Triple Gear Shafts

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Model T Ford Forum: Forum 2008: Triple Gear Shafts
Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson on Sunday, January 25, 2009 - 11:12 am:

I'm sure this has been discussed before but I've got to bring it up again. What is the point of making the triple gear pins oversized? Do any of the vendors sell the correct size pins. The new pins I've been getting are .679 in diameter where the bushing rides but should be .677. The thing that really irks me is the pin area that get driven into the flywheel is .684 and will break a flywheel if not reduced in size. I found that one out the hard way, once. I've yet to see a flywheel worn in the area the shaft is driven and if it was it would probably need more than a few thousands oversize shaft. I've also never seen triple gear bushings that could be reused. So what is the point. Why can't they be made to the correct size???


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith on Sunday, January 25, 2009 - 12:31 pm:

Read the Ford Service Manual. It clearly states, new shafts will be .003" larger.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Adam Doleshal on Sunday, January 25, 2009 - 01:38 pm:

The original pins are a press fit in the flywheel. When you remove them, you need to use replacement pins that are a few .001" larger than the original ones you pressed out so that you still retain the "proper" press fit (because the holes in the flywheel were enlarged a bit by the press fit of the previous pins).
Actually, if you have previously replaced your triple gear pins and then need to replace them again, you should actually use pins that are slightly oversize of the ones you used last time. I think that at one time, one of the vendors offered two oversizes of triple gear pins for this reason, but don't know if they are offered in any catalogs anymore. OVERSIZE SHOULD REFER TO THE SIZE OF THE PART OF THE PIN THAT PRESSES INTO THE FLYWHEEL, not the size of the pin that the gear rides on, that surface should be the same on all pins whether they are listed as "oversize" or not.
As far as the flywheel being cracked; I have magnafluxed flywheels and found cracks into the pin bore areas that were not visible. These cracks will become visible when you press the new pin in. Odds are that if you notice a crack after you push the new pin in, the crack was likely there before and was likely not "caused" by the oversize pin. There is one pin that is very near a magnet bolt, which is in turn very near a dowel pin, and this is where 95 percent of all the flywheel cracks we have found are located.
As far as the size of the pins is concerned, I think there is more than one vendor manufacturing them currently, but surface finish is more important to me than size since the bushings have to be machined to fit the pins anyway (unless you are using an old reamer to do the job which I guess would present a problem).


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