So i finally got a rear for my 86. A friend of a friend was selling it from a totaled Camaro. Paid 300 bucks, its a 3.73 Posi, disk brakes.



Pulled the cover and the gears look perfect. Fluid was pretty nasty.




So what brand and viscosity of gear oil do i need to use? The stuff that came out was really thick, like syrup.

 

You can go to Walmart or any auto parts store and buy 80-90 gear oil. I would be on the safe side and add some posi additive too.

 

Its gonna take about 1+ 1/2 bottles of 80-90 gear oil.

 

So i just fill it up until it comes out of the fill hole right?

 

exactly

 

if its acutally a LSD, then use dino oil and the moddifer

synthetic oil is normaly to "slick" for a LSD

 

I'd suggest you check the ratio carefully....

That looks like a 9-bolt, and 3.73 wasn't a stock ratio in them. Was available aftermarket but there are VERY few in existence.

But more important: I see a HUGE pinion, looks like MUCH larger than 1 / 3.73 times the dia of the ring. It looks 2 series to me. And, I see 6 pinion teeth in MUCH less than half of its circumference, meaning that there are AT LEAST 12and probably alot more than that; but 3.73 is 11 and 41. Meaning, NO WAY IN HADES that's a 3.73.

I suggest you COUNT THE TEETH before getting all excited.

 

It also 'appears' to have the 9-bolt rubber fill plug on the diff cover.

JamesC

 

Dammit your right, it's not a 3.73. 13 pinion teeth, 36 ring. It's a crappy 2.7

 

Called him and left message, well see how it goes.

 

well,i would try to sell it and if you have trouble at least the rear is out of the car and may be able to do a ring and pinion swap easier now. its just a matter of finding gears.

 

lol, anyone who is interested. 100 bucks off what i paid.

https://post.craigslist.org/manage/2806145554/knn5j

 

oh well, 2.77 would be good for turbo

 

I found a 3.27 out of a 1988 camaro near me. Same posi, disk. Not sure if its a 9 or 10 bolt. If it is a 9 bolt, i can swap in the 3.70 gears because it has a 3 series carrier, right?

 

thats a 9 bolt,yes. Is your 86 an auto or stick? what ratio is in it now? cause 327 is not a bad ratio.

 

It was an auto with an open 2.77 drum. I'm putting in a t56 from a 95-97 LT1

 

I called up about the 3.27 and it's 250.00 and a 9 bolt. I'm gonna go down there tomorrow and pick it up. As for the "3.73" the kid already gave my money to someone he owed, so I'm not getting back squat. I want to do small claims but I'm not sure if I have a case. There are no recipts but I can get the phone records showing I talked to him. I'm thinking if I can call him and get him talking about the rear on tape, then I will have something.

 

The limited slip on 9-bolts often are shot (a search would tell you more). Perhaps you should familiarize yourself with as much info as possible before dropping more coin.

https://www.thirdgen.org/forums/faq-...now-about.html

JamesC

 

I'm gonna rebuild the rear before it goes in anyway. Either gonna keep the 3.27 or upgrade to the 3.70. I would do the same with the 2.77 if it would support 3 series gears.

 

The original question was about the oil to use. I just got a 3.27 (definite) 9 bolt posi and started reading up on it. There seems to be no agreement on the oil. Synthetic or not. Additive or not. Red Line. Can anyone give a definitive answer? What did GM say?

 

did u buy it yet? are u dead set on a posi? cause u can always get a used 10 bolt from a v6 car(same car) and have a 342 or 323 gear ratio. They are like $100-150 at a junk yard.

 

Yes. I got an '86 TA (no engine/trans) for the rear (9 bolt 3.27 posi disc) to replace my 3.23 drum open diff. $300 for the car and I'll sell the rest if I can so seemed like a good deal. I'll clean it up rebuild calipers etc. before installing it but I saw this thread as well as all the 'old' threads and wondered if there was ever a resolution about the oil/additive argument.

 

I would definitely NOT use posi additive on 9-bolts. I dont with mine.

Also I would seriously reconsider getting a 9-bolt.

They ARE stronger than 10-bolts. But they arent super strong, being stronger than a 10-bolt aint saying much.

Ive gone the 9-bolt route, adn I got mine because that's just what I could find at the time and it had the 89-92 rear disc brakes on it.

If I had to do it over again I'd probably take a pass on it.

I've got $200 in gears in it. Worn out posi cones that need to be replaced, another $150. Plus the hassle of all the work involved to put the gears into it, the gear oil, and the bearings and seals that I had to replace when it came apart... with original purchase cost, and all the money I've had to spend on it iwth the addition of the posi cones it needs and will hopefully get soon, it will be getting to that $750 range.

If I had to do it over again I'd get a 10-bolt. They're like legos. parts everywhere, you break one and there's another one you can get and swap it in and move on with your life. With a 10-bolt, you just get one with a 3-series posi carrier and you can get some used GM gears for $50-$75. You blow up the rear? Who cares, just buy some new gears and slap it back together. The posi wears out or is damaged? Who cares, you find a new one and swap it in. The key is that the options are there. The gears are everywhere, the posis are everywhere. You will need to practice your gear setups if you plan on abusing them, but you can probably blow up 5 cheap 10-bolts with cheap 10-bolt parts for the price of one 9-bolt with good gears and a good posi... and the 9-bolt may break just as easily as the 10-bolt depending on how much power you're making.

So are they better? technically they're a lot better. But for us, I dont think it matters. The cost difference is absurd. You'll spend 4 times as much on new aftermarket 9-bolt gears as you will on used 10-bolt gears you can find anywhere.

