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Old 04-02-2009, 04:25 PM
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How Do I Tell If Its Posi Trac

So Im Looking For A Posi Rear Out Of 67-79 Camaro Im In The Junk Yard. I Looked At 75 76 78 Camaros. I Jack Up A Few Cars And I Turn The Drums, One Side Turns One Way The Other Side Turns The Other Way. I Encountered A 72 Camero Where I Turned The Drum One Way, The Other Side Turned The Same Way, Is This Posi Traction? I Don't Want To Take The Differential Covers Off These Axles To Look. How Do I Tell? Any Help Would Be Appreciated.

Thanks Guys!

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Old 04-02-2009, 05:11 PM
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true posi will turn same way both wheels together, or the tire with the most traction will get power, not the one with the least traction
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Old 04-02-2009, 05:56 PM
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posi

Quote:
Originally Posted by fast68
true posi will turn same way both wheels together, or the tire with the most traction will get power, not the one with the least traction
sweet thanx
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Old 04-02-2009, 06:48 PM
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Ok lets define the types of rear ends that you will encounter from the year cars that you are looking at.
1: You have the open carrier one wheel drive non posi rear end.
2: The limited slip rear end. This one uses clutch packs and will slip some if to much traction difference occurs between the two drive wheels.
3: Locking deferential. Most of these use clutches in conjunction with a locking device that locks both wheels into full lock when a set RPM is achieved.

I have always used this method to check.

With the rear axle jacked up and off the ground (be sure to properly support the weight of the car, preferably on jack stands) the transmission in park or in gear (if it is a standard shift) and the parking brake off, rotate one wheel, if the wheel turns free and the other wheel turns in the opposite direction it is a plane old open carrier one wheel drive rear end. These rear ends can fool you so if the trans is in neutral or the drive shaft is out of the car have a friend grab the other wheel. If the wheel rotates freely with no drag while the friend is holding the opposite wheel, move on to the next car.

If the wheel can't be rotated or is real hard to rotate and the other wheel still tries to turn in the opposite direction but hard to rotate, it could be a limited slip or locking rear end. You can't tell if it is a locking differential or a limited slip until you pull the cover off the rear. If you find one of these check it some more by doing this.

Put the transmission in neutral and then rotate the wheel again. If the other wheel rotates in the same direction have a friend grab the other wheel and try to rotate it in the opposite direction or simply stop it from rotating. If it is hard to stop the other wheel or rotate it in the opposite direction it could be what you are looking for. The clutches on the limited slip and the locking differential can become worn to where it acts like the single wheel drive rear end. If the clutches are in good shape and with the car in neutral you will find that the other wheel rotates in the same direction and you can not hold it. These clutches are set to brake free at about 600 foot pounds of torque. Unless you are Godzilla you wil not be able to stop the other wheel from rotating. So after doing this little test to several cars take the cover off the back of the rear end to the one that you suspect to be what you are looking for and check for sure. I would hate to buy one that I thought was a limited slip or locking rearend only to get it home and find out that the reason it acted like what I was looking for is because the spiders were all gummed up or full of rust.

On GM cars from that era sometimes you can get lucky and find the option sheet still in the glove box. Sometimes it will tell you if it is a limited slip or locking differential.

Just a note: For all around street use I like the non locking limited slip rearends of that era made by Eaton for GM. On the locking differential I have had the locking mechanism come apart from to much torque and trash the rearend. With the limited slip clutch only type, it will give a little before it explodes.

Hope this helps!
Chris
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Old 04-02-2009, 07:00 PM
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Junkyard tip- All the 2nd. gen. T/A's had posi's as standard equipment. The downside is they had real tall gears in them- some way down in the 2's.
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Old 04-02-2009, 07:28 PM
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Quote:
Originally Posted by Chris Kemp
Ok lets define the types of rear ends that you will encounter from the year cars that you are looking at.
1: You have the open carrier one wheel drive non posi rear end.
2: The limited slip rear end. This one uses clutch packs and will slip some if to much traction difference occurs between the two drive wheels.
3: Locking deferential. Most of these use clutches in conjunction with a locking device that locks both wheels into full lock when a set RPM is achieved.

I have always used this method to check.

With the rear axle jacked up and off the ground (be sure to properly support the weight of the car, preferably on jack stands) the transmission in park or in gear (if it is a standard shift) and the parking brake off, rotate one wheel, if the wheel turns free and the other wheel turns in the opposite direction it is a plane old open carrier one wheel drive rear end. These rear ends can fool you so if the trans is in neutral or the drive shaft is out of the car have a friend grab the other wheel. If the wheel rotates freely with no drag while the friend is holding the opposite wheel, move on to the next car.

