Well, I finally decided to go for broke and begin my quest for better acceleration on the cheap. My Goal is to complete the project as a bolt-in unit with the drum brakes. I don't have money to search for the LS1 brake parts or else I'd to the entire swap to LS1 discs as well.

"Egads!" you gasp. "Surely this can not be done!!"

Well, I seem to be doing it quite well. Here's what I've got so far:

2002 Firehawk Rear housing containg a 3.42 gear set and Posi, minus it's brakes and shields, etc.
Cost: My labor of installing a Moser 12 bolt in it's place for the previous owner of this 12,000 mile piece.

1987 Chevy Camaro V6 3.42 open Diff rear end. Bought it at a place in New Ringgold PA where $10 to get in and whatever you can drag accross the lines you keep. There wasn't much left on the car, but I did see the RPO Code sticker, and found the telltale GU6. Since I also got a reservoir tank, it cost me $5. ($10 admission/2 parts = $5).

Step 1 is to determine what budget I should work with. A quick search netted me on www.car-part.com for a used posi 3.42 rear was between $650 and $300. There were Posi 2.73's for less, but it's not what I want. I think $200 is probably overkill, but I believe I can put together a nice used unit with new brakes, etc. for less than an "as-is" Posi Unit.

Step 2 was to clean up the cores and see what I had to work with. Pics soon to follow.

 

Well, I found out that the axles are different between my 4th gen rear and my 3rd gen rear.

Now, I'm scratching my head as to what to do. I'd like to go disc rear brakes but money is tight. I have a good 3.42 open 3rd gen that needs brake work, and I'd like to slip a posi unit in it, but I don't want to put big money on a posi unit. Guess I'll have to find a posi unit from somewhere...

 

what year is the 2.8L rearend? if its an 89 or newer itl have the 28 spline axles, there for u can buy a SLP take out posi for 99 bucks and then have someone shim the carrier so the gears mesh right.

 

Unfortunately, it's an 87. Suppose I get axles from an 89 or newer and get an SLP carrier...

:edit: it's gotta be 90-up from what I've researched on this site. Back to www.car-part.com and I'm finding used axle shafts ain't so cheap. New from GM Parts Direct are about $129. Gonna Scour the local u-pull-me's for the right years. Anyone got a set of used ones??
:\edit:
I'm leaning toward that route and then swapping to the 4th gen once I've gotten the parts I need if that is feasible.

Any thoughts? I'd like to use this thread as a one-stop reference for a rear swap.

 

I am going to be doing a swap from a '91 10 bolt 2.73, drum and no posi rear to an '86 "australian 9 bolt" 9 bolt 3.27 disc and posi rearend, hopefully this weekend. The calipers and brakelines need replacing and I spent about 6 hours wirebrushing the old rust off... Should work out good when I am done. I hope.

 

I scored a set of axles out of a 1990 Firebird V6 at Harry's U-Pull-It in Pennsburg, PA. The Axles were $14 a piece plus $2 core charge. Guess where my 26 splines are going? You got it, free admission in the yard again!! Or if I wanted to get technical, when I return my cores and get my $4, the rear cost me $1.

Later tonight it's "get out the scrapers and paint" time and I'm going to begin the restoration process of this rear.

Here's what I've spent so far:
Brake Drums www.discountautoparts.com 14.98*2+$6.50 = $35.46
Rear out of 1987 V6 Camaro 3.42 Open Diff, $5.00
28 Spline Axles from 1990 Firebird V6, $14.00*2+$4 core =$32

total so far $72
More to follow!!

 

Ok, haven't had the time I would have liked to continue with the project, but here we go.

I decided to swap carriers only and not mess with trying to match up the gears from the 4th gen rear. Having that done, I decided to move on to other things, like:

Brakes: I began putting together a list of parts I'll need to put the brakes in order. After doing some searching, I found that I needed to keep my old lines from my 2.73 rear. I found this tidbit of info about wheel cylinders, since I need new ones and wasn't sure about the fittings on the 86 and 87 lines.

"Your '86 Z28 should have metric fittings... all 84-up f-bodies have them...." -Tom P.

so, I've got 2 wheel cylinders to order with metric fittings, brake hardware and shoes to look for.

I'm also looking at axle seals, axle bearings and a pinion seal. If anyone has a number for the pinion seal, please let me know.

 

Ok, gotta see if I can find the RPO sticker for my car. The previous owners spilled something in the console, and it peeled off. I put contact paper over it and stuck it in my Haynes manual, which is at my parents place... I'm 90% I have the 7.625 gear on the Bird, because the bigger gear is the Borg Warner 9 bolt... no?

I wish I'd taken the RPO sticker off the camaro I got the rear from... damn... I'm pretty sure the car is long gone now. Anyone able to confirm or deny these somewhat conflicting comments?

