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Can anyone explain how a posi unit works?

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Old Feb 12, 2001 | 03:17 AM
  #1  
Dan87IROC-Z's Avatar
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From: Fort Collins, Colorado
Can anyone explain how a posi unit works?

Can anyone explain how a posi unit works? I am totally clueless as to how they eliminate wheel spin.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
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Old Feb 12, 2001 | 06:06 AM
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buddman91rs's Avatar
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From: Niceville, Fl USA
with an open diff. if you get one wheel off the ground that one will spin(bad for towing)
so thats why 4x4's use locking diff. also with a open diff. all your power is to your right rear wheel so thats the one that spins all the time when you floor it(unless it's stuck then the other one spins) with a locking diff. acts like an open diff. in corners but is a straight axle on straight aways. i like to think of it as a clutch, as you go into a corner the diff. unlocks and slides open so that the inside and outside wheels can go at different speeds and you can go throught the corner w/o peeling out. as you progress back out of the turn the diff. slides closed and is a straight axle again so you have more traction. when they say limited slip they mean that it is limiting the slip to the right rear and transfering power to your left rear or vice versa. if anyone else could help on this explanation i would appreciate it. it would be a hellufalot easier to show you instead of trying to explain it in writing. hope it helps man

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1991 RS LO3
mods: 14" chrome air cleaner, straight-piped after cat exhaust with one chrome dual tip on the left side.
future mods: headers, removing smog equipment, and as many cheap mods as i can find
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Old Feb 12, 2001 | 12:07 PM
  #3  
Christos's Avatar
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From: Littleton, CO
Car: 1986 Iroc Camaro
Engine: 305 TPI
Transmission: Th700R4 Jr. Raptor
http://www.howstuffworks.com

there is an article there about diffrentials, and what they do, and hwo they work. also more articles on car goodies.

<a href="http://www.howstuffworks.com">How Stuff Works</a>
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Old Feb 12, 2001 | 01:10 PM
  #4  
RB83L69's Avatar
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From: Loveland, OH, US
Car: 4
Engine: 6
Transmission: 5
A posi unit is basically just a set of clutches that connects the 2 axles together. In order for the axles to turn at different speeds, such as they have to do when going around a corner, there has to be some minimum amount of torque difference available to force the clutches to slip. This helps straight-line traction by keeping one wheel from spinning uncontrollably whie the other wheel just sits there with no torque on it at all.

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"So many Mustangs, so little time..."
ICON Motorsports
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Old Feb 12, 2001 | 01:27 PM
  #5  
Godti's Avatar
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From: Edmonton Alberta
Car: Trans AM
Engine: 305 TBI
Transmission: 5spd
If ya got time read this:

http://www.howstuffworks.com/differential5.htm

Now, after I read this article Im even more confused. I was told that limited slip is GM's version of Posi. If thats the case why do I always get the one-wheeler peeler.
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Old Feb 12, 2001 | 03:24 PM
  #6  
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<font face="Verdana, Arial" size="2">Originally posted by Godti:
Now, after I read this article Im even more confused. I was told that limited slip is GM's version of Posi. If thats the case why do I always get the one-wheeler peeler.</font>
Possibilities
1. You dont have posi.
2. Your posi is worn out (clutches or springs)
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Old Feb 12, 2001 | 03:27 PM
  #7  
CanadianBeast's Avatar
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From: The Great White North
Go to The Best Damn Garage on the Internet, and read what he has to say. That should help.
Sorry I forgot the adress but there is a link from my page.

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89 Iroc-Z
L98, cat_back, no cat, K&N, 3.42 gears, airfoil, shift kit, accel everything, B&M megashifter, useless JET II chip
Coming SLP headers, pulleys, afpr, drag radials
www.oramac.cz28.com
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