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Old 02-21-2014, 06:08 PM   #1
BigCountryx
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Factory posi install

I'm not opposed to a full rebuild but my 70 has a factory open carrier with 3.73. I've got a posi unit with 3.73 ring gear out of a 67 with all the bearings and shims. What's the chance that it'll drop in with minimal shimming required?
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1972 Pale Yella 2WD Blazer ..... 350HO/700R4.... '68 Clipped
1970 Original Paint SWB Farm Truck ..... 5.3/4L80.... 2x HRPT Participant
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Old 02-21-2014, 06:21 PM   #2
Kennuck
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Re: Factory posi install

If you can drop in both the ring and pinion from the posi unit, your chances would be better. No guarantee it will work but it should be close and easy to dial in by checking pattern on gear teeth.
As far as using your 70 pinion with the 67 ring gear this is not recommended as the ring and pinion wear in to each other over time.
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Old 02-21-2014, 06:56 PM   #3
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Re: Factory posi install

You beat me to it. Lol
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Old 02-21-2014, 07:19 PM   #4
BigCountryx
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Re: Factory posi install

What about bolting my 70 ring gear to the 67 posi carrier? This going to get me into a total re - setup more than likely?
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Old 02-21-2014, 07:22 PM   #5
Kennuck
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Re: Factory posi install

Yes bolting your 70 ring gear would be ok and might get you close. You will still have to check the tooth pattern. You might get lucky.
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1970 Short Wide
5.3 4L60E BlackBear tune
3:73 gears, Boyd's Tank
2.5 / 4 drop 5 lug disc brakes
Vintage Air
18x8 Ridlers 255/55 frt. 18x9.5 275/60 rear
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Old 02-21-2014, 07:26 PM   #6
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Re: Factory posi install

Here is a link to help you pattern the gears. Also don't forget to check backlash. http://www.sierragear.com/ring-and-pinion-gear-pattern/
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1970 Short Wide
5.3 4L60E BlackBear tune
3:73 gears, Boyd's Tank
2.5 / 4 drop 5 lug disc brakes
Vintage Air
18x8 Ridlers 255/55 frt. 18x9.5 275/60 rear
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Old 02-21-2014, 07:27 PM   #7
BigCountryx
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Re: Factory posi install

Hopefully it'll be in the ballpark and just need some tweaking. I've set up a couple before but it's an all day affair for me from scratch and I was just hoping to avoid that. Thanks guys.
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1972 Pale Yella 2WD Blazer ..... 350HO/700R4.... '68 Clipped
1970 Original Paint SWB Farm Truck ..... 5.3/4L80.... 2x HRPT Participant
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Old 02-21-2014, 09:11 PM   #8
Bigdav160
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Re: Factory posi install

You'll be fine with your old ring and pinion. Just set your backlash and add a couple thousandths extra on each side for some preload.
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Old 02-21-2014, 09:46 PM   #9
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Re: Factory posi install

Thanks
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Old 02-21-2014, 11:03 PM   #10
WIDESIDE72
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Re: Factory posi install

Years ago I bought a 8.5" rear axle for my 79 malibu. The axle came out of an early 80's 442. It was 3.73 open the p o had a posi but was scared to install it. It went in with minimal fuss. Btw the way i know the axle was in fact out of a 442 was only the 442 came with 3.73. Posi was optional. Buick GN had 3.42 posi. I understand the 8.5" rear behind the Buick 3.8 turbo, but why behind the 307 Olds but not behind the 305 in the Monte SS?
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