tbfirebird

what camaro of firebird's came with 3.42's with a posi in the rear that i could just bolt up to my 89 firebird formula 305 tbi with an automatic 700r4 i got drum brakes in the rear.nd i just want to be able to bolt up the rear end up.

Morley

Any that were ordered with drums and posi with 3:42's will have them. There is no cut and dry on which had that setup. And since posi was only "required" on disc brake equipped third gens, it will make it that much harder to find a drum & posi setup. You'd need to keep your rearend and just swap out the carrier & gears (making sure the axles have the same number splines as yours)
For that way, the 1991 Formula's came with 3:42's and limited slip.

85IrocNOH

posi wasn't required for rear disk brake equipped thirdgens. my Iroc has a 3.42 non-posi rear with factory 4 wheel disc brakes.

Morley

Sorry to disagree, but it was. If you ordered 4 wheel disc you HAD to get the limited slip. i know because I ordered my 85 option by option and had to get limited slip because I wanted 4 wheel disc.

LT1guy

iTrader: (1)

I have two disc brake rearends from 84 Trans Ams, and neither one has a posi. Sorry, discs are no guarantee of anything else, at least in the third generation. It makes no sense to me that someone would order rear discs and non posi, but apparently they were built that way.

RB83L69

Same here.

What may have been true in 85 is not necessarily true in all years and all car lines.

It's extremely difficult to find a 3.42 posi for one of these cars. There were very few of them in the first place, and they would have come specifically in 89 or 90 up 305 TPI 5-speed cars with G92; and they would have disk brakes. That leaves a very small universe of them to pick from. That's one of the most desirable combos out there. I doubt any of the few people who have them is going to give it up unless they've wrecked their car and they're parting it out; in which case you have a very small window of opportunity to get there before any one of the thousands of other people looking for the same thing beats you to it. And it probably won't be cheap.

However, it's very easy to find 3.42 drum brake one-wheel-peel rears; since that was a pretty common combo in 6-cyl cars. If you find a 90-92 one of those (so you guarantee yourself of getting 28 spline axles), and add the SLP posi to it, you may find that it's a whole lot cheaper and less trouble than all of that other stuff in that other post you have going about this same subject.

LT1guy

iTrader: (1)

Or just buy a 94-02 F-body rear from a 6 speed car; they're all 3.42s, all posis, and all have disc brakes. They bolt up the same as a third gen rear, you'll have the "good" brakes (93-97 similar to the 88-92; 98-up better still), and they're generally no higher than a third gen disc rear (typically about $300-350 complete). They are slightly wider, but its only noticeable when parked beside a car with a stock rear. With stock offset wheels it doesn't look bad (or you can run 4th gen style wheels, but you'll need a spacer in front), they're just more flush with the wheelwell.

Morley

For the doubters I pulled this:
1985 Z28 Special Performance Package






Other Views:

Engine: Base engine was LG4 305 w/ 4 barrel Quadrajet. Dual exhaust.

Transmission:

Clutch: 10.34 inches

Rear Axle: Positraction (G80) manditory when equiped with 4 wheel disc brakes.

Brakes: J65 4 wheel disc brakes available.
From this site http://www.iroczone.com/specs/camaro/camaro85.html

Notice the word "manditory"?
Check it out, says the same thing for every year they listed...82-92

tbfirebird

so a rear end from a 4th gen will bolt up to my rear end if so im just going to buy a 4th gen rear end how much do the tires really stick out than the stock cuz i was going to run 275/40/17 or 18 and i just want to know if it will fit personaly i like the way it looks but i dont want it to stick out to far.

LT1guy

iTrader: (1)

I have no idea what was mandatory or not on Camaros, but it was possible to get discs without a posi on TAs. There are exceptions to everything, esp as far as cars are concerned. Just because its in print doesn't mean its correct.

RB83L69

"But it must be true. I saw it on the Internet!!"

That page is known to be riddled with errors. I would not quote it as an authoritative source, when there are plenty of cars running around that contradict it.

And he even mis-spelled "mandatory" when he typed that in.... highly unlikely that it came from GM themselves.

Morley

And just because you don't have information someone else has, don't dismiss what they have to say as wrong.
Seems to be a lot of that going on here lately.

joshwilson3

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85IrocNOH

Sorry, but RB83L69 is right in both cases. Just because someone puts something on the internet doesn't mean it's right (in most cases it isn't). My Iroc is proof that you and that website are both wrong. I still have the original rpo codes under my center console to prove that it DID NOT come with a posi rear but DID come with rear disk brakes. I'll get a pic of it when i'm home after this quarter ends and post it for ya.

