I have a NOS GMC ring gear that is still in the GMC box for a 56-59 GMC 6 cylinder.

https://plus.google.com/u/0/1126369...2151510882&oid=112636930370126476644

It has absolutely no chamfer on either side and there is no front for back to it. We put a lot of miles on our old GMC tank wagons in those days and we bought a new ring gear after we had used up the teeth on both sides. I never used any special precautions except that I used a big rose bud to get the ring gear hot before the heat transferred to the rear main and seal. When the entire ring gear was red, it only took a light tap and it fell off. I quickly flipped the gear, tapped it back on and let it shrink itself back on. I did this same procedure on my father in law's 1950 John Deere A a while back so we could sell it to go toward my mother in law's nursing home bill. The JD ring gear hadn't been off in 65 years and dirt had plugged up the drain hole and the ring gear had stood in water and mud for years.