P/N 641531 Tach adapter

[GAHorn]

The mounting ears on these things are usually broken by un-evenly, overtightening the nuts which hold it onto the accy case.
This is usually the result of someone attempting to stop an oil leak in the area by excessively tightening against a damaged or previously-used generator gasket. (Sometimes a homemade gasket is too thick/soft and allows too much compression, resulting in the same error.)

Remember, there's no real oil-pressure involved at this location...merely a seepage of gear-case oil slung onto the tack drive spindle. Whenever replacing a generator, DO NOT CUT the new generator gasket at the tach drive adaptor "triangle". Install the gasket intact, including the tach adapator area. Also make certain to REPLACE THE (old) TACH DRIVE OIL SEAL any time the adaptor is removed. Old oil seals take a "set" against the spindle and will not reliably seal when re-positioned after removal of the adaptor.

Flat washer, then (new) lock washer, plain nut---evenly torqued....only snug sufficiently to engage the lock washer (not specified, but about 50 in lbs) ...and alternately similarly to automotive wheel lug-nuts or head bolts. (A "dab" of Permatex No. 2 on the flat surface of the adaptor will seal it to the gasket. Early assy's used fiber or nylon lock nuts with no washers, but these are difficult to torque evenly at such light settings. It's better to use the washers and plain nuts, IMO. If you worry about vibration loosening the nuts (not a problem really), place some sealant on the exposed threads on top of the nut.)

Good luck.