Just because you hear information second-hand, don't assume it's the truth and go passing it off to other people. there IS alot of that happening on this website.

Morley

Can't swap axles, the axle tubes for the 4th gen will also be longer.

What you can do is get rear wheels with back sapcing that will allow the tires to sit in a more normal position.

To swap to disc's you really don't need to swap the whole rear, but it'd be much easier to do so.
What you'd need is the entire rear howsing assembly (with calipers and such on it if you can) Emergency brake cables from the wheels to the center tie in point and possibly brake lines and hoses (pretty sure you'd need 1 line and 1 hose) Also you'd need a proportioning valve for 4 wheel disc.

I thnk thats about it. If you go junkyard for the rear assembly you'll want to get caliper rebuild kits for the brakes (the rear calipers are EXPENSIVE the last time I checked) and I'd also get new rotors (about $50 each)

Either way you go its going to run into some money to do it right.

Morley

I wouldn't exactly call hearing it from GM when ordering a car as "second hand".
So when I ordered my car in 85 and GM said that to get rear disc's I needed to have limited slip, they were wrong??
Don't think so, but nice try.

Truth? Truth is I don't give a damn if you want to believe it or not, I was merely trying to help someone be able to track down what they were looking for.
P.S. I still have the original order form for my car, you want me to post a pic of that?

P.P.S. I'm not going to argue this, I'm the one who ordered my car, so I ought to know what was said and what wasn't, after all I was there.
Bye, bye, no more replies. Have a nice day

joshwilson3

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85IrocNOH

morley, was your camaro just a z28 or did it have the iroc package also? that may be where the difference lies. i'll post in the history forum and see if there were any situations where a posi rear was mandatory with rear disk brakes.

Morley

IROC
Was also listed in the Consumer Reports "New Car Buying Guide" (the little book they used to put out once a year with car prices and option prices) as having to have the limited slip with 4 wheel disc's.

Morley

That would work, but the limited slip of those years were junk (if it is still the same on that came with the car). They had a tendency to "grenade". My limited slip governor "exploded" with 35k on the car and trashed the rear pretty good. I met a guy that owned an 87 IROC and worked for GM's customer complaint dept., he said they got calls almost every day about the rears in the mid 80's third gens shelling out, his let go with 5k on the car.

Whatever you get, get it with a 3 series carrier (3:27, 3:08, 3:73 etc) that way you'll be able to put in the 3:42's you want without having to change carriers.

joshwilson3

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tbfirebird

is there any certin car from 94-2001 i should get the whole rear end from and is there anything else i should grab?????also was that the only option a 3.42 posi or is there a different ratio rear.Am i going to have to modifiy anyhting ive got drums in the rear not disc and the rear im getting has disc dont i have to get a certain valve or something.

lb9mm5

All I know is my 89 Formula T-5 came with the B&W 3.45 rear(GM3) I don't know if it's better or worse than the 3.42 rear(G92) (Both being posi, of course)Does any body out there have any clue?

lb9mm5

I just can't seem to find any info?

LT1guy

iTrader: (1)

I didn't dismiss what he said as wrong; I merely pointed out that you COULD get a non-posi disc rear, at least in a TA. The comment you quoted was a more general one. I have owned two of these rears, so I know they exist...I didn't just read about it, or have someone tell me its true.

RB83L69

That's usually considered one of the most desirable rears to have.... the 9-bolt is generally stronger than the 10-bolt, it has a good ratio as compared to the 305 & 350 auto cars which came with as poor as 2.77s and 3.23s at best, plus it's 89-up so it has the PBR disk brakes instead of the crappy Delco ones.

The thing about the posi units that explode also applies to the ones in the S trucks, which interchange into these cars with 10-bolts. It's the Eaton Gov-Lock, affectionately known as the "Grenade Lock". Sometime in the later years GM started using Auburns in these cars' 10-bolts, which are better than the Gov-Lock, though still not really heavy-duty; then in 98 they switched to the lighter-duty Zexel unit.

Lots of misinformation gets posted around here all the time. It always amuses me to see people who refer to some random site on the Net or an enthusiast book or a magazine article as the absolute reference truth; or who have one little tidbit of info about some one or another of these cars that might possibly be true about one model or year, but may or may not apply to them all. Fortunately most of it is mostly harmless, although not always; in this particular case it might lead to some impressionable less experienced person paying too much for some rear because he thinks that it has posi just because it has disks, and he gets one of those that doesn't have posi. It's too bad that it's basically impossible to guarantee the factual accuracy of what people post here. It even extends to pure science and other similarly indisputable fact, as well as historical details like this.

