Quote:
Originally Posted by Joe KCMO
The 1939 to 1948 Ford and Mercury Shop Manual page 261 states backlash should be checked on the splines of the pinion shaft. Never greater than 0.008” and more than 0.003”. At 0.005” you are golden right smack center. Hope this helps. I have been looking for these numbers.
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That is the way to do it. I have a large Ford literature library I inherited from my dad. There is one piece of literature I have, and I don't remember which one it was that I finally found the specs above, checked at the pinion spline. The old-timers told me the way they used to do it when they didn't have the specs was .001" for every inch of ring gear, to allow for expansion between the gears. That method is usually pretty close to what the specs are the ancient Model T guys said the thickness of a business card between the teeth. I always end up fiddling with the allowable range of backlash trying to get the best pattern.
A rebuilder of 9-inch rearends, that's all he does for a living, told me that the Artist canvas yellow oil paint from Hobby Lobby makes the best gear marking pattern compound he has ever used. I haven't tried it yet.