ERIE, CO.  80516




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GBox oiling system upgrade

The 996 Twin-Turbo gearbox was designed by Porsche for the stresses of the 400-450 horsepower factory engine and the g-forces generated by the stock chassis. Porsche recognized the limitations of a street gearbox in high-performance applications with the GT3Cup and the RSR. The g-forces that these cars generate, and the high rpm within the gearbox required Porsche to use a pressurized oiling system with external cooling (using a pressure-regulated mechanical pump driven by the pinion shaft). At high rpm, oil is thrown off the gears by centrifugal force, and under hard g-loading oil is forced into the differential housing. Using a pump to scavenge the oil out of the differential housing and a spray-bar to oil the gear-mesh allowed these gearboxes to survive the rigors of racing. When the engine is upgraded the gearbox must be upgraded. With 996TT engines producing 800-1000 hp the stresses on the gearbox exceed stock-design capability. Upgrading the oiling/cooling system and using more robust 997TT parts in the gearbox will allow it to handle the increased horsepower and torque. The GT3Cup/RSR pressurized oiling/cooling system can be fitted to the G96/50 AWD gearbox using Porsche Motorsport Parts.

The steps to install the GT3Cup/RSR oiling system are as follows:

The 'street' bell housing is machined to accept the oiling system parts. New replacement bell housings also must be machined.

machining 996tt bell housing

Passage machined for oil tube.

996tt oil tube passage

Bell housing machined for the pinion squirter.

996tt pinion squirter

Center section with oil pump provision (p/n 996 310 102 9A).

996tt pmna center section

Mechanical oil pump (with internal pressure regulator) (p/n 996 307 023 88), oil pump pinion drive gear (p/n 964 307 331 01), differential housing scavenge pickup (p/n 996 307 049 9A), spray bar (p/n 996 307 043 88).

996tt oil system parts

Motorsport tail-cover (p/n 996 301 301 9A) which requires additional machining for the 4wd application (bore for output seal and block off pinion oil gallery).

996tt pmna tail-cover

Scavenge pickup installed in the differential housing.

996tt differential scavenge pickup

Scavenge pickup mounting hole in billet retainer plate (p/n 996 302 121 9A GB), left.

996tt custom retainer plate

Oil pump installed in center section. 3/4 shift fork must be machined for oil pump drive clearance.

996tt center section with oil pump

Spray bar installed.

996tt gear-stack spray bar

Oil cooler and tail-cover installed.

996tt gearbox oil cooler

This oiling system upgrade can be performed on the G96/50 4wd gearbox, on the G96/90 GT3 gearbox and others, Additional upgrades include limited-slip differential, re-gearing with stronger 997TT mainshaft and up-rated clutch slave cylinder modification.

Please contact us with any questions about the process.