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popballz
Member
Joined: 18 Nov 2007
Posts: 533
Location: Tacoma, WA
1989 Pontiac Firebird
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 Posted: Sat Aug 22, 2009 12:50 pm Post subject: posi or not? |
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do i got a posi?
that is the question.
i got a 1987 firebird trans am, 305 v8 tpi, stock i think.
i did a little burn out and there was two lines but they were both pretty light (i don't wanna waste my fairly new tires)
when its off the ground, and i spin one, they both turn in the same direction, but i can move the passengers side and have the drivers side stay still.?
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popballz
Member
Joined: 18 Nov 2007
Posts: 533
Location: Tacoma, WA
1989 Pontiac Firebird
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| Posted: Sun Aug 23, 2009 3:28 pm Post subject: |
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ok, does this pic help?
there is two lines there....?
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Quasi-Traction
"I have petals"
Joined: 24 Oct 2005
Posts: 3873
Location: stumptown
1986 Chevrolet Camaro Berlinetta
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| Posted: Sun Aug 23, 2009 5:30 pm Post subject: |
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sometimes with a sudden drivetrain shock, (like dumping the clutch) you can get the spider gears to shock and move in sync with the ring gear. usually it only happens for a second or two, but there's freak incidences where it can go on for longer.
well...at least that's the way I've understood it...perhaps someone can correct this if its untrue?
that being said, I'd check your RPO codes and see if you have the G80 code on the build sheet. if you don't, its pretty safe to say you have an open diff.
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aaron_sK
Member
Joined: 23 Jan 2006
Posts: 8834
Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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| Posted: Sun Aug 23, 2009 5:59 pm Post subject: |
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Even if he did have a limited from the factory, theres no guarantee that it's still in there, or that it works.
Doing a donut is not a good indicator of your rearend. Your tires are spinning because the suspension is being loaded and unloaded from side to side. Brakestand it just for a bit and see what happens. |
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Dewey316
The Lama
Joined: 08 Jan 2004
Posts: 7295
Location: Bringing the tech
1990 Chevrolet Camaro RS
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| Posted: Sun Aug 23, 2009 6:16 pm Post subject: |
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| aaron_sK wrote: | | Brakestand it just for a bit and see what happens. |
That doesn't even work, if you have equal traction loss, both wheels will spin.
Both tires turning the same direction is a good indication that it is a posi. But, the ONLY way to tell for sure, is to just pull the rear cover, and look. |
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aaron_sK
Member
Joined: 23 Jan 2006
Posts: 8834
Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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| Posted: Sun Aug 23, 2009 7:18 pm Post subject: |
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| Dewey316 wrote: | | the ONLY way to tell for sure, is to just pull the rear cover, and look. |
This is true. However for the cost of fluid and expenditure of time, I have found a straight-line mild brakestand to be a fairly accurate and mildly entertaining indicator.  |
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Twilightoptics
Hardcore (12sec Club)
Joined: 13 Jan 2004
Posts: 9191
Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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| Posted: Sun Aug 23, 2009 8:10 pm Post subject: |
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Jack the car up on the pumpkin, in Neutral, turn one wheel. If the other spins in the same direction it's a posi. If it doesn't spin, or it spins in the opposite direction is an open or a worn out posi.
Those look like Posi marks to me.
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91camaro_rs
Member
Joined: 03 Dec 2008
Posts: 1712
Location: Fox Island, Wa
1991 Chevrolet Camaro RS
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chevymad
Master B
Joined: 11 Jan 2004
Posts: 5476
1987 Pontiac Formula
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| Posted: Sun Aug 23, 2009 9:45 pm Post subject: |
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| Twilightoptics wrote: | Jack the car up on the pumpkin, in Neutral, turn one wheel. If the other spins in the same direction it's a posi. If it doesn't spin, or it spins in the opposite direction is an open or a worn out posi.
Those look like Posi marks to me. |
Unless its a Zexel/torsen!  Always an exception to the rule. My torsen acts completely like an open diff when the rear end is jacked up.
Of course unless he has a 4th gen rear, its not likely he has a zexel either. |
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popballz
Member
Joined: 18 Nov 2007
Posts: 533
Location: Tacoma, WA
1989 Pontiac Firebird
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| Posted: Sun Aug 23, 2009 9:59 pm Post subject: |
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| Twilightoptics wrote: | Jack the car up on the pumpkin, in Neutral, turn one wheel. If the other spins in the same direction it's a posi. If it doesn't spin, or it spins in the opposite direction is an open or a worn out posi.
Those look like Posi marks to me. |
they spin in the same direction, but i was able to spin the passengers side with the drivers side staying still....
worn out posi seems like it could be a match!
and i could not find my RPO list, 
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