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Recently finished putting together this 3.08 posi diff from a 67. I'm reusing the original, lower mileage gears with the original 0.023"pinion shim. The backlash was 0.016" before new bearings and was still the same after new bearings. Shimming is all same as original, except I moved the ring gear closer to the pinion by about 0.007", resulting in 0.008" backlash.
My question is regarding the patterns. Please take a look and let me know if these (used gear) patterns will work or, if not, what changes do I need to make. They seem fairly centered but favoring the toe, but they are wide and long.
Thanks in advance for any advice you can give.
Bill
Drive is full but low, indicating wear.
Coast is center to toe and appears to be equal but the pattern could be sharper.
67's had bad posi cases, prone to cracking. The case is stock.
016 lash is bad, 008 is good but the lash variance should be under 002" over 360* I don't know what you got.
I can't say if they will make noise or not, 023" pinion shim is not common for GM gears. While not impossible since the housing and posi case machining is always off, I don't recall an original GM vette gear set with a pinion shim under 025"
I hope you checked the ring gear bolt hole depths as many were shallow causing them to back out in use.
Thanks, Gary!
The pinion shim is .0227 to be exact. Gears are original dated 3.08 ratio.
Lash variance is .001 peak-to-peak at 4 places around.
Ring gear r/o is 1-1.5 over 360 deg. I cleaned the ring gear bolt holes thoroughly and the factory bolts would thread in all the way to the shoulder.
Used original bolts, split locks and red loktite @ 45 lbft.
Also, in lieu of going the best route of tuning the posi pack per your method, I used the factory manual procedure of checking spider backlash one side at a time and shimming the side gears to get .006 - .008 backlash in all 4 positions. This required adding .030 additional shim to each side gear. I’m using original posi pack, so does that mean they’re worn by .030?
I think I’ll go with what I have since things appear to be normal for the age and wear. This car won’t be subject to any harsh treatment as it’s a low hp small block.
Now to try to get the yellow paint cleaned out.
One last thing… put the axles in with nice, close fitting snap rings and I have .008 end play on one side and exactly 0.0 on the other. Not sure I’m comfortable with zero clearance.
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Ring gear pattern- Opinions please
