8620 heat treated gears?

[Crosley.In.AZ]

I was looking at a set of ford 9 inch gears (new) on ebay at a budget price .

Listed as 8620 heat treated material.

i do not enough about different metals to know if these are OK or bad.

I know the gears we use in power glides are 9310 heat treated material and they hold up very well

[zzebby]

Tony, you only  need the hard high strength steel if you are pushing mega horsepower and exceed the yield of the material.  There are a lot more problems with gears that are not cut correctly and wearing prematurely.  I bought a set of new 9 inches 3.70  gears from US Gear and they are noisy.  I've reset / rechecked them twice and so has the shop I bought them at.  It is just the way they are.  A lot of guys I've talked with prefer original Ford gears...even if they are very old or lots a miles they are quiet (silent) and don't break if set up correctly.

[unklian]

8620 is case hardened, not hard all the way through.

It's good stuff, in the right application,
can be used for gears and camshafts.

[kb426]

As I remember from the old days: (scarey at best) 8620's were what was originally sold for drag racing. They are hard and somewhat brittle. The 9310 series have higher impact loads but won't last on the street. So my thought is for low hp applications, the 8620 is the best and the 9310 is for high hp applications. I would run 8620's on the street and think I was doing the right choice.

[Crosley.In.AZ]

thanks for the answers.

Noise is not a concern, these will be used for a drag car.  Not too much HP and the weight will be about 2700 or so

If I buy the gears, I may send them out for cyro treatment