So there I was with the heat at the ready, press at the ready and the gear just dropped off onto the bench!
This customer was very lucky that it didn't fail catastrophically and destroy the axle.
That's interesting. Notice it cracked right at the groove for the key! I wonder if that happened when the gear was pressed on?
Probably before the advent of radiusing the key way
I've a few old axles and saved them for the gears.
I can't recall seeing a cracked gear.
I had a problem pressing a gear on a new axle and found that the axle I had was at the top end of the allowable tolerance that Ford used when the gears and and axles were made.
The new axle I had plus using a axle gear that happened to be on the LOW end of the allowable tolerance and that was the problem. It was just to tight.
I have a feeling when the axles and gears were assembled on at the factory an assembler picked through the gears and found some that would press on fairly easy. They were tight of course but not so tight that you had to force them on.
That's the reason I think that some of the gears are really tough to press off more than others.
Maybe the gear was a really tight gear on the shaft plus cracking on the keyway line. Maybe?
I have learned to check the shaft size before pressing on gears ,some are too big at the gear end. ,ruined a new shaft that way luckily the gear did not break but the shaft bent and the metal scraped off when I removed the gear.
I got a replacement shaft from the vendor
So what are the proper dimensions for the axle and the gear? How much difference for a press fit are we looking for?
The vendor sent me a replacement shaft also. When I called him and after he checked his axle's there were a few that were right on the top end of the allowable limit like the one I had.
I don't remember what the measurement was but he did tell me that the vendor he used to make the axles went by the same specs that was on Ford's original print. I had already had the shaft micked by 2 machine shop instructors at the school I worked for to verify the dimension besides myself and they determined the same thing that I did.
As Lorenzo said, measure before you start to press the gear on the shaft.
Maybe someone who is a machinist could tell us what is an allowable press fit tolerance would be.