63 Impala wagon rear end, lots of dumb questions! - Impala Tech
Transmission & Driveline Transmissions & Differentials

 
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post #1 of 5 (permalink) Old 02-20-2013, 07:30 PM Thread Starter
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63 Impala wagon rear end, lots of dumb questions!

I have a 3.08 open rear, want to upgrade to posi. can I pick up a used posi pumpkin on ebay or whatever and install the posi in my non posi pumpkin? also, I see i can buy out of say, summit or jegs, a posi unit. will this bolt into a non posi pumpkin or will I have to find a posi pumpkin to put the new parts in? If I stay with a factory posi I pick up whereever, are parts still widely available for rebuilding the old posi unit?
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post #2 of 5 (permalink) Old 02-21-2013, 07:07 AM
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Quote:
Originally Posted by Nodak View Post
I have a 3.08 open rear, want to upgrade to posi. can I pick up a used posi pumpkin on ebay or whatever and install the posi in my non posi pumpkin? also, I see i can buy out of say, summit or jegs, a posi unit. will this bolt into a non posi pumpkin or will I have to find a posi pumpkin to put the new parts in? If I stay with a factory posi I pick up whereever, are parts still widely available for rebuilding the old posi unit?
can I pick up a used posi pumpkin on ebay or whatever and install the posi in my non posi pumpkin?

Maybe. They are offered from time to time but because they are so rare and highly prized by 1953-'62 Corvette owners the price for a factory "P" case runs from $1,500 to $2,300 to successfully bid on one. If you buy one yes you just bolt it in and go.

also, I see i can buy out of say, summit or jegs, a posi unit.

Provided the parts that they are selling are for your rear end, and not a 1965-'72 rear end which also had an 8.2 inch ten bolt but used entirely different parts.

will this bolt into a non posi pumpkin or will I have to find a posi pumpkin to put the new parts in?

Once again this depends upon fitting your rear end. You have a Salisbury drop out rear end as opposed to the same size Spicer rear end where the gears stay in the case and you access them through a an inspection plate in the rear of the case. The aftermarket makes parts for Spicer rear ends that work inside an open differential case to convert it into a limited slip or posi. They generally use gears instead of clutches due to the lack of space but work as well.

If I stay with a factory posi I pick up whereever, are parts still widely available for rebuilding the old posi unit?

No. They were not widely available when these cars where new as there where no posi's sold to enhance performance. People back in the early sixties, if they ordered a posi, bought it to survive driving in winter snows. So only a traveling salesman would order that option normally. Since there are very few traveling salesman cars surviving today (they were usually driven into the ground, and then scrapped), there are very few posi cases surviving. The posi case is different from an open case. It has a "P" cast into the drivers side of the case to identify it.

Another option is a Pontiac-Olds rear end which was sold as a high performance rear and had a lot more posi units sold for it than Chevy had. The Olds/Pontiac rear end is uncommon today because racers used them up in the late sixties as they were extremely strong and rarely broke unless you where trying to pump 2,000 horsepower through it spinning slicks for a full quarter mile.

Big Dave
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post #3 of 5 (permalink) Old 02-22-2013, 10:41 PM
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Quote:
Originally Posted by Nodak View Post
I have a 3.08 open rear, want to upgrade to posi. can I pick up a used posi pumpkin on ebay or whatever and install the posi in my non posi pumpkin? also, I see i can buy out of say, summit or jegs, a posi unit. will this bolt into a non posi pumpkin or will I have to find a posi pumpkin to put the new parts in? If I stay with a factory posi I pick up whereever, are parts still widely available for rebuilding the old posi unit?


Here is some info:
http://www.chevytalk.org/fusionbb/sh...hp?tid/223912/
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post #4 of 5 (permalink) Old 02-23-2013, 08:23 AM
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I have a buddy that has one sitting in his garage for years. I may have to go check on it.
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post #5 of 5 (permalink) Old 02-23-2013, 10:43 AM
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On a cautionary note, let me state that there is a reason there are very few PosiTraction units available. The 8.2 inch ten bolt was designed before Chevy even thought of going to V-8 power (Chevy was the last division to acquire a V-8 in 1955 and it was designed as an improved upgrade to the successfully 331 cubic inch Cadillac engine only a bit smaller in size). The reason Chevrolet stopped making their own rear ends and bought an off the shelf rear end from an outside vendor (Dana's Spicer Division) was because theirs were incredibly weak and was breaking under warranty.

I used to break one a week, or on demand if showing off. I carried not one, but two complete rear ends around with me in the trunk of my '53 Chevy because my ultimate 409 power plant would break either the Borg-Warner T-10 or the rear end at the dropping of an arm, or flash light.

A posi helps by distributing the load evenly to both axles, but even with a posi installed it was usually the spider gears that broke in the rear end (and yes I used to own three "P" case rear ends at oner time). I finally went with an Olds rear end to stop breaking them. Then I was able to concentrate on breaking T-10 transmissions every other week.

Back then parts were a whole lot cheaper, but I still had to solicit my friendship in the bone yards to find posi cases; usually having them shipped in by truck from across the country (two out of three came from North of the Mason-Dixon line).

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