If the wheel can't be rotated or is real hard to rotate and the other wheel still tries to turn in the opposite direction but hard to rotate, it could be a limited slip or locking rear end. You can't tell if it is a locking differential or a limited slip until you pull the cover off the rear. If you find one of these check it some more by doing this.

Put the transmission in neutral and then rotate the wheel again. If the other wheel rotates in the same direction have a friend grab the other wheel and try to rotate it in the opposite direction or simply stop it from rotating. If it is hard to stop the other wheel or rotate it in the opposite direction it could be what you are looking for. The clutches on the limited slip and the locking differential can become worn to where it acts like the single wheel drive rear end. If the clutches are in good shape and with the car in neutral you will find that the other wheel rotates in the same direction and you can not hold it. These clutches are set to brake free at about 600 foot pounds of torque. Unless you are Godzilla you wil not be able to stop the other wheel from rotating. So after doing this little test to several cars take the cover off the back of the rear end to the one that you suspect to be what you are looking for and check for sure. I would hate to buy one that I thought was a limited slip or locking rearend only to get it home and find out that the reason it acted like what I was looking for is because the spiders were all gummed up or full of rust.

On GM cars from that era sometimes you can get lucky and find the option sheet still in the glove box. Sometimes it will tell you if it is a limited slip or locking differential.

Just a note: For all around street use I like the non locking limited slip rearends of that era made by Eaton for GM. On the locking differential I have had the locking mechanism come apart from to much torque and trash the rearend. With the limited slip clutch only type, it will give a little before it explodes.

Hope this helps!
Chris
if i do find the one that turns in the same direction and have a friend hold it but it still goes i take the cover off what am i looking for??
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Old 04-02-2009, 08:31 PM
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Quote:
Originally Posted by chevy bb 572
if i do find the one that turns in the same direction and have a friend hold it but it still goes i take the cover off what am i looking for??
You will be looking for clutches (or discs) up inside of the carrier between the axle gear that is inside the carrier and the carrier. They will look like shims on the wheel side of the axle gear. Depending on which type you have found, you should also be able to see a spring pack in between the left and right side axle gears. All of this is impossible to see if it has a closed carrier. On the locking differential type you will be able to see the locking mechanism. The picture is of a cut away view of a closed carrier unit. Most of the ones that you will find will be an open carrier meaning that they have a two to three inch access hole on one side or both sides of the carrier. Rotate the axle until the hole comes into view and look up in the carrier. If it is a limited slip you will be able to see the clutches or discs on the wheel side of the axle gears. Similar to what is shown in the picture. Note the discs on each side of the axle gears.
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Last edited by Chris Kemp; 04-02-2009 at 08:41 PM.
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Old 04-03-2009, 06:32 AM
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Quote:
Originally Posted by Chris Kemp
You will be looking for clutches (or discs) up inside of the carrier between the axle gear that is inside the carrier and the carrier. They will look like shims on the wheel side of the axle gear. Depending on which type you have found, you should also be able to see a spring pack in between the left and right side axle gears. All of this is impossible to see if it has a closed carrier. On the locking differential type you will be able to see the locking mechanism. The picture is of a cut away view of a closed carrier unit. Most of the ones that you will find will be an open carrier meaning that they have a two to three inch access hole on one side or both sides of the carrier. Rotate the axle until the hole comes into view and look up in the carrier. If it is a limited slip you will be able to see the clutches or discs on the wheel side of the axle gears. Similar to what is shown in the picture. Note the discs on each side of the axle gears.
ill keep you posted you have been great help i might just take some picks
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Old 04-03-2009, 08:53 AM
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one good burn out will tell ya ....
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Old 04-03-2009, 09:10 AM
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Quote:
Originally Posted by pepi
one good burn out will tell ya ....

ID LIKE TO BUY A REAREND AND PUT IT IN BUT DONT WANT TO BUY AND NOT HAVE IT BE POSI.
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Old 04-03-2009, 04:45 PM
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Quote:
Originally Posted by pepi
one good burn out will tell ya ....
I really love this test method! LOL
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Old 04-03-2009, 04:57 PM
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Posi



Open



The ID tag may also tell you.
Shane
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Old 04-03-2009, 05:44 PM
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I swear those graffiti guys are really getting good with their rattle cans. Those picks look just like burn outs. LOL just joking!
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Old 04-03-2009, 06:41 PM
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Originally Posted by Chevrolet4x4s
Posi



Open



The ID tag may also tell you.
Shane

Those black mark's need to be a wider!
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Old 04-03-2009, 07:15 PM
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Quote:
Originally Posted by prostreet6t9
Those black mark's need to be a wider!
YOUR MISSING THE POINT I KNOW WHAT POSI IS I WANT TO BUY A REAR END FROM A JUNKYARD KNOW ITS A POSI "BEFORE"I BUY AND PUT IN!
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