My BW 2.77 9 bolt went out a while back and I bought a rear off the classifieds here. It's a 10 bolt 3.73 with rear discs. MY brother has the car right now and he had some of the mechanics where he works help put it in (he's got mechanical aptitude, but he's not that smart when it comes to tech). Anyway, he swears up and down that the rear isn't POSI. The guy I bought it from said it was off an 85 IROC (sounded right to me), but I could swear all rear disc 3.73 rear ends were POSI....the numbers are rusted away...tried scrubbing and everything...they're gone.

KElly

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If you've gotta fix it, fix it better than stock.

 

you will need to open it up. then look inside the carrier hole if it is just 4 gears with no springs or lever stuff than it is just an open rear the posi rears have springs and or levers It is just that simple

 

hold one axle still,if you can turn the other axle its not a posi or its a posi that needs rebuilt

 

If it's from an '85 it could be an Eaton Locker (Guvlock) limited slip. A 3.73 limited slip would have the code "8PS" on the front of the right axle tube. An open 3.73 would be "8JB" or "8KD". These Eatons act like an open diff when up on jack stands, until you spin one wheel at about 100 rpm or more and then the clutches engage and the other wheel stops spinning backwards.

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1985 Yellow IROC-Z 5.0 HO, T-5 3.73 Torsen, 4 wheel disks
PFCM pads, GTA wheels, Koni yellows, B&M Ripper, Dynomax

 

like I said open and check thats the only proven way

 

If it's posi, it's probably worn out anyway.


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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

 

yep the only sure way is to pull the cover and take a look. doesn't hurt to do a little inspection and change the lube and additive.

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ICON Motorsports

1st & 3rd
MM Black Diamond 538 F&AM