Transmission Parts & Upgrades

Submitted by on November 10, 2011 – 9:21 pmNo Comment



901-series transmissions were used in the 911 from 65 until 71. The last two years’ 901’s were known as 911 gearboxes since they employed a slightly different case that permitted the new 225mm “Pull-type” clutch. 901’s were also used in the 914/6.

These gearboxes work quite well for engines in the 2.0 litres to 2.4 litre sizes without significant modifications. We do recommend installing the aluminum intermediate plate in any 901 that will see any competition. This adds a good deal of strength to help support the shafts. For 2.7 litre engines and larger, we also recommend installing a cooler and pump. Race cars should also get a pressurized lubrication system that locates an oil jet at each gearset and the ring & pinion.

These transmissions can be regeared quite successfully for racing and street performance. Since 2nd gear is machined as part of the mainshaft, this entire part must be changed when replacing 2nd gear unless you use a 904 mainshaft. This special, racing part permits swapping any 904 2nd gear ratio without changing the shaft. Be sure to check out our video on the 915 here!


The 915 appeared in 1972 with a major upgrade in strength, compared to its predessor. The first ones didn’t shift as well as the later ones due to