MTFCA Forum

I recently pressed a set of pins out of a flywheel I was re-purposing. They looked pretty good so I cleaned them up and measured them. They are slightly tapered to the outer end. The worst one was .0025" down.
These are old originals with the small shoulder at the back so they don't come out.
If you were to reuse them in the absence of proper reproductions would you
a. Fit them with the wear on the outside of the pitch circle so the unworn side can take the load on the gears.
b. Linish the surface on which the bushing runs.
c. Just put them back in.

I know of superior replacements and triple gears with bearings. Sometimes though one can only do as needs must.

Allan from down under


Allan from down under.

I would do "a". But then I do have a bit of a reputation for doing hokey repairs from time to time?

A. If they still have a good press fit.

I use them to fill up my scrap drum.?

Save a couple Dan. They sometimes make good "pushers" in my workshop press.

I think I'll save them in case I ever have to tear down Henrietta.

Allan from down under.

They will work and you can resize them so they won’t have the very very slight oval shape. Just remember that you’ll ream the bushings for a perfect fit. So it would be a like new fit.

Once you press them out how do you keep them tight in the flywheel hole?

Dan, do you know if replacement pins were ever slightly over size to overcome that specific problem? I would expect the hardened pins to hold their dimensions, and the flywheel castings to be the weaker link. The original pins with the slight lip on the back end are not likely to come out on the gear side of the flywheel.

Allan from down under.

Allan, new pins are .004" larger at the fly wheel end to compensate.

Yes replacement pins are larger on the flywheel end. You only get the shoulder on one maker of pins that I know of. Those are the only ones I use.

One problem I am seeing is now you find flywheels that already have replacement pins in them. Dan

What do you think about to use Loctite by replacing new pins .

Toon

The issue is that there are at least two different makers of replacement pins, and BOTH are serviceable, one being slightly more pure in roundness than the other.

That said, let's stop for a moment and reflect. The original Ford design called for a 0.002"-0.003" interference fit between the raised pin area and the flywheel. So..yeah a purist approach would be to measure pins as received, and hone the flywheel out to achieve that value.

Purist? Well, there is a reason. Recall, well, near 20 years now, when Ford current transmission engineering decided on the T-100 project that the original design was a hope and a prayer and they could do a much better tranny internal than the original for the T-100? What happened? The T-100's kept swallowing transmissions and to the best of my knowledge have all been converted to the original design using standard replacement parts. I've run the numbers on that press fit mentioned above. I've even had one or two of my staff engineers rerun the numbers. Guess what?

At anything more than 0.003" and before 0.004" the iron in the flywheel is susceptible to radial spider cracking at the pin holes. No safety factor, all gone. Yeah, I know, lot's of guys will say they go for 0.006" interference and they get it and have yet to witness any spider cracking after a rebuild. My response to that? Continued Good Luck!

Going back again...a pin spins in the flywheel because the bush locked up both on the triple gear and on the pin! What lets go is then the interface pressure at the flywheel...better that pie shaped chunks grenade-ing through the hogshead! More interference is not the answer.

IMHO, Loctite would help the cause if all else is the same and some of it stays on press-in. I'll share but warn that I have never done this yet. I have actually thought of grub screwing the pin to the flywheel using the smallest grub I can get away with at one location per pin, and then using both the built in urethane 'dot' AND heat soluble Loctite on the grub as the where all to beat all and be done with it. Just tossing it out there...