistance properties. The brake bands and clutch packs inside the transmission apply and grab moving components. The slowing down of these components through primarily oil friction causes heat (more on the 3 phases of Band/Friction apply in a later article). The higher the engine HP and rpm, the more work these friction components do.

The most common friction lining is actually paper based. These provide the best “bite” and aid in shift feel. Unfortunately they also discolour and burn easily. Once this happens they have lost their “bite” and the problem now compounds itself. Less bite means more slip which creates more heat further reducing the “bite” and so on. Kevlar and Carbon lined bands are really paper/Kevlar/Carbon composite bands that now have better heat qualities with a slightly reduced “bite”.

Why use Billet Servo/Piston Assemblies?

All bands are applied via a Servo/Piston set. These sets have a particular size that the factory deemed would provide good shift quality along with durability.

Oil pressure is measured in pressure per area (i.e. Pounds per Square Inch- PSI).
By increasing the Servo/Piston size we can get more clamping force on the band.

A secondary effect of increasing Piston apply size is the changing of the apply/release ratio.

What’s the go with Billet Shafts and all the different names/terms?

Most factory shafts are made from Carbon steel, also called plain carbon steel. These are a soft iron-based metal containing carbon, small amounts of manganese, and other elements. These shafts are Induction Heat Treated. In this process the shafts are heated by passing through a red hot coil followed by quenching in water. This creates a hard outer shell which is able to transmit modest amounts of engine torque. However the cores of the shafts are only able to transmit small loads.

The two other factors that have the greatest effect upon shaft strength are the overall length of the shaft and the shaft thickness at its thinnest point. With weight, space and cost now critical design features, manufactures are trying to do more with less.

Steels that contain specified amounts of alloying elements – other than carbon and the commonly accepted amounts of manganese, copper, silicon, sulfur, and phosphorus – are known as alloy steels. Modify the types and quantities of alloying elements and we get High-Strength steels.

The most common High-Strength Alloy Steel is 4340. Modifications of this base Alloy result in trade-marked names such as Hy-Tuff and 300M (4340 VAR or Vacu Melt).

There is one more material that has been especially designed for high torque loads. It is a maraging material that contains 18% nickel, along with appreciable amounts of molybdenum, cobalt, and titanium, and almost no carbon. It is traded under the name VASCO, very expensive, difficult to heat treat however will provide excellent torsional capabilities with short length, small diameter shafts.

Heat Treating/Hardening

Heat Treating can gain strength benefits for several reasons.

  1. It can stress relieve internal tensions locked inside components:
  2. It can add strength if the component was not originally treated i.e. Nitrating.

Cryogenics is also a form of Heat Treating (the absence of). This new science can stress relieve previously Heat Treated components.