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Discussion Starter #1
I just finished my rebuild of my dead 12 bolt. Installed 3.73 gears new strange center section. My question the pinion spacer needed to be .043 to get a good patern with .008 backlash. does this sound out of line?
Thanks.
 

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I think I would be okay with that. What did the old pinion have?
 

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I have never had a 12 bolt that needed a .043 pinion shim. Most are .034-.028. What does the pattern look like?

Are you trying to use the original side shims?

Have you tried a thinner pinion shim with different side shims? The pinion shim comes first. Get it right (based on pattern or a depth gauge) and worry about the side shims last.

Not trying to panic you but .043 seems like a bit too much.

You said you have a Strange center section. Is this a complete Strange housing? Is it a 12 bolt center section for a 9 inch Ford housing? If you have a different housing than GM disregard my comment about the shims.
 

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Discussion Starter #4
Ok lets start with the pinion shims. original was .030 removed 3.42 ratio changed to 4.56. Used synthetic oil Factory diff started acting strange. Decided to change to 3.73 and a new differential. Got a strange diff and 3.73 gears from Summit. .030 was what worked in the first change ( 4.56) So i started there. Worked up to .043 thats were im at.
 
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