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Old 11-29-2003, 08:23 PM
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chevy rearend

i have a 85 chevy truck im rebuilding when i got it , it didnt run so i was wondering how would i find out if its positract. its a 10 bolt 8 1/2 inch thats all i could find out. if it isnt could i shim it up to make it almost full time posi tract

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Old 11-30-2003, 08:05 PM
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No you cannot shim it up (whatever that means) to make it a posi trac. Jack up the rear so both tires are off the ground. Rotate one wheel, and if the other wheel rotates the same way it is a posi trac. If it rotates the opposite way from the wheel you are rotating, it is not a posi trac.

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Old 12-01-2003, 09:56 AM
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Junk Yard Dog

I am beginning to sound like a junk yard dog. No Shimming is correct. After you check for POSI and find out that it isn't, call the local junk yard and ask how much for a REBUILT PUMPKIN WITH POSI. The pumpkin is affectionitly the gear section of the rearend. I just purchased a rebuilt rearend for my 55 P.U. and had it built with posi. Cost $600. Mine was the whole rearend, so your PUMPKIN should be about half.

Good luck.

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Old 12-01-2003, 05:41 PM
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Most likely the truck does not have a locker or limited slip or posi or whatever you want to call it.
Most 73-87 chevy trucks were not sold with a locking diff, even though it was available.
Most websites that cater to this series trucks' history don't include much about any sort of locker, but the most popularly mentioned from the factory is the GOV-LOCK or the [color=red]exploding[/color] locker, for the simple reason that it used centrifugal force to engage the locking function = too many RPM's when engaged turns it into a suicidal locker.
Other than that it worked as advertised though.
To find out if it has one though- block the front wheels, put the transmission into neutral, jack up ONE side of the rear and turn the wheel.
If it turns you don't have one (some GOV-LOCKs will turn though).
The most positive way to tell is to remove the cover and change the lube as no-one ever does this even though it is included in the regular maintenance, and just simply change the fluid, or as long as you are in there remove the axleshafts and change the questionably OLD axleshaft seals and bearings.
All you would really have invested in this venture is less than $50 bucks and many more years you can neglect the axle like it has been before you got it.
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Old 12-01-2003, 10:48 PM
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I'm not sure what thom meant by telling you to get a new pumkin as the chev 10 bolt 8.5" does not have a removable center section. M&M has the right idea, remove the cover and look in the carrier. If it is a posi chances are that its worn out anyway. Either way I would seriously consider ordering a new eatons posi after market carrier it is much stronger than the original and isn't the gov-loc design (which tends to grenade). I'm not sure I understand what you meant by "shimming it" unless you are referring to welding the spider gears together basically making a spool which I wouldn't recommend for street use.
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Old 12-02-2003, 05:59 PM
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by shimming i meant i hear d that you can shim it up with washers to make it posi tract thank for the help i lifted up today and found out when i rotate one wheel the other is oppopsite rotation thanks for the help
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