Shim for Used 8 3/4 Gears

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72DMag

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I purchased a slightly used ring and pinion from a friend. Only had handful of passes on them. However after reviewing Mancini's guide for installation I am unsure how to determine what size shim should go under the pinion bearing. He removed the bearing and shim and threw them away. Also no paint was marked on the ring gear. According to the guide without that if I don't get the wear pattern correct premature failure will occur. Maybe they are a little too critical in the guide.

Anyhow can I use the ring and pinon and how do I determine which thickness shim should be placed behind the pinion bearing? thanks!!
 
Is nothing engraved on the end of the pinion gear? There is a way to check it with a mic off a bar across the bearing cap as that is about as close you can get to the centerpoint. Also you can take an old pinion bearing and polish the inside so it slips on the pinion and use that as the set up bearing so you dont have to press and pull the bearing off looking for the right shim stack. My US gear took .020 shim and it was marked on the end of the pinion as well as proven with the mic across the bearing cap method.

Here is a post explaining the cap surface method: I used a square chisel as a straight edge that measured exactly 1" square. imagine that!
"..You DON'T need high tech tools to do this. Aftermarket gears have the depth measurement marked on them. This number is the measured distance from the machined surface of the pinion gear head, to the centerline of the ring gear. Common sense tells you that the ring gear centerline, is also at the parting line of the caps. So my "trick" pinion setting tool is a precision straight edge and a set of dial calipers. Lay the straight edge across the carrier, place dial caliper on top of straight edge.....roll the caliper until the "tail" contacts top of pinion gear. Read that number, subtract width of straight edge(mine is exactly 1") and there you have it. This and a set of honed bearings is ALL you need.."
 
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@pishta Thank you!! I found this on the pinion. I didn't see anything on the ring gear. what does the 315N mean??

20200427_171743.jpg
 
The 315N is a match number, the ring gear should have the same number. The other number is the pinion depth. What I would probably do, is remove the old pinion, see if there are any depth numbers on it. Then see what shim is under the old bearing. That might help you determine what shim to start with
 
I found this on the ring. Its really faint and explains why I missed it. From what I can tell its 315N next line BL?? Then 006 then 010 maybe?? Hard to see them those make any sense??

20200427_175815.jpg


20200427_175839.jpg
 
The 315N matches it to the pinion, the BL will be a backlash setting. .006 sounds right. .006 to .010 might be the spec
 
Yup, you got it! 315N is set number. .006-.010 is nuts on backlash spec.
 
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