I got the vin number off of a 84 camaro my dad recently bought for parts. I know it is 84 z28 with the 150 hp 305. I also know it has the automatic tranny and the rearend gear ratio is 3.23. Is it a posi or not. I would just jack it up and check but we just got about a foot of snow so i cant check rite now.

 

You'll have to look for the RPO code G80 in the center console to know if it has a posi providing the diff is still original. Providing it is still original, the diff oil probably needs to be replaced. While the cover is off, look inside to see if it's a posi, gov lock or open diff.

 

my 89 RS doesn't have the codes sticker in the center console so how would i be able to tell what size differential i have, cause i am thinking that when i do my restoration of changeing it to something else but i want to make sure it will work first???

 

Size? Your 89 will have a 7.625" 10 bolt with 26 spline axles. The best way to know exactly what gears are in it and if it has a posi or not is to pull the cover off and have a look. A previous owner could have changed stuff.

7.625 (7-5/8) and 7.5 (7-1/2) are the same. The ring gear is just slightly larger but everything else is the same. Even though the ring gear was increased in size, it's still referred to as a 7.5" diff.

 

ok, thanks. and i know that mine is not a posi but rather a limited slip, i can tell that by the passengers tire spinning way before the drivers. But i am thinking about putting a Ford 9" posi rearend in it, unless there is a cheaper or better way to get a posi rearend in it, but i dont know if i have to do a lot of modifying yet to install the ford 9"

 

Posi and limited slip are the same thing. If you wanted a 9", you'd best buy an aftermarket bolt-in. There's no easy way to put a junkyard 9" in.

 

i wasnt going to get a junkyard rearend in, i can get it from my work, since i work at advance auto parts, but i thought there was a difference in posi and limited slip. I though the limited slip diff had one spider gear locked onto the ring gear and the second spider gear only kicked into th ring gear when the first spider gear has done so many rotations. Can you explain the different rearends???

 

Posi is a GM term for a limited slip differential. Ford's version is called Trac-lock. GM also used what's called a governor lock or Gov-loc. It's an open diff but when one wheel spins more than the other, locks grab a toothed gear to lock the diff. It isn't very strong and is easily broken. Typical posi's use clutches or cones but they can also fail since they are designed to wear out.

There are many other types of locking or posi type differentials. Detroit locker, Lock Right, Powertrax, Eaton and Auburn posi's. They all perform the same job but all do it a little differently. Limited slip means the diff will operate like a normal differential by allowing the outside wheel to turn faster than the inside wheel around corners. The limited slip differential will transfer power to the wheel with the most resistance to always provide the best traction.

I doubt Advance Autoparts will have a 9" bolt in diff for a third gen unless they supply aftermarket parts from Currie or Moser. You can't put 9" parts into your 10 bolt GM diff.

 

We do not sell a bolt in for my third gen, but there is a bolt in for an 89 mustang that is the 9" that most people use when useing a ford 9" posi, all i was doing was asking opinons on whether i should put a ford 9" posi (which i believe is a better differential) in my car or if there is a better way to get a better differential??

 

It'd be the same as putting a junkyard rear in. If it wasn't made specifically for a thirdgen (or a fourthgen), it isn't going to fit without more trouble than it's worth.

 

so what would you recomend me putting in there??