 

OK no additive. What gear oil do you use? I've read all the pros/cons about the 9 bolt swap and I looked for a 10 bolt locally and every I found had been stripped. If I manage to sell a bunch of parts I hope the rear will be almost no total cost. Plus I'm going from drum/open diff to disc/posi. The car is used mainly for auto-x and some local driving. Also, I'm running the 3.1 so I won't be straining anything. I read that one test is to lock one wheel and measure the torque required to turn the other. If less than 35 ft/lbs it needed rebuilt. The one I've got took 55 ft/lbs to move. How good is that compared to a fresh one?

 

With the 9-bolts Im not really sure how accurate that torque to rotate the wheel test really is. My cones are visibly worn out (you can see in the little windows on the posi carrier) but my posi still works beautifully right now. I ran synthetic for a while, ran dino for a while. Since I put in the new gears I'm running synthetic to help the gears break in properly.

Unfortunately when the cones bottom out from wear it can cause the spider gears inside the differential to grenade... and at that point you may as well just trash the rear end. The carrier at least. New cones are around $150-$200, which isnt awful bad, but it just sucks how limited you are in sources for them and there are truly NO other options out there for a posi carrier other than the stock one. There are tons of options for 10-bolt posis. Even if you blow one up you can go get one from a junkyard or you can buy a new one of any sort you can imagine - lockers, torsens, clutch... all available. 9-bolts aren't quite so easy to source parts for. They ARE available, but you just have very limited options. THe only aftermarket gear available is 3.70's as far as I can tell. All other ratios are factory ratios in this or that car or gears sourced from australia where these axles are FAR more common.

 

9bolt.com sells 4.11 gear sets. That's the ratio I would like use because I'm going with a t56, and it's going to be a city car. As far as axle bearings, I can't find a sight that sells them. Are they the same as 10 bolt as bearings or are they completely different?

Btw I picked up the 3.27 and I'm gonna start taking it apart soon.

 

Have you ever set up a ring and pinion before? You know that you can buy a solid pinion spacer instead of a crush sleeve,just incase you don't get it right the first time and it is re-usable.

 

thats cool , and you can even sell the 3.27 gears now to someone, cause they are a decent gear, especially for a 700r4 auto

 

Ok I snapped two of the pinion bolts trying to remove them. Now what?

 

Correction, the ring gear bolts. Can I use the half out of the 2.77 or do I need to use the 3.27 one?

 

dont sweat it. Your new installation kit should include new ring gear bolts, shims, pinion nut, crush sleeve (although you should use a solid spacer), and gaskets and marking compound.

 

remember the ring gear bolts are loosened by turning clockwise as if you were tightening.

 

If you have never done this before you should watch some youtube videos, take your time and do your homework man.

 

Righty tighty, lefty losey doesnt work on those. its righty loosey lefty tighty.

you better get a factory Helm GM service manual B4 you get in over your head..

I have built well more than 300 rearends and its not hard but if you have never done it please do some research b4 you dig in!

 

I noticed the L on the bolt after I broke 2 . The good thing is I got it apart and I'm putting in either a 3.70 or 4.11 ring and pinion so the broken bolts in the ring don't matter. There is a good amount of wear on the cones and case so the cones will need to be replaced. I may just weld the cones in and not replace them for a nice 100 percent lock.

My friend has that done to his super and I like it. everytime he turns you just hear chirp, chirp, chirp.

 

whats really important is to get the pattern right. you need to use marking compound and look at the pattern it creates when you turn the gears. you can mess up your gears if u dont do this right. also after u get the pinion off u need to get the bearing removed with a press or have a shop remove it. i suggest you keep your stock shim(.35) that is on it and be careful not to damage it.

 

http://www.youtube.com/watch?v=Zgl5xcZmWpI

that video may prove useful to u.

 

http://www.youtube.com/watch?v=N_6VpBWVcZs

video of getting pattern correct

 

youll' be happy tho after u get it done. best thing i ever did to my car. picked up over 3 tenths of a second

 

http://www.youtube.com/watch?v=8APYO...eature=related

when you get everything installed u will need to set bearing preload,this may be useful for u too

 

its not that hard if u take your time and watch some videos

 

Is yours fully locked? Also I meant to say "Supra" before. His car is a daily driver family car too.

 

no way, locked is no good for the street. mine is a 342 non-posi,out of a v6 car

 

I'm gonna go with the 4.11's due to the fact that it's mostly a city car and because I'm going with the t56. Gonna order new cones and a bearing kit with all new shims and seals. Just have to get a dial indicator to set the backlash when it comes time.

Where can I get 9 bolt axle bearings? Mine are pretty cruddy and need replacing. All the rebuild kits I find only include the carrier and pinion bearings.

 

Now that i have a 3 series carrier from the 3.27 i just bought, could i put that carrier in the 2.77 axle housing? The axle bearings and races are in much better condition than the 3.27.

 

Housing should be the same.

 

What exactly is the difference between a 2 series and 3 series carrier? I took the 2.77 carrier out of the axle. I looked it over and everything looks identical to the 3 series carrier. What am i missing? Also both carriers have a 36 tooth ring gear. The only difference is the 2.77 has a 13 tooth pinion and the 3.27 has an 11 tooth pinion.

 

man,that would be sweet for the disk breaks alone

 

Ahh. I did some googling and now i see that the flange where the pinion bolts up is longer on the 2 series carrier. Is this the only difference in carri

 

For some reason the page refreshed and the post went up before I finished typing. Anyway, is that extended flange the only difference between the two carriers? The reason I ask is because the other half of the 2 series carrier is in better condition where the cone sits. I'd rather use that one of possible.