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GM 8.5 10 bolt. First time setting up gears, would like some advice

5K views 34 replies 4 participants last post by  lmsport 
#1 ·
installing a posi and gears in a 74 nova 8.5" rear end for my 69 nova. heres a picture of my pattern with .009-.010 baclash. the richmond gears call for .008. any help would be apreciated. i think i need to go a little thinner on pinion shim and tighten up back lash. gonna mess with it a little more tomorrow if i get some extra time
 

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#3 ·
Thanks big gear head! I moved my thinnest shim from right side of carrier to left and ended up with .003_.004 back lash, but the pattern was a little different I though I took a picture of that pattern but can't find it.
I think your right about taking a little out of the pinion and tightening back lash up. I will try that and report back.
Thanks again
 
#6 ·
Here's with .007 back lash. Only way I could get that back lash had to set up shims to where carrier had to be lightly tapped in. When I had .010 it would drop in pretty easy by hand. How's the pattern now. Didn't change too much
 

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#11 ·
Yes, the new bearing will probably change the depth a little. Be sure to check everything again after you change the bearing. You need to set the pinion bearing preload correctly each time you do a trial assembly so that your readings will be consistent. Your differential bearings should be tight enough that you can not pull the differential out by hand. You should put the shims in the left side along with the differential and then tap the shims in the right side.

I would run it like this if the pattern doesn't change with the new bearing. This pattern looks real good. What brand of gear is this?
 
#12 ·
There the cheaper richmond excel. And when shinning the carrier I put the shims in housing then dropped in carrier took some light tapping to get it seated.
I am afraid to damage the shims tapping in. Is the straight edge on the pattern at the root of the gear ok? All I have is the single stock shim on pinion not sure of the thickness my caliper is kind of jumpy.
How much bearing preload should I have?
Also should I install with old crush sleeve and new bearings to check pattern before setting preload with new sleeve?
 
#22 ·
Pattern looks very good.
Sometimes they rattle a little even when everything is normal, I think it has to do with speeding up and slowing down as you turn it.
I did a late model Mustang yesterday with a Ford gear, The best pattern looked odd due to how the gear is lapped, and it rattled a little which made me nervous, but it was noise free on the test drive
 
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