mike graycar

Hi Kids! New project, I broke the rear in my convertable IROC. It's an '88 with only 70K miles. Took two teeth off the pinion gear due to failed pinion bearing. I had an '89 RS for a parts car and I pulled the rear and stuck it under the Vert. So now I'm lookin' at the busted 10 bolt with the drum brakes and I'm thinking " I could build a rear that would last and have what I want in it"

Hence my question, What would you build? It is a posi (sometimes) and has highway gears (3K at 70 MPH) and drum brakes. I was thinking about 3.42's and a decent center section. Then maybe some disc brakes (PBR/1-LE's?) All new bearings and reuse the stock axels. Good plan?

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xpndbl3

i wouldn't spend money on a 10 bolt, find a junkyard rear and swap it that way or keep the cash as a 12 bolt/9" fund some day. These people that spend $800 on a gear swap, axle swap, girdle, etc make me wonder sometimes when they're halfway to a 9" that probably will never brake.

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mike graycar

Well, I was just gonna go through this rear and make it good. The car is not fast, it's a 305. It's pig heavy and I'm not building a race car. It will most likely get a 350 or 355-LPE 219 cam and ported aluminum heads. I just want something to move the car out a little better and last in a car that's more for cruising than beating on without mercy. I have the white IROC for that!

JamesC

Highway gears? Humm, my 3.23's do 2200 or 2300 at that speed. By the way, in the tech articles, under misc modifications, there are a couple of how-to's on strenthening the 10-bolt.

JamesC

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my3rdgen

Agreed. I should know. I did it.

I spent $1450.00 on my 10 bolt. And its a piece of crap Gov-lok. I am looking at spending another $300 installing a used Torsen. I did it this way because I didn't know better at the time, and I bought all the parts peice-meal, then after it was all done I added it all up and said "S@#T! I could have had a moser 9 inch for around 500-700 extra!!"

Even if I install the Torsen, and tried to sell it I would be lucky to get 300-400 out of it, and thats with the Torsen and 3:73 gears.

I would seriously think about the Moser 9inch or 12bolt, or the Currie 9inch.

GTA matt

Lets see, i've broken 4 posi units (2 of them auburn pro series) 3 sets of gears, countless spider gears, and i haven't pulled the rear end cover yet to see what i broke friday night (probably the carrier broke in half). Get a twelve bolt. if you break 1 ten bolt, you will break another one soon enough.

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90 GTA, flowmaster cat back, hypertec chip, gmpp 1.6 roller rockers, fp regulator, underdrive pulleys, b&m transpack, accel race wires, edelbrock headers, no cats, 4.10's, moser axles, spohn adjustable torque arm, 52mm tb 1.69 60' 12.85 @105

mike graycar

Thanks for the replies, You know I've been banging around on here since '99 and I ALWAYS forget the tech articles! Thanks, I printed and read them at work.

To all the guys who are screaming "GET A NINE INCH" -I know, Whenever I'm on here and everybody tells you the same thing it's because they're right. And you are. It's just in this case I'm going for a stock/unmodified look, No heavy mods. I want to keep the car original. In looks anyway. I already have an IROC that I went nuts with and It's a lot of fun but nobody wants to ride in it. It sucks on trips. It's tempermental, rides rough, runs hot-I have over rides for the fans. Manual lock-up on the converter, Line-lock. Nitrous switches on the console that EVERYBODY wants to f&%k with. Now I've got a cage in there. I got the Vert just to ride around in. Seeing and being seen- That is what the Vert is about.

Now that being said, Who here can help me out?

my3rdgen

Sounds like my kind of car... one the wife won't want to drive!!!

I myself like the 3:73's I put in mine (had a 2:73 stock). I used Moser axles since I had a 26 spline rear and figured all the time and effort needed to find a used set of 28 spline axles would be time wasted and I would be better off with new alloy pieces that would be by far superior. I also installed an aluminum support cover. I may want to weld up the axle tubes but I have not decided on this one yet.

All the work was completed obviously with a rebuild kit and I used a new GM Gov-Loc differential (like saying I put a rotten cherry on top of my ice cream sundae). I am in the process of installing a Torsen right now and eventually down the road a few years I will hopefully move up to a 9 inch.

6speedIROC

I'd just toss a used 9 bolt in if I were you.
Good value, simple bolt in and they are strong.
You can rebuild the posi's get aftermarket 3.70 gears as well now for them.
If you don't like that I'd look in to fabricating a Ford 8.8" unit.

The 9 inches and 12 bolts are pretty pricy, you can get a good axle for much cheaper in there if you a willing/able to fabricate a little.

