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What's a 'posi'?


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#1 willfxp

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Posted 31 August 2003 - 10:01 PM

I was talking to a guy online today and he said I should upgrade my "posi". What is it? Thanks.
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#2 MCourson

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Posted 31 August 2003 - 10:03 PM

Posi is a locker rear end where both wheels spin instead of one like in an open differential rear end. For GM it is RPO code G80.

Edited by MCourson, 31 August 2003 - 10:04 PM.

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#3 willfxp

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Posted 01 September 2003 - 12:30 AM

Posi is a locker rear end where both wheels spin instead of one like in an open differential rear end. For GM it is RPO code G80.

A locking differential? Not a limited-slip? Interesting term.. hehe... I wonder why he didn't just say 'locking diff'...

Thanks!
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#4 Butch 02 Denali

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Posted 01 September 2003 - 09:46 AM

Posi is a term that GM starting using in the 60's when they were promoting the muscle cars. It refers to any type of locker or limited slip. It became such a common term, like "Coke" is, that all the automakers and the aftermarket picked it up. Not used so much today, but you can tell someones age by their use of it!!!

I have a posi in my truck! :smash:

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#5 willfxp

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Posted 01 September 2003 - 11:25 AM

Posi is a term that GM starting using in the 60's when they were promoting the muscle cars. It refers to any type of locker or limited slip. It became such a common term, like "Coke" is, that all the automakers and the aftermarket picked it up. Not used so much today, but you can tell someones age by their use of it!!!

I have a posi in my truck! :(

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Ahh.. so it means "not an open diff" ? :smash:


Thanks,
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#6 Greg

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Posted 01 September 2003 - 06:36 PM

Posi is short for Positraction.

#7 willfxp

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Posted 01 September 2003 - 07:46 PM

Posi is short for Positraction.

:smash: Thanks. Makes sense now.
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#8 Shotgun

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Posted 01 September 2003 - 08:03 PM

GM rearends today are not a true positive traction,,they are limited slip or in other words a locking diff.In the old days with true positive traction rear ends when you would turn sharply you could hear it ratcheting as you turned because your inside wheel when turning was rolling less than the outside wheel.They were locked all the time ans there was a ratchet mechanism in the rear end or you wouldn't even be able to turn.I'm not a rear end expert but i tried to explain it...lol
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#9 chevy38fan

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Posted 01 September 2003 - 08:05 PM

close enough shotgun..

that's what they run in NASCAR, are the true positractions... or detroit lockers as some call em..
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#10 willfxp

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Posted 01 September 2003 - 08:09 PM

close enough shotgun..

that's what they run in NASCAR, are the true positractions... or detroit lockers as some call em..

I would have guessed NASCAR used open differentials because locking ones eat up more rubber and it wouldn't be common for one tire to lose traction.
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#11 robsawatsky

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Posted 01 September 2003 - 10:50 PM

For a description of the current G80 Eaton differential used in GM products see:

http://www.automotiv...ockingdiff.html

If you want to see what the difference is between a clutch type limited-slip and a locking diff see:

http://www.traction....oduct.htm#what2

#12 chevy38fan

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Posted 02 September 2003 - 07:16 AM

the reason they use the locking diff's is because of traction. they get a lot better traction with both rear tires driving the car, instead of just the right rear.
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