#1  
Old 08-09-2022, 04:20 PM
jd0n88 jd0n88 is offline
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Default Tooth Pattern

How does this look for tooth pattern? First time doing this, backlash set at .008.
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  #2  
Old 08-09-2022, 04:57 PM
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67drake 67drake is online now
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From what I see it looks pretty darn good. It would help if you applied more resistance to the pinion while turning the ring gear ( or vice versa), to clarify the pattern a little more.

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71' GTO -original 400/4-speed/3.23 posi
13.95 @ 102.1 on street tires @ 4055lbs.

‘63 LeMans- ‘69 400 w/ original transaxle. 2.69 gears.
  #3  
Old 08-09-2022, 07:58 PM
jd0n88 jd0n88 is offline
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Yeah I was trying to give as much resistance as possible using a wrench on a ring bolt and a socket on the pinion nut rotating back and forth.

  #4  
Old 08-12-2022, 10:41 AM
jd0n88 jd0n88 is offline
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I changed pinion shim from .039 to .035 and backlash from .008 to .006 just to see how the pattern changed. I don't really see a difference.
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  #5  
Old 08-13-2022, 09:43 PM
jd0n88 jd0n88 is offline
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I must be doing something wrong, changing pinion shims and backlash doesn't seem to change the pattern?

Here are pictures with .009 backlash
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  #6  
Old 08-13-2022, 09:46 PM
jd0n88 jd0n88 is offline
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here are pictures with .014 backlash. I thought just a few thousands difference made a big change in the patterns:
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  #7  
Old 08-13-2022, 10:04 PM
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Changing backlash doesn’t affect the pattern, just how easy it is to read. I set backlash from .010- .012 to check the pattern. When I get the pattern where I want it by changing the pinion shim, I put the backlash where I am going to run it on final assembly.

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71' GTO -original 400/4-speed/3.23 posi
13.95 @ 102.1 on street tires @ 4055lbs.

‘63 LeMans- ‘69 400 w/ original transaxle. 2.69 gears.
  #8  
Old 08-14-2022, 04:34 PM
mgarblik mgarblik is offline
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Actually, your pattern is changing quite a bit. Your first set of Pics was the best pattern by a long shot. First of all, your pics are mostly showing the "coast pattern", which is of secondary importance. The "Drive" side of the tooth is the convex side and the coast is concave. You don't want any sharp cutoffs in the pattern. A sharp cutoff is an area of stress concentration and a possible break point on the tooth. Your first set of pics have a nice start point off the toe of the tooth, and the end of the pattern has a nice fan out of the pattern toward the heel but still on the tooth where there is plenty of "meat". All your other patterns have sharp start and cut offs. In an early post it was suggested, that you load the ring gear more to get a cleaner pattern. That would be a great idea as well. apply load with a pry bar to the outside of the ring gear to the case so it takes 40+ ft. lbs to turn the pinion. That will clarify the pattern and move it toward the heal and make a better pattern. Turn it both directions to get a good drive and coast pattern. I think your first settings with .008" backlash looked pretty darn good. Here are a couple of pics of a 9.3" Pontiac rear i did recently.
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