The cars an '89 IROC 350 700R4. G80 2.77 w/ discs. Basically looking at pulling one from a junker and bolting my discs on, say a 3.27 or 3.42
How many have done it?
Please list any and all challenges with this idea. Thanks Guys.

 

All 3rd gen rears are interchangeable, 9 or 10 bolt. However the mounting plate for the brakes is not. only ratios you may find are 3:27 9-bolt (some are still out there) 3:45 9-bolt ( Rare- good luck on this one) and 10-bolts that are common 3:23 & 3:42 All rears from 350 TPI will have a Limited Slip and the 3:42's may not have them (except 305 TPI m5 with RPO G92) the others are from v6 cars and few had the G80 limited Slip option,

Just remember you now have a 2-series 9-bolt that cannot be upgraded to another Ratio. My opinion is if nothing is wrong with your present rear, leave alone and spend the money on something else. If its not broke why fix it.

 

Your big problem is finding a 3-series 9-bolt carrier with a working Limited slip. New parts are slim to none, 9-bolt.com is no longer in business and that was a source that no longer exists. Again the big problem for the 9-bolt is finding parts.

 

Were there ever any 10 bolt rear disc brake axle housings? That might be a better way to go to retain rear disc brakes. And then, of course, available axle ratios become plentiful once you're playing in 10 bolt world.

 

^Yes, there were 10bolt rear disk axles

 

And there was a 3:73 ratio option in 84. I doubt there's many around though.

 

Actually the nine bolt is still in production. It is made by Borg Warner of Australia. Parts are available in the US but cost more than the 10 bolt. The toughest gear to find is the 3:45 gear. 3:27 and 3:70 are not to hard to come by. A friend just scored on a 4:10 gear for his. The 3 series carriers are available. There are good posts on the subject over at www.thirdgen.org.

 

Thanks for help guys. Here's the thing , I brought the car from So-Cal and I'm really feeling the 2.77's up here. I'd like to do the swap cheap, and for around $65, I can pull a rear from one of the many cars in one of the many junkyards around here. So whats all needed, parts and fabrication, for my discs to fit: 1) A 10-bolt G80; 2) Another 9-bolt w/3 series; 3) All other options welcome

 

Swap in some 3.73's if you can. It's my favorite ratio! If you lived near Michigan you could come over and get my old 10-bolt axle housing and build yourself something.

 

not that hard to find 9 bolts, I've got 3 right now and had another before,
none are for sale

couple 3.27s, 3.45 and had a very rare 3.70, my moron brother sold it for a set of 16" iroc rims with no tires

not 1 with PBR brakes though, but my cousin just picked up a 3.45 with PBR's for $400cdn

you just got to know what cars to look in, check 85/86 TA's for the 3.70

 

you need a 3.23 and up carrier,

if you got 2.73's or 3.08's in your 10 bolt your screwed you need a new carrier

 

ALL 9-bolts are discs right? Never drum. Also, what does it take to swap my discs to a G80 10-bolt(drum or discs)?

 

ring-pinion.com has 3.73's for the 9 Bolt Borg now. I just spoke with Jason there and the install kit is $165 and the pinion set is $165 also. His ext. # is 5586. I'm ordering after I speak with my mech. Ring-pinion said the gears would make a howl or whine sound. Does anyone know about that?????

 

They're not 3.73's, they are 3.70's. I bought mine from ring-pinion.com and yes they whine from 55-65 MPH when cruising.

To upgrade a 2.77 9-bolt rear end to 3.27 or better, you will need a new 9-bolt 3-series carrier posi unit, and new gears. That'll cost about $600-800 dollars, if you can find the parts. I think you can swap 9-bolt and 10-bolt disc brakes up to 1997. I know the 1998+ LS1 rear brakes will fit on a 10-bolt but require modification on a 9-bolt.

 

So my '89 discs will swap onto any 3rd gen 10-bolt, with NO modification?