8.75 Posi Carrier in 8.875 Full Size

MikeMike123
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8.75 Posi Carrier in 8.875 Full Size

Postby MikeMike123 » Tue Jul 03, 2012 2:26 pm

First I want to say that I am new to this site, and the information is great. I have a 69 Catalina with 2.73 open rear (10bolt/12bolt Full Size rear). I also have a corporate 8.75 posi rear with 2.73 gears. Since both have 8.875 ring gear diameters will the posi carrier fit into the Catalina rear.

Thanks,

Mike

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monzaz
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Re: 8.75 Posi Carrier in 8.875 Full Size

Postby monzaz » Tue Jul 03, 2012 9:59 pm

Well most likely the 8.75 posi unit will have 28 spline which will not work in the 1965-1970 Pontiac rears which are 31 spline.

The 8.75 units are derived from the early units but turned into 28 spline c-clip low horse units. Even the castings got smaller BUT the spiders did get improved.

So check your axle spline count- then if they are both 31 spline give it a shot and see if the ring gear bolts up. cross them fingers. :) Jim
J D Race

MikeMike123
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Joined: Tue Jul 03, 2012 12:46 pm

Re: 8.75 Posi Carrier in 8.875 Full Size

Postby MikeMike123 » Wed Jul 04, 2012 5:57 am

Jim,

Thanks for the quick reply. It turns out but my 8.875 and 8.75 have 31 spline axles. Guess I got lucky on that one. The 8.75 does have C-clips vs the 8.875 has the end plates.

I do have a follow up question. Both units have "41 15" gears. (2.73 ratio). I assume I want to keep mating gear and pinion together. Is it better to keep the ring gear on the posi unit and swap pinion gears also (move the entire guts from the 8.75 rear to the 8.875 rear), or should I just swap carriers and keep the original gear set in place (only move the posi unit from the 8.75 to the 8.875 rear), or does it not make a difference either way. Hope this question makes sense.

Thanks again,

Mike

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monzaz
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Re: 8.75 Posi Carrier in 8.875 Full Size

Postby monzaz » Fri Jul 06, 2012 7:35 am

ALWAYS always keep he ring and pinion together. So you will need to remove the 2.73 from the posi and install the other 2.73 ring that matches the older era rear pinion. NEVER mismatch gears even with the same ratio. '

I am sure it could be done BUT you might get noise etc. If it were the only way and we lived in a MAD MAX world. You would just do it...LOL. :D Jim
J D Race


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