Lock nut for transmission main shaft. Porsche 911 72-89 / 964 / 993 / 996 turbo / 997 turbo / GT3  ❭  99903403300

Lock nut for transmission pinion shaft - M30 x 1.5
The Genuine Porsche 99903403300 transmission pinion shaft lock nut is an OE M30 x 1.5 shouldered lock nut for selected Porsche manual gearbox applications, including 911 1972–1989, 964, 993, 996 Turbo, 997 Turbo and GT3 models. It secures key transmission shaft components and is ideal for gearbox rebuilds, transmission repairs or restoration using Genuine Porsche hardware.
Sold individually

Fits:
Porsche 911 - 1972 to 1989 (915 and G50)
Porsche 964 - 1989 to 1994
Porsche 993 - 1994 to 1994
Porsche 996 turbo - 2001 to 2005
Porsche 997 turbo - 2007 to 2013
Porsche 996 GT3 - 2003 to 2005
Porsche 997 GT3 - 2007 to 2011
Manual transmission

Diagram ref no 20

This nut is used in selected Porsche manual gearbox assemblies, including 915, G50 and later Turbo / GT gearbox applications where specified.

What This Part Does / Functions
•  Secures transmission shaft components in position
•  Helps maintain correct gearbox shaft assembly preload and alignment
•  Supports proper operation of the pinion shaft / main shaft assembly
•  Helps prevent loosening under drivetrain load and vibration
•  Provides correct OE Porsche M30 x 1.5 thread and shouldered nut design
•  Replaces a worn, damaged, previously removed or incorrectly reused lock nut
•  Supports correct transmission rebuild and gearbox service procedures
•  Maintains factory Porsche gearbox hardware specification.

Why Replace This Part?
Transmission lock nuts are critical gearbox fasteners. During gearbox rebuilds or shaft service, the original nut may be removed, disturbed, damaged or no longer suitable for reuse. A worn, distorted or incorrectly secured shaft nut can affect gearbox assembly, shaft retention and long-term reliability. Replacing it with a Genuine Porsche OE transmission shaft lock nut helps ensure the gearbox is rebuilt using the correct factory-specified hardware.

When to Replace This Part
•   During manual gearbox rebuild or overhaul
•   When servicing the transmission main shaft or pinion shaft
•   If the original nut is worn, damaged, distorted or corroded
•   If the nut has been removed during gearbox disassembly
•   During differential, gear set or shaft bearing replacement
•   If the original lock nut no longer secures correctly
•   When restoring a Porsche gearbox with correct OE hardware
•   Whenever Porsche workshop procedure recommends replacement after removal.

Where It Fits on the Car
This lock nut fits inside the manual transmission / gearbox assembly. It is used on the transmission main shaft or pinion shaft, depending on the gearbox type and application.

Installation requires correct Porsche gearbox tools, torque procedure and workshop specifications. This is a specialist transmission component and should be fitted by an experienced Porsche gearbox technician.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99903403300

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