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86 IROC
95 LT1 & T56

Wanted: New or Mint Red Trim code 72C -> Dark Carmine 1985/1986..
seats or covers

mike graycar

I have a 9-Bolt in the white one, I am kinda looking forward to building a ten bolt because I have never done one before and I like having a new project. You believe that right? O-K, I have no life. There is the truth of it.

Anyway, Here's were I'm at:

1. Clean, Blast, and inspect housing
2. Weld axle tubes
3. Paint
4. Diff cover w/ girdle
5. Solid bearing spacer

Now for the questions:

1. I have 2.72:1 gears, Do I need to throw everything away and start with a 3-series carrier?

2. The housing will be reused right? that is not series sensitive?

3. It's an '88 so it will have 28 spline axles right? I will go count them tonight. I can use any diff for 28 spline axles then correct?

4. What posi unit is in there now? Is it an Eaton? What's better an Eaton or a Torsen?


Now, Based on what the answers to those questions are here is what I think will happen.-

Pick up were I left off in the first part of the post. Reuse stock axles, Score a Torsen diff. on ebay for a series 3 carrier. Get a 3 series carrier as well. Then some get some gears. Probably 3.42's or something similar. Finish off with a rebuild kit and try my hand at putting this thing together.

After that I will be back here asking questions about what brakes to go with. How's that?

Shagwell

diff/carrier = same thing. A 3 series zexel is a 3 series carrier. - If you do have 28 spline axles, stick with them for mild to moderate power, go aftermarket for higher hp, if they are 26 spline, go aftermarket 28. Weld the tubes, get an aluminum cover/support, depending on the camshaft/intake, either a 3.42 or a 3.73 gear, a solid pinion spacer for good measure and have fun.
Built up they'll take quite a bit, but it can quickly become a waste of money for any high powered car. I'm running 11's on mine with 17" dr's and a stick. 1.6X 60fts. Will it break? ....probably. It is built, but only because I got a hell of a deal on it as is(stocker was a 9-bolt) - Seems anything past 3.73 gears is quick death because of the small pinion.

GuitarJunki17

You guys keep suggesting 9 inch 9 inch 9 inch, and while I agree that this would be the most desireable setup, you guys that have broken your rears countless times (not just in this thread, but from what I've seen all over this board, not trying to single you out here Matt) have to think about what you are using your cars for. You guys are running 12s and lower at the track with slicks, so of course a built 10 bolt wont hold up.

But for what Mike here is using his car for, a built 10 bolt would be, I think, fine for him, especially if he is on a budget. Even with the heads and cam, he's still gonna be making just over 300hp, and this is enough for a STOCK rear to handle in many cases that I have seen, including mine.

I have been researching rears heavily in the past month, as it is time to do something about mine, as I am probably making just shy of 400hp, and somethings going to give eventually.

I'll tell you what I am doing, and you can tell me what you think. First off, my goal was to make something that can handle power, without having to change out worn out clutches (as this is what is wrong with my unit now as well, might as well be an open diff)

-Eaton Truetrac Differential DTL-912A317 - $365.95
-Alloy USA 28-spline Axles ALY-12103 - $209.95
-Richmond Gear Install Kit RMG-831044M - $128.95
-Richmond Gear 3.42 Ring and Pinion RMG-4900451 -$185.88
-Aluminum Rear End Girldew/stud kit(from LPWracing.com) 3017.5G - $190
-Solid bearing spacer (dont know where I'm getting this yet) ~$30
-Welding of axle tubes to pumpkin - Free


Grand total: $1110.73

Now, compared to paying over $2000 dollars for a 9 bolt, and making it fit, this seems pretty reasonable to me, especially since my IROC is my daily driver, and never sees track time. Maybe once a year, and I don't use slicks. Hey, some guys can afford to say "hey, spend 900$ more dollars and get a tank of a rear." But as for me, as a guy paying his way through college taking out $10,000 loans every year, this is about as much as I can manage. I'm in no way, shape, or form trying to sound like an arsehole here, but rather, just trying to make you see it from a different perspecitve.

Hope this helps you out, and good luck on your selection.

Stephen 87 IROC

Differential Pinion Bearing Spacers - summitracing.com

Part number RAT-4111 $18

GuitarJunki17

Sweet, I couldn't find it, thank you.

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355ci / 4bbl Holley 750cfm Carburetor / Edelbrock Performer RPM / Brodix IK200 Aluminum Heads / Comp XR270HR-10 Cam / ProComp HEI Distributor / Trans-Go Shift Kit / Powerstick Chambered Muffler / Summit Shorty Headers / Flowtec Y-Pipe / !Smog / !A/C

Sonix

I've also built up my rear end, with some of those goodies.

I left the axles and stock gears and posi in, but used the solid pinion spacer, summit girdle, and welded the tubes.
There's also a stud kit for the main caps, TA racing, and another company make these.

