Hi guys. first time posting on this board. i have an 88 iroc with a tpi 350 and 700R4. the car has disc brakes and posi in the back. the rear is starting to go non-posi on me. i'm running a 2800 stall converter and am going to install a lpe 219/219 cam. I took the rear in to change the fluid and i pulled the tag off the rear. now my car is supposed to have 3.73 gears but the tag says 2.72. what is up with this? what rear do i have? is it the australian rear? i want some 3.42 or 3.73 and maybe a new posi. what course should i take? can i use a 4rth gen rear? i have money but i'm not made of it. i want to keep my disc brakes and the current offset.-i just spent alot on a set of centerlines. bring on the advice!

 

here

 

SON OF A........... I can never post a pic.

 

if the car came with the 350 tpi and has disc brakes iam going to say u have the 9 bolt rear, easy way to find out is how many bolts did u take out to get the cover off was it 9 or 10. u can not use a 4th gen rear end and keep the same offsets, the 4th gen rear sticks out about 2 inches farther on both sides so it will change the offset on u, that is why we need the adapters to put 4th gen rims on the 3rd gens to get the stock with bad, the parts to rebuild a 9 bolt are somewhat costly compared to the 10 bolts but if u go to 9bolt.com he can answer all ur ?`s for u

 

All right, crawled under the camaro this morning and i see nine bolts. 4 across the top and five around the bottom. cover is sort of square in apperance. this is the 9-bolt borg warner or "australian rear" correct? do I build this or look in the junkyards for a 10 bolt? are there different series of 10 bolts?

p.s. i though the 4rth gen rears were narrower than the 3rd gens and nessesitate the use of spacers to use under our cars.

 

From my experience: Up to moderate power levels to around 500 horse/500 lbs-ft (which is alot for a street car). You're better to stick with what you have, assuming you're okay with the gear it has in it. The 9 bolt will hold whatever you can throw at it longer than any 10 bolt will as long as you don't exceed those limits. However, if your dead set on putting a lower gear in it as you thought it already had, you're gonna spend more to achieve that with the 9 bolt than you will the 10. Even if you go the cheap route and score yourself a good deal on a used 3 series (3.27 ratio up) carrier from ebay or a junk yard, and buy a 3.70 Yukon Brand gear and install kit from Randy's ring a pinion; you'll get out a good bit more than what you'd find a good deal on the equivalent 10 bolt parts for. Keep in mind though, you'd have to find a 10 bolt replacement to start with. So you'd be close either way.
However, if you have big plans for the car and intend on building a powerful motor, using nitrous, a manual tranny with a good holding clutch, and a low gear.....you're gonna have problems no matter how much you built either one.
It that's the case, you need to consider a bolt-in 9" rear or at the very least a 12 bolt or dana44. Dana's are overpriced due to rarity and not much stronger than a 9 bolt, so that would be a foolish way to go. The 12 bolt cost about the same as a 9" )new or used) and is not quite as strong as a 9" and harder to change gears in. Now alot of people will tell you that a 9" robs alot of power. Yes it does compared to 9 or 10 bolt, but so does a 12 bolt. The 12 bolt will only be 2-4 hp less than the 9". You'll have more strength, ease/convenience when changing gears by having a removeable centersection, and no matter where you are on the planet....you'll find any part you need for the 9" to get going again in any parts store.
I like 9bolts (if you're within they're capabilities), but don't be an idiot like me and put a bunch of money in one and then realize that you're intentions for the car are alot more than what you first thought. I'll be out a buch of money when this thing grenades and still have to buy something STRONG!
I wish I had jumped at the chance now for one of those used Moser or Currie bolt-in 9" rears I passed on before I sunk money in this 9 bolt. The $850- $1000 dont seem so bad now.
If you want to use the 9 bolt, wait a few monts to see if the 2 series gear sets will be available so you don't have to buy a 3 series posi. That cuts the cost down ALOT.

 

To answer your second ? Yes, 4th gen rears are narrower and do require spacers to bolt factory style rims, or require a certin amount of offset/backspacing if you use a custom rim. 90-92 10 bolt rears with 28 spline axles are just as strong as the 4th gens 10 bolts, you just don't have the provisions for ABS (which you can't use) and you don't have to buy spacers. Neither are still as strong as a 9bolt until you put HD custom axles, solid pinion spacer, and an aluminum girdle/support cover on. Not to mention, if you still use the c-clips.....if the axle breaks, you're gonna:
1: Destroy at least the rear quarter panel of your car.
2: The above plus wreck and hurt youself or someone else.
3: Or, even worse die, and maybe even kill someone else.

9 bolts have bolt in style axles (like a 9" rear) and aren't prone to the c-clip failures that sometimes happen to OEM saginaw rears (10 and 12 bolts).

Food for thought for ya.

 

Thanks, just got off the phone with a local buddy who has a low mile 9 bolt with disc brakes. he pulled the cover and tells me he believes it to be a 3.27:1 now i can grab this for $175.00
can i put 3.73:1 in it later if i like?

 

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BTW: 'drain89' there's an outfit that does 10 bolt 8.5" rears for 3rd gens. It's just another options which is a little cheaper (not that much), and the parts like you said for the 9" are everyyyyywhere, and probably a little bit more cost effective then 9" or 12 bolts.

Ron

 

Yes you will be able to install the 3.73's later with out any problems.

 

well, can i put the 373's into the 9 bolt i got now with the 272's

 

hey, cwalsh. that is very close to my setup. any time slips?

 

you probably need to check with Miles over at diffsolutions.com on wether or not the 3.73's will go on the 2 series carrier or not. I do not think it will. I believe the offset of the ring gear flange is not close enough to the pinion for proper gear mesh. I think Miles has complete gear sets w/ new posi's right now. That is what I did. Mine was a 2.77 ratio.