"It is better to be merely thought of as a fool, than to open one's mouth and remove all doubt."

joshwilson3

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LT1guy

iTrader: (1)

Everything is different between the two rear disc systems, but the housings and the axle length are the same so you could install later-style brakes on the early rear, at least on the 10 bolts...I have no experience with the 9 bolt.

Morley

The Moraine calipers were set up wrong from the factory. If you get the "recall" kit and fix them they will work fine ($40 for the kit)
Not sure but you may have to get a new master cylinder (another $40).
The brake lines...depends on which line you need and weather you plan on just making your own. The hoses cost about $20 each.
The E brake cable would probably have to be a junkyard find or if you know someone with the same moraine brake setup you could "borrow" their cable and have one made using theirs as a template. All you need of the cable would be the piece that goes from left to right and hooks to the center cable.

gen3z

man i am late for debate on this one...a freind of mine got a 92 z28 off the dealer new and we did the same mods as our cars his car lost every race by 5-7 cars we soon found out the car had a non-perfomance axle ratio rear end it was a friggin 3.08 non posi,who was the fool to order a sports car with out the performance axle in other words you really cant take it for granted the rear is always what it should be,the worst is the 4th gen z,2.73posi disk,first gear lock-out at least the LS1 cars were more specific 3.23 or 3.42 of course not all posi,but you get disks and gear!!!!!!!

pasky

Incorrect sir, My brother in-law has a 95 camaro with drums, not sure about posi, his is v6 with stickshift.

theratdude64

IM pretty sure thats what my 2.8 V6 has...

LT1guy

iTrader: (1)

Not incorrect..read the post again. I said "Or just buy a 94-02 F-body rear from a 6 speed car; they're all 3.42s, all posis, and all have disc brakes"...if the car in question is a V6, it isn't a 6 speed. I didn't mention the V6 cars.

fb305svs

Wow, i thought 89 on up disk brake rears were all gm 10bolts?

what were the years for the bw rears?


btw, i have a 92z28 rear, tosion posi, 3.42 gears, pbr 12 brakes...


id be willing to part with it for a trade for a 12 bolt lol..

johnjm22

I have a 91 305 TBI with a T-5 and 3.08 Gears. Would the 3.42 gears from a 85 2.8 MFI work in my car?

pasky

Oh, woops, could have sworn you said v6, my mistake.

LT1guy

iTrader: (1)

Are you just using the gears, or the whole rearend? If the whole rearend, yes; just bolt it in and go. It will be slightly weaker due to the reduced spline count though.

I'm not sure where the break is for 2 and 3 series carriers in the 7.5/7 5/8 rears, but as long as both are 3 series carriers the 3.42 will work. An easy way to tell is if the 3.08s are noticeable thicker in the ring gear area than the 3.42s (3.42 definitely has a 3 series carrier); if they're about the same, it will work. You can't use the 3.42s and their carrier in your rear because the spline count is different, 26 vs 28. You could use a three series carrier from any fourth gen (like one of the SLP takeouts, not available anymore but someone may have one) in your existing rear with the 3.42s. As an alternative, if your carrier is two series, you could use a ring gear spacer (available from Moroso and others), or buy aftermarket gears for the two series rear (thicker than the factory three series gears to compensate). Or, rob the guts out of any of the above mentioned 4th gen rears..posi and gearset. That should cover all your options

Zepher

iTrader: (1)

This is a confusing thread.
So, is my rear in my formula rare, it's a 3.23 Drum Posi rear.

Also, 2 series gears are beefier than 3 series. I don't know if that makes them stronger or not, but they are beefier.
It took my brother 6 months to break them vs the 2-3 months that it takes to break the 3 series gears.

johnjm22

Well I wanna keep my current rear end becuase I hear the 91-92 rear ends are better than earlier years. But from what vehicle could I pull 3.42's from and have it work in my car?

WS6Formula305

My Formula has the 3.23/posi/drum rear in it too. Originally an LB9/auto but now it's got a healthier 350 crate in it. And it's waiting on a new Pro-Built transmisison because the stocker doesn't like to find 3rd gear any more.

sr.bond

just out of curiosity,my 1982 z28 has a 3.42 with drums and its a posi.

johnjm22

Does anyone have a picture of a 3rd gen with a 4th gen rear end int it?

Zepher

iTrader: (1)

4th gen rear installed

johnjm22

Looks good!!!! You can't even tell.:hail:

posbird87

my 87 formula had an L98 and disc posi rear. whats the ratio? 3.42's?