I have an 89 IROC with a rearend out of a 92--10-bolt (I think--pretty sure) with 3.73 aftermarket gears. The positraction seems to have quit working last weekend at the dragstrip. When I did my burnout before the pass and one test burnout on the retuen road, the left side is no longer spinning.

Is this a rebuildable type unit with clutches?

If not, what type rear end posi unit is it?

Even if it is rebuildable, is that my best choice, or is there an aftermarket upgrade that would be better? The car is a daily driver (kinda) with an occasionally trip to the drag strip.

I have done a couple searches and been reading but am more confused, because I'm not sure which type rear end I am dealing with.

Can someone please educate me, and/or point me in the right direction to a tech article or thread that would.

THANKS,
Craig

 

You've probably got the auburn posi unit in that rear, which is a cone clutch style posi, and is not rebuildable like the eaton units. A couple of guys on here say they know how to rebuild them, but obviously it's not a standard deal to do it. If the rear you have is for sure out of a 92, you should have 28 spline axles. A good option is the zexel-torsen posi carriers out of fourth gen axles, which are 28 spline units. These use gears in place of clutches in the posi and are said to be pretty durable. You can usually find them fairly cheap in the classifieds here or ebay.

 

THANKS!

What would I look for to confirm that?

The heads are coming off this weekend and going to the shop, so I'll be able to mess with the rear end while they are at the machine shop.

I was looking around at Summitt posi stuff (still not quite sure what I'm dealing with), but if that is the rear end that is in my IROC, which would I be looking for and what would be a good replacement unit to get?

THANKS for everybodies help and advise!

Craig

 

If money's not a major issue, I'd recommend the eaton posi unit since it's rebuildable and pretty stout. They run about $400 the last time I looked at them in Summit. You'd want the one for a 7.625" ten bolt with 28 spline axles for your application. I've seen them a little cheaper brand new on ebay. If you punch in "GM ten bolt" in the search bar, a bunch of them should come up. Good luck!

 

THANK U VERY MUCH!!!

Installing this unit, would it be necessary to set up rear end clearances again, or would it be just replacing/swapping the part and go back with the same shims ETC?

If it does involve setting the clearances again, is it cool to re set up the same gears after a wear pattern has already been established?

Craig

 

I'm no expert on rearends. I've done a couple of them. If you make sure to keep your shims in order when you take them out, you should be able to put them back in with the new carrier in the same order and use that as a starting reference. This should get you in the ballpark, or if you're lucky, maybe even get it perfect. But yeah, you should re-install your original shims and then make sure to check the wear pattern with marking compound and and also check the backlash with a dial indicator to make sure everything is in spec. If not, you'll have to add or subtract shims accordingly. RB83L69 is one of the most knowledgeable guys on the board when it comes to setting up rearends. You can send him a PM if you need more expert advice. I noticed "Mr. 3.76 Ratio" sorta hijacked your other thread but RB should be able to help you out.

 

Thank You!

MERRY CHRISTMAS!!!