Looking for anyone that has information about the names of the manufacturers and types of differentials used in the Durant cars. Who built the differentials and what years did they manufacture them for Durant? What types with their part numbers were used in the various Durant models?
It could have been any number of companies. Durant owned one or more himself and previously had added some to General Motors. Timken, Dana, Eaton, Hyatt, etc. are well-known. They usually bought up the lessor competitors.
Generally, the gears would have been straight bevel gears. If they had a twist to them, they'd be called spiral bevel gears.
Hypoid rear ends were introduced by Packard, I think after Durant was gone.
There was almost a monopoly in bevel gears by The Gleason Company. Brown and Sharpe also made bevel gears. There is or was a European type as well. Rather, I should say, they built the machines to make gears and also calculated the formulas and settings for the machines to produce the desired gears. In addition, they built grinding machines and inspection machines.
It is possible that some firm could make prototype bevel gears using edm machines.
Gears require the best machines, the best machinists and the best materials. They are thus very expensive. The few producers that are left have a struggle. The international trade agreements seem to be divvying up the business between cheap Asian sources and high-priced European sources. In the US, the military is partly responsible for keeping some capability alive. Up until recently, it was required that military parts be produced in US facilities. The thought was that taxpayers should expect the jobs for their own families, rather than overseas. That may be weakening.