 

Finally another day to do some more work on the rear. I found an absolutely amazing primer at K-Mart Krylon Galvanizing primer with a fire hydrant on it. This stuff goes on thick and makes a really nice basecoat to which I'm applying Wal-Mart's brand of rust-oleum gloss black paint.

I also touched up the axle ends and drum backing plates. I'm planning on posting photos of the assembly process on sunday

 

I am not for sure but I thought I was told buy the guys at Moser or Richmond that the 7.5 and 7.625 ring gears are interchangeable and that they are the 10 bolt only?

Anyone who knows more about this that me can step in and let me know too. I have always wondered what the dif was.

 

i believe they are the same size, just GM changed where they measured the gears from. they're all 7.5inch rear ends, or you could call them 7.625....it's all the same exact thing.

 

This is what I thought because I had no problems when I built my 10 bolt. I asked a lot of questions, I think I asked about the 7.5 and 7.625 to about 3 different venders and got the same answer.

 

Wonder if that's got something to do with the whole switch from inch to metric thing of the mid-80's...

...then again maybe not because neither comes to an even metric measurement... The housing gaskets between the two sizes ARE different. I brought my cover over to NAPA just to be sure.

 

So I'm not quite understanding your dilemna here...

You have the LS1 rear end, but it doesn't have discs, calipers and lines on it?

 

that's correct, and rather than spend $800 on used parts, I'm going to use the posi diffy in a 3rd gen housing until the LS1 rear brake parts hit the aftermarket.

The spare 3rd gen housing was $10 and the 4th gen housing minus brakes, etc was free, so I'm showing a cost-effective alternative for a Posi rear for cars making 350 horses or less on street tires.

 

unfortunately My digital camera is dead.
Here is a list of parts and prices:

To recap:
1.) I got the housing with 3.42 from a u-pull-it yard for $10. I cleaned it up and repainted it for another $15 between brakleen and paints.

2.) I replaced axle bearings and seals for $34.00 and wheel cylinders for $11.49 each. Napa application engineered brake shoes for $32.49

3.) Rubber brake hose from Auto Zone for $10, Maxi-pack of new springs and hardware$11.50. $35 for new parking brake adjuster kits through Napa.

4.) New Brake Drums $35.46, Used Axles $32 Used SLP Posi (free for me)

5.) Pennzoil Synthetic 75W90 $14 for 2 quarts. Diffy Gasket $5 Pinion Seal $7 New Gabriel VST shocks $40.

Total cost came to about $300. Add $100 if you need to purchase the SLP posi.

I went all out on the new brake components, only because in my opinion, brakes are something you don't skimp on. I felt my main bearings and pinion bearing were in excellent condition. Replacement of these is a signifigant cost I don't have listed. I could have reused all my old hardware, and opted for cheap new brake shoes to save a bunch of money, but I deciced again that brakes are something not to skimp on. I did reuse my hard lines off my old 2.73 because they were in excellent shape.

Let me just say the difference from a 2.73 to 3.42 is AMAZING. My lil 305 needs much less pedal to get it moving, I'm definitely looking forward to better mileage on this stipulation alone. If this is something you are considering doing, by all means, go for it.

Get a complete housing, preferably from a 90-92 v6 car. I know of 5 such rears in my area for about $35 in the u-pull-it yards here in PA. That should save you some money because the correct axles are already there. DON'T SKIMP ON BRAKES. go with the best ones you can get with new wheel cylinders and hardware. Replace the shocks if you are still running your stock ones. This really was a pretty straight-forward project, and the yards are brimming with v6 cars.

Also, your speedometer will be signifigantly wrong... you will be reading about 15% or so faster than you actually are. Get the gray and yellow speedometer gears... I believe they are the closest (for an automatic)

 

That's not too bad I guess.
I bought my complete 99 SS rear end with brakes, LCA relocation brackets, and 4.10 gears for $150 + a rear with axles to go back on the car before it went to the scrapyard. I had to stick a rear on the 99 so it could still roll.

 

nope, it wasn't bad at all. For the way the ting drives now, I can't believe I hadn't done it sooner.

 

Sounds like I got the best deal yet. I found a guy that had a 98 Z28 stripped to the ground, but still had the rear from caliper to caliper. I built him a computer and after it was all said and done, I profited about $5 and the whole rear from caliper to caliper. I've been putting it in this weekend. Halfway done and the only problems so far are the difference in brake lines and parking break lines.

By the way, after I got this deal, I checked them out on eBay to see what they are going for. 2 of them sold that week for about $250, also from caliper to caliper.

You guys want to see pics of the 2 rears before I put the new one in. If so, I'll need to know soon. I have to borrow a digital camera from my neighbor, again. My 2 year old got to mine, lol.