I saw a thread on here a while back where someone said their 9 bolt was worn out. I stared at the pics for a long time and couldn't find a problem.

I've got some RTV and some fresh gear oil and I was going to put this thing back together this weekend, but I wanted to ask yall first if you see anything wrong with this picture.



I'm just gonna wire brush the thing and put it back under the car. I'm a LITTLE worried that I might wind up with too much power for it (shooting for 400whp) but I wont be doing burnouts with it or drag racing, it'll be a driver car.





Thanks yall.

 

Your picture doesn't show the windows in the differential where you check to see if the cones are bottomed out in the case.

 

I mean, there's only a few tiny holes in that thing. What am I looking for here? I can't even get good pics of them because they're so small and partially buried by the ring gear.

 

Here's the only holes in it..

 

The hole in the first picture shows the cone inside the case. There are holes on the other side of the ring gear that show the cone on that side. This allows you to see if the cones have bottomed out in the holes. When the cones bottom out then the differential no longer locks up.

 

This?

I don't even...

 

Yes, that's it. It's hard to tell in the picture, but it looks like there might be a little life left in that one. I can't tell if the cone has bottomed out or not. Maybe someone else can see it better than me. You might have to get better pictures of those windows.

 

It's bottomed out, here's a reworked one with plenty of clearance (machined down cones and shimmed out)

 

Figures..

So I dont wanna spend $2k on a new rearend for this junker right now.

Can I just put the thing back under it and not worry about it for now? Or will it have problems?

 

You will not have posi, that's it

 

You can have it reconditioned. It requires a little bit of machine work, but it restores the correct operation of the unit. I think there is a sticky on here somewhere that tells how to do this. I've done a few myself.

 

Well frankly my power goals are ~400 whp out of this project, and I've been worried this rearend would not hold up to that in the first place, but I was hoping to just run it during the "restoration" and when I get it on the road, then replace it down the road if it starts to whine or give me trouble.

I dont think these 9 bolts are all that strong. I know the 4th gen 10 bolts are basically useless.

Hawks has an 8.8 bolt in but its like $2k and I just didn't want to pay that for something thats gonna sit for several years unused under this car.

 

There's nothing broken, just worn out. That doesn't mean it's weak. You can have it back in working order in no time.

 

From what I've learnt about the 9-Bolts, when they wear out (when the cones are worn out) they DO get weaker because the spider gears doesn't mesh correctly with the side gears.

As the cones move out from the center towards the sides, the side gears also move out. When the side gears move away farther from the spider gears, the gear teeth has less contact area.

Therefore they are substantially weaker when worn out since they are more prone to breaking teeth on the gears when they are under load.

 

From what I understand rebuilding one of these is very cost prohibitive as parts are nearly impossible to find and costly when you do find them.

I dont want to deal with an aftermarket diff, however, as I've been reading a lot into the other options, and they talk about needing brakes from other cars, and I really dont want to have to do that. (I want this project to be simple.)

If I can't get a solution for the diff the project is dead in the water really. I want to run factory rims on this car.

 

Some machining (hell even a flap disc works) and some 10 bolt pinion shims is all it takes. And yes poorly meching spider gears are weaker, that's why you shim it back up.

 

Reconditioning it isn't that hard. I've done several of them in my lathe and it's no big deal. It takes longer to sort out the correct shim thickness than anything else.

 

Would a shop in the Atlanta area know how to do this?

I don't have a lathe and obviously from my posts here, dont know a heck of a lot about diffs.

 

There is a thread on here somewhere that tells how to do this. Someone might be able to post a link to it. If you read it then you will understand what needs to be done. It's just some simple lathe work and shimming.

 

A flapper disc on a grinder will work also, just remove the raised lip from the small end of the cones and try to get it as flat as possible. With a die grinder remove the lip from the case or dress it down (optional but will give more clearance before it bottoms out against that) and then get some 10 bolt shims and shim the assembly on a bench so the spider gears are somewhat tight or with just a hair of backlash after clamping the spider cross against the case half (with a bit c clamp or something), do this on both sides (may require different shim stacks) and then after assembling with the axles in to align, put one axle in a large vise, insert the other and with a breaker bar try to feel for break away torque. It should have some good amount resistance but not stupid tight. There's no real rule of thumb, I do it by feel and shim tighter for auto x applications and looser for service on a driver.

