Longfield FJ80 Gun Drilled 24-Spline Birfield The Longfield FJ80 Gun Drilled 24-Spline Birfields are made out of 100.0 percent chromoly and are precision polished to remove any imperfections that may cause stress risers. The internals of the birfield are also made from 4340 chromoly and are dual heat treated for superior strength.
The birfield has a M8 grease zerk at the end of the stub shaft and is gun drilled through the center of the birfield to allow for grease to pass through the zerk fitting and into the internals. This will save you precious time by eliminating the need to disassemble your axle just to service your birfields.
The FJ80 Gun Drilled 24-Spline Birfields also have a shallow relief near the splines on the stub shaft known as a Machined Spline Saver. The Machined Spline Saver eliminates stress concentrations caused by grooving from the tool that makes the splines on the stub shaft.
The stress concentration from the spline groove is a common failure point on birfield stub shafts. The stub shaft of the Birfield has dual snap ring grooves to accommodate FJ80s with short and long drive flanges.