5. Tuner Category - Transmissions/Differentials/Transfer Cases

All the stuff that was approved in Sport Category, plus in Tuner Category, you can have mechanical Limited Slip Differentials (LSD), and replace final drive ring and pinions with alternate parts as long as the final drive ratio isn't changed from OE.

You can also use an aftermarket pressure plate and clutch disk as long as they are both the same diameter and design as stock; so no multi-puck clutches unless your car came with it from the factory. You can replace the flywheel as long as the diameter and material are the same, so you can't put an aluminum flywheel in place of a steel one.

Differential bushings and transmission mounts can now be replaced, as long as they are the same material as stock (solid metal is a no-no).

Tuner Category Transmissions/Differentials/Transfer Cases - Full Rules

1. Limited Slip Differentials (LSD): Any mechanical LSD unit is permitted. Final drive ring and pinion gears may be replaced with alternate parts, provided the final drive does not change.

2. Any mechanical shift linkage may be used.

3. Any clutch disc and pressure plate of stock diameter and design may be used, provided that they can be bolted directly to an unmodified stock flywheel.

4. Alternate flywheels are permitted. Flywheel material shall be the same type as OE and the ring gear diameter must be the same as the OE flywheel.

5. Any transmission mount is allowed provided it attaches only to the original mounting points, does not relocate the transmission (other than incidental to changes in compliance material), and weighs no less than the OE mount. The amount of metal in a replacement bushing may not be increased relative to the amount of metal found in a standard bushing for the particular application. Solid metal bushings are specifically prohibited. All components between the transmission and the mounting structure are considered to be part of the mount assembly.

6. Differential mount bushings may be replaced but must attach in the standard location(s) without additional modification or changes. Differential position may not be changed. The amount of metal in a replacement bushing may not be increased relative to the amount of metal found in a standard bushing for the particular application. Solid metal bushings are specifically prohibited.

7. Electronic Transmission/Differential Control

1. The Transmission Control Unit (TCU) may be re-programmed. This allowance only applies to modification of transmission behaviors and does not extend to re-programming any other components.

2. Electronic differentials may be re-programmed. This allowance only applies to changing differential behaviors and does not extend to re-programming any other components.

Sport Category Transmissions/Differentials/Transfer Cases - Full Rules

1. Transmission and differential coolers and lines may be added.

2. Shifter bushings may be replaced; non-metal bushings may not be replaced with metal bushings.