the IROC rearend is limited slip 3.08,my spare is a one legged RS also out of an '89,are the axles same splines?can I use my posi chunk in the other rearend ?axles interchangeable??

 

89 is the transition year when they changed from 26 spline to 28 spline axles, so it's a tossup as to how many splines for each rear you have. If I read your post correctly, they're both 89 rears right? Anything 90 and newer is guaranteed to have 28 spline axles. From what I've seen, the vast majority of 89 rears are still 26 spline, but this isn't very reliable. Also, it's highly unlikely that the housing tubes are bent. If your wheels are wobbling excessively, it's almost always due to bent axles. If the axles end up being different spline counts, just scrounge a good set of used ones up, or buy a set of Superior brand replacement axles. Superior axles are stronger than the stock ones, and they're machined pretty much identical to the originals, unlike Moser and some of the other brands. I had a bent 28 spline axle in my 91 3.23 disc rear, so I grabbed a 28 spline drum brake axle for cheap from a 90 V6 car at the junkyard, and it worked perfectly, even though it was a drum axle. The 88 and older disc axles are different from the drum ones, but 89 and newer are the same from what I've found.

 

thanx,yes both are '89,and both are drum brake rearends,guess it's a 50/50 on the spline count since i've not pulled either apart,sine it's drum rear,doesn't that mean it has the auburn chunk,not a borg-warner?the tubes could be bent the original car was hit so hard we couldn't save the body,damage from passenger side almost all the way thru to driver side

 

Wow, judging by the pic, I suppose it is possible one of the tubes could be bent. I remember seeing that pic on another post here about a year ago, and feeling really bad for you. If both rearends are 10 bolts, then it's definitely an Auburn posi. The Borg-Warner posi units only came in the 9 bolt rears, which were built by Borg-Warner. The only other possibility in a 10 bolt would be the Eaton Gov-Loc, but I'm pretty sure those were phased out in the f-bodies by about 86 or 87.