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

https://www.thirdgen.org/forums/tran...r-off-9-a.html

 

Have you read my thread about my aftermarket diff install?

https://www.thirdgen.org/forums/tran...installed.html

I didn't need to replace any brake parts, I still have my factory rims and i got rid of the horrible cone diff once and for all. Basically the only thing I replaced was the diff bearings, differential and spacers. Very low cost. I did a real lazy n00b install myself though, no gear marking compound, no removing pinion or anything, I just checked the backlash and set the same for the new diff.

If it looks interesting, just email the company who sells the diff and ask them how much hp/tq it's rated for because that I don't know.

 

How much is that thing? I have seen the thread and been wondering, I'd love to have a torque sensing (torsen or helical) diff.

 

It's in the thread,

I ordered the diff for 495 Australian Dollars (approx 367 USD) + shipping. The total amount charged was about 527 US Dollars.

That shipping cost (~160 USD) was from Australia to Sweden, it might be cheaper to ship to the US.

 

I'm in the Netherlands, similar pricing (taxes over price +shipping and a nice import dujty over the total)

 

I dont think I want to be grinding the pinion gear down with an angle grinder.

I'd be happy just "fixing" the diff. I don't plan to be a tire burner with this car (although added traction is nice to have) but I dont want the thing bombing on me when I go to pass someone on the interstate or gas it through a turn or take off hard from a redlight.

 

The clearancing on the pinion is in a non-strength area and a non issue as far as that goes..

 

Yep, and I imagine I removed about 1 mm of material so it really doesn't matter at all. Of course you could remove the pinion and put it in a lathe, but then you have to do a proper full setup of the pinion and ring gear with new bearings, shims, crush sleeve and marking compound to check the pattern.

 

That's exactly how I reasoned when I took my stock cone diff out, replaced the cones, machined the housings and shimmed it tight again.

And indeed it worked perfectly!

...for 2 weeks. Then the cones were bottomed out again, and they were brand new cones from 9bolt.com.

 

How did you grind it without getting metal shavings all inside the housing? Even if you clean the mess out of it, seems like you might miss some?

I dont know that I even have an angle grinder small enough to make contact. (although, the pinion gear does rotate... so I really only need 1 angle.)

 

Just so you know....the way the factory 9 bolt works there are metal shavings being put into the oil all the time. Its not really a great design for longevity.

 

I wrapped a cotton cloth/rag around the front end of the pinion gear so that no shavings could get in behind it, then I just cleaned the housing out with brake cleaner and rags after I was done grinding. I used a pretty average sized angle grinder and rotated the pinion tooth by tooth to gain clearance.

And like subroc said, the terrible design of a cone diff which uses metal on metal wear areas does fill the oil with lots of metal shavings. So if you are concerned with getting metal flakes mixed in with the gear oil you should really get rid of the cone diff.

 

I always put a magnet on the inside of the cover when I build a rear end. I use 2 part epoxy to stick it to the lower part of the cover so that it can catch some of the metal in the oil. I would highly recommend this in any rear end, and especially one with a Borg Warner or Auburn differential.

 

That is a very good practice! There should have been a magnet in it from the factory IMO! I should've done this when I replaced my cones, would have spared me the hassle of cleaning the housing from all the grey metal-flake-goo when swapping diffs :S

 

TBH, I thought they had been doing that since the 60s.. but that may be transmission pans I'm thinking of.

I thought it was odd when I took the cover off of this one and didn't see a magnet.

 

As far as I know GM put a magnet on the inside of the cover of most G80 equipped rear ends starting with the 8.5 rear ends. I have never seen a 12 bolt or 8.2 10 bolt with the magnet.

 

I have 5 9 bolts and did some for others and have never seen a magnet.

 

If you want to get away from that rear,I'll work a trade with you. I have a 10 bolt 3.23 open with drum brakes, I live about an hour south of Atlanta or I could meet in Carrollton or Newnan.

 

LOL like anyone would do that

 

actually I've been considering finding another 9 bolt to roll on and keeping this one out and rebuilding it later

or.. just risking it and putting it in as is and hoping it doesn't die within the first 30 minutes of a running engine.

 

OK, tell me this real quick, if I get just any old 9 bolt, most of them are gonna have drums yes?

What would I need from this one to make it disc compatible?

I'm gonna try to see if I can get one out of a yard, strip it down, blast it, paint it, then rebuild it with new bearings shims carrier etc. I can roll on the one I have and then cut the backing plates over at the last minute if thtas all I need. That way this wont slow my project down, but wont blow up in my face later either.

that is providing the yard lets me get the rearend and they get the car out of the axle deep mud its in.. The years cheaper if you do the work but.. come on..

 

I haven't seen a 9 bolt with drum brakes. All of them that I have seen had disc brakes.