ok so im young and dumb and have a question. i have a 87 iroc stock 10 bolt with 273 gears and a limited slip/posi unit. i found someone with a slightly used set of 373s and is a series 3 carrier. would i be able to use it even tho mines a 273 wich a 2 series. or will i have to find 2 series 373s? looking to upgrade gear wise by spring

Assuming it came out of the same type of axle(10 bolt rear from a thirdgen, fourthgen or S10/S15) then yes you can use it. You will need both the gears and the carrier. If the carrier is not a posi unit you will lose that feature.

Your '87 will have 26 spline axles. In '90 the 7.5 rear end was upgraded to 28 spline axles. If these are both 26 spline then you could use them in your rear end. If the differential with the 3.73 gears is not a posi then you might want to just get a set of thee thick 3.73 gears and use the posi that you already have. Either way you go you are going to have to set up the gears. This will require setting the pinion depth, bearing preload and backlash so that the contact pattern is correct.

If your not experienced in setting up gears (and not everyone is, including myself) it may be easier to find a whole 3.42 gear LSD rear out of a newer 6 speed car, that way you could just bolt the whole thing in and not mess with it. Just some food for thought

so i will need him to send the carrier too and figure out wut year of car it came out of?

You need to ask him if its a posi or an open type carrier. If its posi, find out what type of posi it is as there are several types and they are not all the same. If you use his gears you will need a new carrier, whether you get his or another one.

The other concern is the spline count as BGH mentioned, and I forgot about in my first post. If the carrier does not have the same spline as the axles in your rear then you will need to get new axles to match the spline count of the carrier.

so i cant still use my posi than? and how much would a new carrier be you think? im only 18 and on a budget lol

No, your posi carrier won't fit the new gears. A new posi carrier usually starts around $350 and goes up from there I believe.

yikes ok looks i got some saving to do lol

My Camaro has a 3.42 non-posi drum rear in it now. I don't have a lot to put into mods or upgrades on it. That's why I ended up buying a 4thgen posi disc rear at the local junkyard. I paid $110 for it, complete from rotor to rotor. I am in the process of installing a set of 3.73s in it before I put it in my Camaro. Or at least I was until I had to put it on hold to get the house ready to have the family over for Christmas I got the gears at the same yard on a different trip, paid $75 for them. Not only did the gear/posi swap end up being cheaper for me than buying a posi carrier new, but I also get to upgrade to disc brakes in the same swap.

Might be something to look into. Good used 4thgen rears typically go for less than just the cost of a new posi carrier.

You can get the thick gears to fit your 2 series posi for about $180 and the installation kit is $96. If these used gears do come with a posi then you need to find out what it is. If it's a Governor Lock then you probably want to pass on it. These tend to break when abused. If it's an Auburn then chances are that it's worn out or close to it. If it's a Torsen then it would be good, but it woudl also be 28 spline, so it wouldn't work with your axles.

well i was lookin at summit and i found the gears i think i need, 373s, 26 spline, and series 2 carrier, shouldnt this work since its a 2 series carrier?

The axle spline count doesn't make any difference with the gears, just the differential. Yes, you need gears for the 2 series differential.

so if i wanted i can just go buy those gears from summit than?

Yes, but don't forget the installation kit. You will need it to set up the gears.

cool thanks a ton i now know more than i did 24 hrs ago lol