The last time I went to the track was last year befor the intake and TB swap and the I also had a really wore out 700R4 slushbox. Any way the best I could get was a 14.01. Since then I did the T-56, Spohn TQ arm, Accel runners, Accel base, SVO injectors and 52mm TB.

Chris

 

what was your mph? i'm doin zz-4 heads, lpe 219 cam, edel. intake, slp runners, slp headers. porting, all the free mods lca's panhard. and then it's chip burning time. want to see 13 flat.

 

Now your making me dig for paper work!!!! I found the slip it was 96.8 MPH. Also no stall with that combo I had.
Your combo sounds pretty cool. Should run well.

 

No you can't use 3 series 9 bolt gears (3.27 & up) on a 2 series carrier (2.77 & 3.08). You'll have to switch to a 3 series carrier or find a 3 series rear and start with it.
There has been talk by a couple people in making a ring gear spacer for 2 series carriers. There has been talk of making 3 series gear sets that'll bolt to a 2 series carrier as well. But I'm pretty sure nothing has come of either one.
I've seen 3 series carriers go for around $100 on ebay, but you never know what your getting.
If your buddy's 3.27 rear is in decent shape and has the pbr aluminum caliper brackets still on it so that you can swap your rear brakes right on it, you'd be wise to get it, especially for that price. Just pull the axles out of your 2.77 rear and hold them for spares incase you ever damage one. I went from a 2.77 to a 3.27 rear in my 89 5.7 IROC and it made a big difference. I think that a 3.70-4.10 would have been too much and hurt it. You'd do a fuzz better with a 3.45 gear instead of the 3.27, but you're not going to find a 3.45 rear for that price. There alot less common than the 3.27's. You're better off to just take advantage of the great deal your buddy's offering you. You could sell the axles and the pbr caliper mounts off your rear and make back most of the cost for your buddy's rear.

 

Well then, I think I will grab this 9 bolt off my buddy. I'll do it over the winter. I'll buy some gears. any reason to go to an aftermarket posi unit? should i freshen the rear up anyway? what will i need and what else can i buy to make it better? where can i get the stuff i will need? any tips would be greatly welcome.

p.s. Talked to a guy yesterday who is selling a 4rth gen rear. he says the forth gen rear is 1 inch longer over all than a 3rdgen rear. who is right?

 

allright, i'm looking around for ring and pinion sets for the 9 bolt and niether summit nor jegs carries anything. is this going to be a problem, finding parts i mean?

 

You can get all the parts you need for a gear swap,373's + install kit at 9bolt.com but be ready to pay big time for them. $175 is a great price for the 327 9 bolt. BUY IT.Unless you plan on doing a lot of drag raceing 373's are a little steep for a street car.345's are a better compromise for street & strip gears.If you can afford them and you have a strong overdrive or manual tranny you can get buy with 373's but once you see what they cost you need to decide if they're worth it.

 

4th gen rears ARE LONGER than 3rd gens,Your factory wheeles will stick out a little if a 4th gen rear is used in a 3rd gen.
Also you do not have 272's, either 277's 308's or 327's.
Most TA's and GTA's got the 327 rears and Irocs got the 277's and the only way to get a 345 geard rear was with a 305 TPI with a 5 speed.

 

well, how much should i pay for a 3.45 ring and pinion set?

 

They very in price,you can find them on e-bay for usually $200 or less but you'll pay twice that for 373's and 9 bolt.com is the only place that I've found who carries 373's for the 9 bolt. When they have them in stock 345's are high at 9 bolt.com but not as expensive as 373's but more expensive than what they go for on e-bay.The ones you order thru 9bolt.com you'll know what your getting wether thay have any wear or not etc. Thru e-bay your takeing more of a chance at buying someone's junk.It boils down to saveing money and takeing a chance on buying gears on e-bay or paying for piece of mind and getting them from 9bolt.com.
By the way 9bolt.com runs out of stock on the 345's all the time so if your in a hurry to get your rear done e-bay may be your best bet.

 

Hey !! now I have a choice. the guy who wants to sell me the 9 bolt also has a 10 bolt. it is a disc brake rear just like the 9 bolt but has 3.42 gears but NO posi. same price, my choice. what would you do?

 

Well......again it all boils down to what you want to do with the car. If you're not gonna do anything more than bolt ons or mildly build the car, and it's going to remain an automatic with stock or mild converter.....then yeah, go with the 10 bolt. And by mild I mean that. You can build the 10 bolt to handle the 12's and even high 11's easy as long as you're not putting alot of shock into it by high RPM launces with high stall converter or grabby clutch with a set of slicks that bite good. You do any of that and you'd be pressing your luck. You can get a SLP torsen diff for around $100 and a set of new gears for $160-190 and a solid pinion spacer and overhaul kit for reasonable and it'll hold up well and cost about what a set of 3.73's would alone for a 9bolt. For what you'd pay for the 9 bolt posi unit used in good shape for a good deal, you could get a support cover for the 10 bolt. If it's set up right....you could go probably mid 11's with decent traction reliably.

Just don't make the same mistake as me. I had a 350 TPI w/vortec heads and a LT4 cam (not the HOT cam) and a T56 and bought all this 9 bolt crap. Sure, with that a 9 bolts fine. Well look at my sig now and tell me how much good that 9 bolt will do me if I put a decent set of slicks on and really get in it. Keep in mind that when I get all this together I should have around 500 horse on tap and 200-300 horse nitrous on top of that.
Moral to the story is: If you told me a year ago that I'd be doing all this to the car...I would have laughed at you. Now....I should have bought a 9" rear.