So a local guy posted that he is parting an 88 IROC with a posi rear disc rear end. I asked him what he wanted for the entire thing caliper to caliper and he respond with $400 saying that it has aluminum calipers that were only available on IROCs and GTAs. So I did a search here and the closest I could find to this were listed in the classifieds for around $150, there are 2 1LE complete rear ends listed for around $350. He is under the impression that since it has aluminum calipers its better than a 1LE. So whats this thing really worth? I have been contemplating this swap, but in the long run it may not be worth it. I offered the guy $125 and he took it as a huge insult. (seeing that there are many in the classifieds for $150 I didnt think I was off base.)

What would I need to just swap rear discs onto my one leg wonder drum rear?

 

if it is stock the aluminum calipers is the 1LE brake option. this is a pretty good option. and depending on the rear and its shape... has it been rebuilt? and mods? did he upgrade it?

350 wouldnt be that bad a price depending on the condition of the rear. 125$ would be dirt cheap for a 1LE. the brakes alone are worth more than that as an upgrade to stock disk/drums.

as far as upgrading to the disks its more trouble than its worth for a stock setup. better just going all out and getting a newer 1LE setup/or baer or 4thgen/corvette brakes. u need alot for the swap. new calipers/rotors/pads/ lines/ the caliper brackets/ all the brakets/ proportioning valve and i think EBrake cables

 

Be aware that worn posi cones and carrier are a chronic
problem with the B/W 9 bolt axles(of the 3 i have tried
all have been bad) they still work with the bad cones
but the oil gets contaminated with minute metal particals that damages the bearings some and further
wears the posi-if i was to use a 9 bolt i would install a
drain plug in either the rear cover or the case and
change the oil at least once a year,put a magnet in
there too(well secured of course)
On the plus side the the 9 bolt has very strong axles
H/D axle bearings,4 spider pinions. Weakest part is
the ring+pinion (7.75") which is only slightly stronger
than the '85+ 7.625 10 bolt gears. If posi can be
verified as good(along with bearings and gears) I'd
say it's worth $400

 

i was told that u cant rebuild the 9bolt posi along with the 10bolt posi... u just have to buy a new setup. the 9bolt is stronger than the 10bolt which is why they stuck them behind the 350TPIs but the posi get worn out in them, cone posi are the worst, even the auburns bc they leave alot of CR@P in the rear that gunks up the oil and bearings etc.

my posi is bad in my 9bolt. i only have rubber on one rear fender from the dragstrip

theres a way to test it. u put a tq wrench on the passenger wheel with the rear in the air and have sumone hold it, set wrench to 35ftlbs(i guess on a lug). then put a lug wrench on the other wheel. then turn the wheel if the other side cant even click the the tq wrench at 35ftlbs the posi is basically shot. if it does click it then try a higher setting like 40-45ftlbs. the higher the number that it turns the better condition the posi is in. if it cant click it at 35lbs, then u ask for a lower price. then spend 400-500$ on a new posi.

 

i gotta question that is really stupid.. like REALLY dumb.. but im going to a yard within a few weeks that has camaros and s10s etc, how can i tell if its a posi rear end by lookin at it? i got an open diff.

 

unopend rears with posi have a tag(small rectangular) on the rear cover. it kinda sticks out metal(they were painted yellow) its under the rear cover (usually facing the pass side) sandwiched around one of the bolts but under the cover.

other wise there is a rear diff code on the driver axle tube that has a code on it. if u can write it down ud have to decode it. bring a haynes manual (think the codes are in there) and easy test would be to (in the rear was in the air) to turn the passenger wheel if the driver wheel also turns in the opposite way then it has a posi. i believe if the other wheel doesnt turn then it doesnt have one.

could also see if the car still has RPO codes in the center consol and rely on that but it could not be the stock rear. easiest would be to look for the tag, then decode the rear code then do the wheel test. in any order

 

1988 9-bolts did not have Aluminum PBR calpiers and 11.655 dia rotors. Also no such description as 1LE rear brakes, just something sellers add to jack the price up.
I would not pay more then $300 and only if it was a true 1989 rear. Anything earlier, about $100 for the iron calpiers & 10.5 rotors.

 

All the pro's & con's above are probably valid, but I can't find where
IrocZ_85 identified the version. So my is that needs to be
the starting point. Is it the 9-bolt BW, or the 10-bolt (generally
Auborn clutch cone carrier). There are supporters & detractors of each.
I just paid $350 for a 10-bolt Auborn unit: large 28 spline axles, and
split clutch cones, as referenced above.

In short, I think $400 is a bit much. Do some shopping around, and
become familiar w/ the various configurations available. Then you'll
know if someone is trying to blow fairy-dust at you. From experience,
I can say never but the first one -- there'll always be another deal
as good if not better, and you'll be smarter.

The brake conversions are just not cost effective. For the price
of conversions, you can buy any junker disc axle, & completely
over-haul it. I have receipts to prove this...

Good luck,
kk

 

Sorry guys, all I know its that he says its a 3.27 gear with aluminum calipers. I'm not going to take the time to drive out there and check, the guy thinks he has gold and it doenst matter what I tell him or whats actually in there, he thinks its worth $400.
I thought 1LE rears had 3.42 gears or something close to that......

He said nothing about the condition and I am sure he would have told me if anything was new to try to justify the price.

 

Without knowing how long the "drive" out to "a local guy" would take,
it might be worth doing to just to see it & gain some general knowledge.
Take the cover off, & you can quickly determine the ratio, and
carrier type. Remember, the princess had to kiss some frogs before
finding Prince Charming.

 

I think I have learned all I need to know from whats been posted on this thread.......

 

Last one I sold I got $300 for it.I also sold a Dana 44 disc rear for $350(at the time I didnt have a 3rd gen to put it under) Now every time I think about it........................I swiftly raise my right foot and kick myself square in the A**!!!!!