I was thinking of looking around in the local junkyards for a posi rear and was wondering how I could tell if a rear is a posi or not. I know if it was a solid posi both tires would spin when you turned one but I don't know how to tell if a rear is a limited slip rear or an open rear.

Little help please?

 

it has a tag hanging off the differential case if its posi, no tag no posi

 

Well thanks, thats simple enough. Any idea what the tag says? Does it just say 'posi' or something like that? Is there any chance the tag could fall off?

 

a posi(limited slip) will make both axels turn the same way a open will spin the axels in oppsite directions. a solid posi or spool is very unlikely for a 10 bolt in a junk yard. s10 carriers are the same for a 10 bolt but watch the number of axel splines

 

I wouldn't count on a tag being there. Gotta pull the cover off and take a look.

You can also go by the RPO code if the car still has the sheet. Example, GT4 is a posi/3.73/disk rear. But, someone might have swapped the axle, so you should still pull the cover to check. Also make sure there's no funny pieces of metal stuck to the diff cover's magnet!!

82-84 Trans Am's and Z28's with a 5 speed, and engine code "G", have a 3.73/posi/disc- same axle I put under my car. But the posi's really an Eaton GovLock piece o crap.

'85 was the last year of f-body for a 3.73 gearset... but it wasn't in a posi- it was a 3.73/open/drum axle, found under a "Camaro H.O.". The words "Camaro H.O." are found on the rear driver's side of the Camaro's bumper- and if you find one of those cars in the junkyard (rare), I bet the axle's gone!

Like Massey said, S10 blazers might also have the GT4 code; you could pull the posi and gearset from one of those. Their axleshafts, I believe, are slightly longer than ours- and the axle housing is meant for leaf springs, so the posi & gearset is all you can grab. That's why ya gotta make sure of the axle spline count, to make sure your car's axles will slide in. 82-88 f-bodies are 26 spline, 90-92 f-bodies are 28 spline, and the "changeover year" of 1989 f-bodies can have either 26 or 28 spline axleshafts.

Finally you can ALSO tell by picking up a Haynes 82-82 Firebird or 82-92 Camaro manual. In the book, in both the "rear axle" section and the last chapter "updates for 85-92", Haynes lists the common axle codes. The number is stamped into the passengerside axle tube, and faces "forward" towards the front of the car. You'll need a wire brush to scrape the crud off. I've also found that it helps greatly to wet your finger and rub it over the numbers to make them stand out the best.

It's a pain (crawling for axles), that's for sure.

Tip; if you do find an axle and want to pull the cover to check it, take a blade knife to an empty antifreeze jug. Cut out the side. This makes a junkyard drain-pain for ya that'll hold a gallon; enough to empty the rear axle into. The junkyard should have a metal "oil only" disposal tank that you can empty the antifreeze bottle into; just remove the cap and pour it in, nice and mess-free.

And you should really pull the cover anyway before you buy an axle!! The junkyard won't argue, either- but they'll insist you don't let the gear oil spill all over the ground.

Honestly, best bet is to save $$ for a new posi. Otherwise you might wind up with that piece o crap gov-lock that I got; which blew up after 6 months. Now I'm back on a non-posi axle. You also might wind up with a posi whose cones are burnt out, and it'll act like an open rear.

 

The only way to tell, is to pull the cover and do a visual check.

 

What would I be looking for if I puled the cover off??

 

you need to find the numbers stamped in the gears they tell you what raito they are. would be somthing like 10:37 for example therefore being 3.70 gear ratio..if you cant find that count the teeth on both gears.

 

As far as a posi or locker, you'd want to look for what yours doesn't look like. That's the best answer I can give, sorry! Maybe someone in the <a href="https://www.thirdgen.org/techbb2/forumdisplay.php?s=&forumid=19" target="newwin">trans/drivetrain forum</a> has a picture; you could ask there.

 

Um, ok, sounds good, Ill have to pull my cover then. Thanks guys

 

If nothin' else, it's a good excuse to change the gear oil. You can either use a gasket & gasket sealant when you reinstall the cover, or, just lay down a bead of ultra copper rtv.

And for anyone who hasn't worked with gear oil; be prepared, the stuff stinks like cat ****! (gag)

When I refill my axle (thru the plug on the top passenger side of the diff case, use a 3/8th ratchet without a socket to remove the plug), I stick an old piece of fuel line onto the end of one of the plastic bottles of 80w90 gear oil. No mess! (Then I re-wrap the piece of fuel line in a paper towel and stick it in a zip-lock bag so it doesn't stink up the damn place)