I'm trying to figure out the cheapest way I can get limited slip in my 86 camaro. I just dumped a lot of the money I have budgeted to put into car improvements right now on suspension upgrades. But I still really need to get some form of limited slip. It doesn't have to be a pretty solution for now, just something that will work until I can find / afford a better rear end.

My rear end is a 10 bolt, I'm not sure on the gear ratio atm as I haven't checked that yet but I'd be will to bet it's a series 2 carrier as I don't think it's a very big ratio. Based on what I have read it should be 26 spline axles.

I've got another camaro that has a 97 trans am rear end in it with drum brakes. I haven't inspected this one much yet, but I assume it's a 10 bolt as well, not sure if it has posi or not either (did they come in 97 without posi?)

Anyway, I know I can't simply swap the gears from the 97 rear to mine if it has posi due to the axle spline differences, and I can't swap the axles due the 4th gens being longer. I can't really do a complete rear end swap either because then my 87 Iroc wheels won't fit properly.

Would it be cheaper to try and find someone to shorten the 97 rear end (assuming it has posi), or any suggestions on what my options are for the cheapest method to get posi in my car for now? If I could find a rear end locally with posi in it for a good price I'd go ahead and buy it but I haven't been able to find any locally. Well besides hawks that wants a ridiculous 500 dollars for a 10 bolt out of an 84.... If it was out of a 90 - 92 with the 28 spline axles I might would consider paying 500 dollars for it even though I know that is still a bit high, but out of an 84 with the smaller 10" disc brakes and only 26 spline axles that is about twice as much as I think it's worth.

 

Best solution is probably to find some stock 90-92 Axles and move your fourth gen posi over to your 3rd gen.

 

the 4th gen should be posi, im not sure how it was for the firebirds but i know z28s came with posi and i had an option on my old v6 98 that made it a z28 all except for the engine and it had positraction.... kinda miss that car now

 

Just to confirm something with this. I was under the impression that all 90 and up 10 bolts were 28 splines. So I assumed based on that, that the ones in the 4th gen rear end I have were 28 spline as well.

I just called a local Camaro parts place, and they said that some of the 4th gens where 26 spline and some were 31 spline. Is this accurate? I mean I can try to pull one of the axles out of the 4th gen to count it to verify later this week but just seeing if anyone here could clear that up prior to.

I should be able to get a set of 90 to 92 axles fairly cheap too. I was just out at my local pull a part the other day looking to see if they happened to have any 9 bolts and I'm pretty sure two of the cars I looked under were 91s and they still had the axles with 10 bolt rear ends. They are only 20 dollars each according to their price list, so as long as the 4th gen rear is 28 spline and has posi, I might just do that.

Is there any other costs associate with doing a swap like this that I should be aware of? I'm guessing I should put new bearings on while doing this, anything in the gear box itself that I should replace?

 

Well actually, even though this would be the cheapest route (if I knew how to do it), it might be beyond my skill lol. Just read a couple posts on how to change out the axles and how to install new gears and I don't think I could do it without some supervision =P

And by the time I pay someone to help or do it for me, my costs are right back up there, *sigh*

 

No. 28 splines. For more info, check the 10-Bolt FAQ at the top of the page.

JamesC

 

Its not as hard as it sounds, but I dont blame you for being intimidated. It's better if you have another daily driver.

However, just a quick word of encouragement. Your gears in your 3rd gen and the gears in your 4th gen axle interchange (If they're both 3-series or 2-series anyway, meaning both 3.08 or numerically higher ratios for 3 series, or both lower than that for 2-series) - so if you screw up one set of gears with a bad setup, you can just use the other. And if you screw up a second with a bad setup... guess what.... used gears are $50-$75. They may or may not whine from being used and abused, but by the third time you will be getting pretty good at doing it! Remember, whats the worst that can happen? You'll wear some gears funny and have to buy another set at $50 and do it again. REALLY not that big of a deal.

I had a buddy walk me through it and help me with the work, but I think I could do it next time relatively easily.

The tools you need officially are different form the tools you can get away with. The only thing that may cause a problem is getting the pinion bearing pressed on. You can go have a shop do that fairly cheaply I imagine, it's not difficult. You can go buy a $125 harbor freight press and do it yourself if you want, but it's not a huge deal.

Here's what you will need to do it:

1. 2 qts Gear oil (you may even be able to recycle the old stuff if you like)
2. Shim kit for a 10 bolt posi.
3. If you take it apart and find any bad bearings, you will need to replace them. Have that done when you do the pinion bearing.
4. Your new 28 spline axles
5. Your 4th gen posi
6. Solid Pinion spacer (ratech is good for that stuff, they're cheap and greatly simplify the assembly process)
7. Permatex prussian blue marking compound
8. Carrier shim kit (get this from ratech too, I like them a lot)

And here's the tools you'll need from what I remember:
1. BFH and crowbar
2. Heavy Duty electric impact wrench (and obviously impact sockets) - we rented it from an auto parts store
3. Micrometer/caliper to measure shim thickness
4. Dial indicator with magnetic base. I used this one from summit. It worked just fine.

Read all the websites that tell you how to do it a few times, and then read the quick shortcuts Im about to give you.

