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Old 03-18-2019, 10:45 PM   #1
alexiskai
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Default Shift lever and fork size - absolute or relative?

Took my shift lever and forks to a machine shop to have the wear points welded up. Got them back and it looks like the ball is .472 and the forks are .480 and .483. I know the official numbers are .490 and .493-.5. The fit between them is good, no binding, but I wanted to check with you folks to see if I need to worry. Is there a reason the ball needs to be .490 or is it enough that it's smooth and round and fits the forks cleanly?
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Old 03-19-2019, 12:13 AM   #2
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Default Re: Shift lever and fork size - absolute or relative?

Quote:
Originally Posted by alexiskai View Post
Took my shift lever and forks to a machine shop to have the wear points welded up. Got them back and it looks like the ball is .472 and the forks are .480 and .483. I know the official numbers are .490 and .493-.5. The fit between them is good, no binding, but I wanted to check with you folks to see if I need to worry. Is there a reason the ball needs to be .490 or is it enough that it's smooth and round and fits the forks cleanly?
Relative, to a degree.

Look at it this way. Strive for absolute, but at the end of the day, getting it as close as you have it, I would probably call it good. You don't want the shifter to be so sloppy that it gets stuck in between gears or that it pops out of gear while you are driving down the road. You also want to put back enough metal to allow for future wear. That being said, many a shifter after 90 or so years are still going strong with lots of wear.

How far off were they originally?
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Old 03-19-2019, 01:57 AM   #3
alexiskai
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Default Re: Shift lever and fork size - absolute or relative?

I didn't measure at the time, I actually just got digital calipers while it was in the shop. But I think what happened is the ball is mostly the same size, just rounded off, while the forks have been built up to fit the ball. Wear was noticeable on the forks more than the ball when I disassembled the tower. The original symptom was difficulty getting into 2nd and 3rd gear.
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Old 03-19-2019, 07:49 AM   #4
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Default Re: Shift lever and fork size - absolute or relative?

Hard way to fix it. Would have been easier (cheaper?) to build up the ball to beyond the groove wear on the forks, make it round, and then mill out the forks to fit the ball.

I think it will work but will be "sloppy." You have up to 0.010 slop whereas the original fit was more like 0.003 - which is consistent in machining circles as a "sliding" fit.

I would give it a try. If that doesn't work bring only the ball back and have them build that up leaving the forks the size they are.

The problem for the machinist is in making the ball "consistent" at different angular approaches: the forks stay planer, the ball approaches the forks at differing angles. If the machining is not "round" then the ball jams in the slot at the end of the travel.

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Old 03-19-2019, 08:46 AM   #5
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Default Re: Shift lever and fork size - absolute or relative?

Thanks, I'll install it this weekend and then report back. It'll be an improvement over what I had and that's the only reference point I know.
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Old 03-19-2019, 01:12 PM   #6
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Default Re: Shift lever and fork size - absolute or relative?

There was a posting here some years ago by a guy that detailed his own method for restoring the shift lever. He built up weld on a worn ball and filed it by hand to a rounded but slightly squarish shape that loosely fit the corresponding openings in the forks. He claimed it worked just as well without the effort required for returning the ball to a perfect spherical shape. I did a mock-up of this method in an old junk transmission using J-B weld in place of the real thing. I used some Prussian blue and a Dremel to effect a smooth fit and was surprised how well it worked. I was even able to perform this test without having to remove the lever from the shift tower. I know this is kinda outside-the box, so feel free to let the bricks fly.
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