72 Shift Cog Regrind. Possible?

[tomoco]

I've got one of those legendary '72 Electric shifts. 65 hp. Runs like a top. But no reverse. I pulled it apart and found that shift cog, and the reverse gear with the rounded edges. I think if I could find these parts they would cost a lot. So why not just repair these. So I carry it off to a machine shop, and he says, "we can't grind these. It's hardened steel."
I say, OK, Bye.
Then I get home and get out the Dremmel, and take it to a corner of the cog. I fairly easily ground a little notch into a meaningless corner. I could do this myself! might be a little tricky keeping both sides even -- hitting at the same time. But then, how much time do I spend in reverse?
Should I try this, or am I crazy?

 

[F_R]

Re: 72 Shift Cog Regrind. Possible?

It's been done before. It will last a little while. You will be grinding away the case hardening, that is why the life will be hard to predict.

It's kind of unusual to have reverse that bad. It is held in reverse by hydraulic pressure. How is forward? Only a spring holds it in forward.

 

[tomoco]

Re: 72 Shift Cog Regrind. Possible?

Forward is in good shape.
I actually have two of these. The other is worse, in fact it's broken into about 8 pieces. This one is from the "new" lower unit I bought.

As for the hardening, I expect it is already gone.
I'm inclined to grind the Reverse side of the cog flat, to get rid of the "Klunking".
But I think I'll go ahead and try to grind it square.
I've not got a whole lot to loose.

It's a shame because it runs quite well. Has good compression.

Still, I think, come September, I'll be looking for a motor.

thanks!

 

[Bindernut]

Re: 72 Shift Cog Regrind. Possible?

If you "face" the ends of the clutch dog to straighten it out, you'll make it shorter than designed. That'll guarantee that it won't make good contact and jump even worse than before. Instead of the face, you'll have to machine the edges of the dog...making it narrower...to true it up.
The clutch dog is pretty much a lost cause to try and machine back into shape...spring for a new one, the cost is less than the time you'll stick into the rework job for just a little more life.

The gears on the other hand you might have a little better luck with if you are or know a good smithy. I've machined a couple sets of gears for lower HP LUs with pretty good luck. I used a 3/8" carbide cutter and a turret jig on the Bridgeport to true up the engagement surfaces. Afterwards, I spent a little time with the torch & quench tank and spot rehardened the fresh milled surfaces. Won't be quite as good as the original case hardening, but it'll be fine for another few seasons.