1. First of all, save yourself the irritation, and just pull both axles out of the car and put them on jackstands where you can work with them much easier. Doing it the hard way will make it easier in the end. Just pull that sucker out. My buddy showed me a trick with a couple of vice grips on the brake line to keep it from leaking fluid all over the place. Even if that damaged the line (which it didnt), I could replace it and just gravity bleed it a little bit and it would be fine, vs having to deal with a completely drained master cylinder.

2. If your other two rear ends are assembled, feel how easy it is to turn the pinion gear (via the driveshaft u-joint block) with the axles and carrier removed. All those sites say to use an inch lb torque wrench to measure pinion gear preload... you have two axles to feel the factory preload on first hand for a reference. It's not an exact science, and the world wont fall apart if you're a little off. So if you cant get an inch lb torque wrench, dont worry about it.

3. Each carrier will have its own shims and so will each pinion. If you're moving the 4th gen stuff into the 3rd gen axle, i would probably use the thirdgen housing a reference point. Use the shims it came with. Just keep all your shims set aside and labeled, you can always swap around and see what works. If the pattern looks awful with the shims from that housing and a few adjustments dont seem to help, switch to the other axle's shims.

4. pinion bearing preload... When they say to torque down 250 ft lbs on that nut to compress the crush sleeve or crush collar, that automatically sets the preload correctly but you have to put 250 ft lbs on it to do it. Screw that, Im not gonna mess around with that garbage. Take your old crush sleeve that comes out, use your micrometer, and measure it. You replace the crush sleeve with a solid pinion spacer. It will come with shims. match it to the old crush sleeve. Voila, no more having to hoss down 250 ft lbs to start reading your patterns. Greatly simplifies the logistical issues with putting it together. Then you throw it in and you can feel your preload as I mentioned earlier. The inch lb torque wrench can be gone without, just try to get it close to how it felt before. As long as it's not loose or super tight, it'll be fine. if you measure the crush sleeve that comes out and match that, it should be right on the money, maybe some small adjustments here and there but nothing major. If it it feels all wrong, measure the OTHER crush sleeve from the other differential and match that one. See which works better. It's not hard I promise. Note you do have to torque down the U-joint yoke to .... real tight (not 250 lb ft like before, but you know...) to measure this. Use the electric impact wrench.

The first 4 points were just addressing concerns I had about "Man do I even have the tools/ability to do this stuff?!". With that out of the way you should be aware that you CAN do it without all that much trouble. From here on is the precision work part of it that is the other element of intimidation.

5. At the end of the day, all you're trying to do is get a good pattern with the correct backlash. Use the factory carrier shims, measure them, throw them back in place, install the carrier and bolt it in, then put the purssian blue all over 3 of the gear teeth (both sides of each tooth) on the carrier gear, and rotate it through and watch the pattern. Do a google search for gear patterns and you'll see a lot of examples. If the carrier flops around, you need thicker/more shims. If the carrier can barely turn, you need to remove shims. Just measure what you have, and use your shim kit to adjust thickness. If the pattern looks bad, check backlash... If the pattern looks good... check backlash.

6. Backlash is the slop between the gears. Hold the pinion gear in place and turn the carrier til it hits, then turn it the other way til it hits. It's a bit tricky, and again, not as exact of a science as you would expect. Put the magnetic base on the housing and set up your dial indicator as best you can against a carrier gear, push it until rests against a tooth on the pinion gear and zero out the indicator. Hold the pinion gear, and rotate the carrier the other direction until it hits the other tooth. This slop between teeth, is waht you're measuring, and it's a little tricky, but you do it a few times and watch what the gauge tells you. Use common sense. If you rock the gear 5 times and it shows .015, .016, .015, .049, .018, it's probably around .016 or so.

What you want is to have a good pattern with the correct backlash (.008-.012 I think is the correct range, tighter backlash is stronger in theory and will be less likely to grenade the gears on a hard launch). If the backlash is too tight, use shims to move the ring gear away from the pinion gear. Move the carrier the opposite direction. If you've got too much slop, move the carrier towards the pinion gear. Getting the backlash right will get your pattern looking nicer. It will all start to come together pretty quickly. All you need is good pattern with good backlash. Then you are DONE. Just fill it with the stink fluid, seal it up, put the axles back in it, mount it back in the car and have a good time.

 

I would just go the junk yard and buy a 4th gen posi rear for like $150

 

If I was going to do that I would just use the 4th gen rear I already have. But I want my 87 Iroc wheels to fit properly. On a 4th gen rear they would poke out and look really stupid =p

Thanks Infernal for the tips. I may still end up trying this, I don't know yet.

I found a 9 bolt 3.08 posi with disc brakes nearby to me today and am considering just buying it instead. It's more than I want to spend right now at 350 dollars, but ultimately I think with the lessened headache of trying to figure out how to do the gear swap, it having the bolt in axles that I wanted to get eventually anyway, plus switching to disc brakes on the rear, I might end up getting it. I know I'd have to do a proportion valve and possibly run new brake lines / ebrake cables for the hub to disc swap, but I can't imagine that being as hard to do as the gear swap haha.