These are the part numbers for the two speed chevrolet vacuum shift assembly on 2 speed axles for 1956-1958 in order to rebuild it:
Diaphragm- 3847058 GM#
374451 Bendix#
Whole assembly- 3874330 GM#
2504299 Bendix#
Cylinder and Boss assembly- 3847055 GM#
374460 Bendix#
Shell and seal assembly- 3721330 GM#
377271 Bendix #
Piston rod seal- 3721328 GM#
374534 Bendix#
Diaphragm seal- 31/32 I.D.x1.5 O.D.x 7/32 Thick
GM# 3705847
Diaphragm assembly gasket- 3705848 GM#
Diaphragm felt packing- 3705845 GM#
Packing retainer- 3705846 GM#
Piston rod seal gasket- 3723038 GM#
377416 Bendix#
Piston rod- 3721350 GM#
377274 Bendix#
Many of these parts are still sitting in GM dealerships. I had my wife check with her parts guy, and the parts I needed were available, but scattered throughout the US. I would have to pay the shipping to get them to her GM dealership, so cost will be pricey. Hope this helps.
Turns out my diaphram was bad, so I just replaced that. Shifts much quicker now and easy.
