The 915 Maincase also suffers the same problem with the bores for the roller bearings being "shagged" out of round, initiating all the same problems seen on the pinion bulkhead, although primarily, increased gear wear, increased oil temperatures and short bearing life.
We have chosen to use aerospace grade aluminum for the insert in the Maincase, machining a pocket and shrink fitting the bearing bridle in much the same way as the Pinion bulkhead work.
The original Maincase bulkhead bearings were an expensive Porsche only; modified bearing that uses a double retaining ring system to retain them into the case. These bearings now cost over $100 each, so WEVO have used the opportunity to revise the bearing style to be retained by tabs – a typical convention on racing transmissions.
The use of the tabs allows for less costly bearings (under $50 each) that has the same quality as the OE bearings. It also allowed us to have more structural material in the critical bridge area between the two bearings.
The Maincase is final machined with blue printed bore locations, bearing interference, shaft spacing, deck flatness and perpendicularity.
The alternate bearings are available from Windrush or by quoting the following part number to you local bearing traders. N305EC and NU2206EC, the first number being for the input shaft bearing, the latter for the pinion shaft.
All new studs installed.
The Maincase modification suits all 915 transmissions 1972 through 1986 magnesium or aluminum and 930 transmissions.