I have an 85 Z28 with a rear off of an 85 firebird. The original rear grinded to hell for some reason, but this one seems to be working just fine... except for the fact that its open! I believe the gear ratio is pretty much the same as the original, but I dont know the numbers. I really want to make it posi but thats where I need some help. Can I just put a limited slip cone type differential thingy into my existing rear differential and get posi? How exactly does that work? If not, then how can I get posi for under $1200 and where? Any tips would be greatly appreciated! I think it will help my launch!

 

Just make sure what series of gears you have, 3.08 and lower numerically is a 2 series and 3.23 and numerically higher is 3 series, then purchase the Posi you want and the rebuild kit. Should cost around $500 for the parts and labor can be anywhere from $150-500.

Another alternative is to buy a complete posi rear end and put the entire thing on your car. Should be less than $400 for a perfect rear.

 

Hey thanks man! So are they fairly easy to install? And if I can get a complete perfect posi rear from drum to drum for $400, PLEASE tell me where!!! I havent had any luck finding one.

 

Changing to a limited slip carrier is not a easy DIY job which requires a gear & pinion set up. Also expensive for parts & labor.

A complete rear, you will have to do a lot of searching. E-bay, sale boards, salvage yards and etc. Again the cost of the rear & additional parts can also be expensive.

So is it worth it?? My opinion is no, if all you want to do is burn two strip of rubber.

 

ya but the problem with junk and salvage yards is that u dont know what the hell the last person did to it. i would prefer something new but they cost a grip! i know how to replace a whole one drum to drum cuz i did it when my original died. i would be ok with putting the LSD in myself, im just looking for input from people with a lil more experience than me. but heck ya its worth it! it looks wimpy when u burn em and only one side spins! plus at the quarter mile, i lose too much time and traction with the fishtailing!

 

so does anyone else have any input? I'd love to learn more....

 

this is a big job an is not as easy as pullin one out an slappin one in your gonna need a press anyou are going to need to know how to set the lash an back lash plan on spending a grand an if you dont have someone to show you how or talk you through it 1500 ten bolts are whimpy an if you are going to pound it you are looking at more then a diff swap so when you think in performace an strength talk to moser or somebody that specializes in them. sure you can just throw a limited slim in it but you will break it believe me been there

 

Don't let these guys discourage you from swapping your own carrier. The pinion gear will be untouched, so the only special tool you will need is a dial indicator for measuring backlash. If a press is necessary, I'm sure there are shops close by you with presses. Worst case is old bearings off / new ones on - $20 to $30. No big deal. If you decide to go through with it there are more than a few people here that will help you through it.

 

Just a few minor details from the easy DIY gear Change.
Axle shaft count.
Limited Slip Carrier for the Gear 2 or 3 series.
Correct LS for axle shafts
Or in your opinion, just go at it .

 

your exactly right all i was trying to do is let him know is alot of these rear ends have been torn up an what it cost to build one up to take some abuse an then they are still only good for about 425rwhp i have this setup in my car but im not doing a regular grind at the strip or crazy burnouts from hell. all i was saying is look at all the options so you dont get disapointed. bye the way the auburn pro series is a good unit for the price ive worked for them for many years an have never had any problem with one good luck with the project.

 

For clarification - "just go at it" with the correct parts.