4th and 5th gear set for 901 gearbox. Porsche 911  ❭  90130291310

4th and 5th gear set for 901 gearbox - Can be used for 4th and 5th gear
This gear set fits inside the 901 gearbox on Porsche 911 models. It is installed within the internal transmission gear train for the 4th and 5th gear positions according to the factory gearbox layout.

Fits:
Porsche 911 - 1965 to 1971
For 901 gearbox

Available with different gear ratios - example - 31:22 (number of teeth on each gear) - 0.71:1 (gear ratio)

31:22 - 0.71:1 (Porsche code "ZD") 
29:22 - 0.76:1 (Porsche code "ZA")  
29:23 - 0.79:1 (Porsche code "Z")  
28:23 - 0.82:1 (Porsche code "Y")  
28:24 - 0.86:1 (Porsche code "X")  
27:24 - 0.89:1 (Porsche code "W")  
27:25 - 0.93:1 (Porsche code "V")  
26:25 - 0.96:1 (Porsche code "U")  
26:26 - 1.00:1 (Porsche code "T")   
25:26 - 1.04:1 (Porsche code "S")   
25:27 - 1.08:1 (Porsche code "R")  
24:27 - 1.13:1 (Porsche code "Q")   
23:27 - 1.17:1 (Porsche code "P")  
23:28 - 1.22:1 (Porsche code "O")  
23:29 - 1.26:1 (Porsche code "N")   
22:29 - 1.32:1 (Porsche code "M")  
22:30 - 1.36:1 

Diagram ref no 4 and 5

The 4th and 5th gear set forms part of the internal gear train inside the 901 gearbox. These gears transfer engine power through the transmission at higher road speeds, supporting smooth cruising, correct gear ratios, and reliable power delivery.

Functions
• Replaces the 4th and 5th gears in the 901 gearbox
• Supports correct transmission gear ratio operation
• Helps restore smooth higher-gear driving performance
• Transfers engine power through the gearbox
• Replaces worn, noisy, chipped, or damaged original gears
• Suitable for gearbox rebuilds and transmission restoration
• OE Match replacement for classic Porsche 901 gearbox repair.

Why Replace This Part?
Gearbox gears can wear, chip, pit, become noisy, or suffer tooth damage due to age, high mileage, poor lubrication, previous gearbox wear, or hard use. Worn 4th or 5th gears may cause whining, vibration, poor engagement, metal debris in the oil, or reduced transmission reliability. Replacing the gear set during gearbox overhaul helps restore correct operation and protects related transmission components.

When to Replace This Part
•  4th or 5th gear is noisy, worn, chipped, or damaged
•  Gearbox whine or vibration is present in higher gears
•  Metal particles or gear debris are found in the gearbox oil
•  The gearbox is being rebuilt or inspected
•  Gear ratios are being restored to original specification
•  Related synchro parts, bearings, or shafts are being replaced
•  The vehicle is undergoing Porsche 911 transmission restoration

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

90130291310

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