If you're looking for more strength, (or more money to throw at it, since i'm not sure this is much help), there's a tube support setup. It braces the tubes, and bolts to the rear cover. Just have to use this companys rear cover setup. I think bracing the tubes is going overboard, but it's an option. (Forget the co. who does this).

Make sure you tighten the solid pinion spacer down good, I used a 5' snipe I think, loctite the nut, and then stake it.
don't overtighten the preload bolts on the girdle. This is a wonderful invention by the way.

If your 2 series posi is still useable, you can use a higher gear ratio and a spacer. Just in case somebody in this thread didn't know this little tidbit.

Some redline "shockproof" fluid is a nice addon. Yea the fluid is pricey, when compared to fluid, but when you think it's only 2 quarts or something, and it's going into the rear for a good long time, you can compare it to bearings or something, and it's pretty cheap when you look at it that way.

Careful welding the cast housing to the steel tubes. Use a weld-all rod, or high nickel rod, if you're using a stick welder. Just don't crank up the heat on your mig as if to weld the 1/2" thick housing (that kind of heat setting), and go to town, good chance you'll warp it. A nice small stitch bead will add mondo strength as far as torsion, without warping anything.

mike graycar

Damn ! You guys rock! That is what I'm looking for!

Kevin Vandevenne

Why not just buy a used rear end out of an LS1 car? I've seen complete rears for $150-$200 locally, and they have most of all the parts you are looking for already. If you can live with the extra width, why not?

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91 GTA
355 Holley 750VS Vortec heads, CC XE276HR, 2800 9.5" converter

mike graycar

They are quite a bit wider aren't they?

trumps2000

I think the 4th gens are 4" wider.

This is how I had mine built recently, but with 3.73s, the $770 in labor and $130 for sandblasting and priming. I didn't want to spend $1100 just to take longer and mess it up. Like the rest of the car, its all a package, I don't plan to put more than 400HP in my car (260HP crate currently) and don't plan to race it often, so I figured its worth saving the $. Besides I knew there wouldn't be any fitment issue or need a weird brake setup. Just my

MrDude_1

since you're going for that stock, look...


i would snag a 4thgen rear. they're cheap because people swap to other rears all the time.... and:

you can get a econo happy 3.42 or a snappier 3.73 rear.
you would have upgraded disc brakes.
it would have a posi...
and you can bolt on 3rd or 4thgen style rims...




but really.... if its going to have a modded anything-other-then-a-305 engine, i would get a aftermarket rear. do it cheap, if you want.. a used stock ford truck centersection and a moser housing/axle/TQarm mount package...

Demon355

I can get a good deal on a '94 or '95 Z28 rear but it's been completely rebuilt with Auburn posi, strange 3.73 gears and axles, welded tubes, LPE girdle, disc brakes etc...The dude wants $700 for it. I think it's worth it.

Question is, will it just bolt in my 3rdgen? How much of a gap am I looking at here for the fenders? Will my stock GTA rims bolt up? Need all the details...

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1988 Chevrolet Camaro IROC - "Reaper"
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Shagwell

a 4th gen rear is just under 2" per side wider. - I'm running custom billet wheels, so it didn't bother me. If I were to do it again, since I may switch to a 9", I would stick with the 3rd gen offsets and keep the wheel lips closer to even.

- If you did use a 4th gen rear, you would have slightly better 28 spline axles factory, and the zexel 3 series carrier. Then you would only need the gear, install kit, pinion spacer and rear cover......

Demon355

Well it comes complete with all the things I mentioned so I just thought I'd post about what is needed to install a 4thgen rear into my 3rdgen...

So will stock GTA rims fit on it or no?

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1988 Chevrolet Camaro IROC - "Reaper"
Click here for my Garage
Toronto F-body Motorsports

mike graycar

O-K, I got the old one apart. It has 13 teeth on the pinion and 40 on the ring. That works out to a 3.08:1 correct? The axels are 26 spline so I guess they are garbage. I can put any gears I want into this rear end housing right?

GuitarJunki17

So long as they are compatible with whatever series carrier you have (2 or 3). I believe that carrier is a 2 series carrier. When you order the gears, it will specify what series the gears are compatible with.

mike graycar

All Right, I am confused. The carrier. Is that what you bolt the ring gear to or is the carrier what you put everything into when your done? Meaning, The housing is also called the carrier? I thought the carrier was the center section that contains the posi unit. Please clarify this as I was going to grab a used torsen with gears on ebay and plop it in my rear end housing.-Mike

Sonix

You've got it right, the housing is just what everything goes into. The pumpkin, the shell, two tube sticking out make it a rear end.

The carrier is what you bolt the ring gear to, the center section, contains the posi unit.