So it seems the Allison is 3.1.  Perfect ratio for my wish list.  I don't
remember the angle the gears are cut at or if they a the compressed powder
gears GM uses on some of their trannys.  Compressed powder is supposed to be
more robust.  Sort of counter intuitive.

I used to work at a small company that developed the process for these
gears. They were in Michigan. The secret was the powered metal was tool
steel. It included a small amount of wax. They were pressed to the
desired shape in a high pressure die in a hydraulic press. The part
would break in your hands if you pressed too hard. It was about 17% or
23% larger as I recall than the finished part. They were placed on
graphite sheets for baking in a 3 stage vacuum furnace. It was large
enough to place a cube pallet in. The temp was just below the melting
point. The hard part was the vacuum. Before I worked there, I did not
realize  what a real vacuum was. These gears are actually stronger than
the non-powder gears. They used this same process to make the cutting
tool bit for the threads on oil well pipe thread cutters on the drilling
rig. Very hard stuff.

-dave


The draw back is they are brittle. Low impact strength.

Here is a powdered metal Ford ring gear bulkhead Tracy broke with a hammer blow.

I would much prefer machined gears.

Paul Lamar

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