alright i looked all over the web for specs on the stock rear that a 1983z has and could not find it anywhere. maybe i wasnt looking hard enough i dont know. but i would like to make my car have a posi rear how is the best way about going to do this? i was looking at the powertrax no slip traction system on jegs but i couldnt figure out what the specs are. if some one can help me out that would be great. thanks.

 

What exactly are you looking for? Differental model, spline count, gears, install and rebuild kits??

 

If you just want a posi, then get a complete rear end from a salvage yard that already has a series3 posi carrier. that should cost a lot less than an aftermarket posi unit. Plus you will avoid the process of setting up the diff.

 

plus, an 89 or later rear would be 28 spline axles instead of the 26 spline used in the earlier models. - Stay away from the powertrax or other locker type units for a street car with c-clip axles. The end results of using these can be catastrophic.

 

ok so when i go to the junk yard how can i tell whats what?

 

Factory posi rears have a metal tag under a cover bolt. But, those tags don't always get put back on when the rear is serviced, so that's only a start.

With one wheel held, you shouldn't be able to turn the other wheel. That's the 2nd best way to tell if it's a posi unit.

You should pull the cover and inspect whatever rear you are considering. That's Method #1 for determining what's in there. You'll either see 4 gears inside the carrier, or springs & plates. If 4 gears, put the cover back on and move to the next one. If springs & plates, look for the numbers stamped on the ring and pinion gears - dividing the larger by the smaller will tell you the gear ratio. 3.23 and above are 3-series carriers (if stock).

There is also a code stamped on top of the passenger side axle tube. If you take the book with you, you can tell what was originally installed in that rear (year, posi or open, gear ratio).

As stated, '89-later are the best ones to go for.
----------
Been draggin' and drivin' one for years. No catastrophe to date.

 

alright awesome thanks for everyones help!

 

I own a 83. It came with the 3 speed auto and i put a 400 HP 350 in it and the stock rearend had limited slip , 2.73 gears, 10 bolt, 7 1-2 ring gear. I found a posi trac from summit racing for 89$! An new axle seals were 5$ and 80-90w gear oil, an back on the road the next day, ripping tires up like butter, an i run 295-50-15's on the rear. With the HP I can turn them big meats,but if I had the 190hp 305 it wouldn't go like it should- id have to re gear it to 3.73 or 4.11 like I did when I first got it an it made that 305 feel snotty as f!!. But when the 350 was built, an ready to go in, it was under-geared, so I sold my stock limited slip diff with the 4.11s, an bought a stock one from a friend that came out of a 86 z28, has the factory 2.73 gears to go with the 3 speed. Now with the locker, I can't corner like I use to,(well I can I just have to saw at the wheel alto more) but it launches straight, an runs in the low 12's @ 138 mph. Plenty for me, an its still streetable.

 

Factory in my 83 sport hardtop. A 10 bolt 7.5 ring gear, 2.73 limited slip gear ratio, 26 spline axles.

 

Did you notice that this thread is 9 years old?

What you bought is a mini spool, not a "posi", and not a good idea for street use. They are dangerous!