For a long time Windrush have recommended the use of the 915.301.311.3R style 915 side cover. This later version of the side cover had the highest stiffness and offered the highest performance solution for managing the seperation load of the Crownwheel and Pinion gear assembly. The earlier aluminum and magnesium side covers - while lighter - is less stiff and prone to cracking and failure under extreme conditions. Once quite inexpensive, the 915.301.311.3R have become more costly and difficult to obtain as a new replacement part.
Windrush elected to produce the XT-100 Side Cover, a billet side cover with the stiffness of the 915.301.311.3R and the additional benefit of a larger differential carrier bearing on the cover side - copying the bearing configuration of the 930 transmission.
The kit does not includes the bearing that is a standard Porsche part # 999.059.064.00. (Bearing can be purchased seperately).
This side cover can be used with any 915 transmission from 1972 - 1986 except those with the side cover oil pump installation.