I have no problem eating crow -- I probably jinxed myself even mentioning that my 8.2" was holding up OK the other day. Either that or you got your 68 Camaro Voodoo doll out, sprayed it red, and started sticking needles into the rear end . . . j/k

Seriously though, I guess it's time for me to do something . . . I was hoping you could point me down the right track.

I just put in a new Eaton posi this winter and broke two teeth on the ring gear my first trip to the track yesterday. I noticed when I got it home that it was dripping oil from the pinion seal too. I hate to waste my brand new Eaton posi.

Should I fix the rear end or dump it?

Any ideas on how to do a "new" 8.5" or 12 bolt on-the-cheap?

Sorry to hear about that. I wish I had been wrong on this one. I priced a complete 8.5 Nova rear end with 30 spline axles and Eaton to another guy the other day for about $1250. You could try another set of gears. Maybe next time they would hold up better, but who knows. I'm sure the 8.2 Eaton would not be hard to sell if you decided to go with the 8.5.

I hope it wasn't my fault for even mentioning it. I think I will still go with the 8.2" for one reason 8.5's hard to find here for some unknown reason, and two, $1200 was a lil' too steep for my budget. I don't run slicks <yet> and it sees lil' track time.

Freddie, I've been researching how to setup a new set of gears to see if maybe I could find what went wrong with mine.

I think that I may not have preloaded the carrier bearings enough when I swapped in the Eaton. Do you think that insufficient carrier bearing preload could have caused my ring gear to fail?

I was thinking that backlash was already on the loose side. It measured .014" when I took the Auburn out -- I took backlash down to .011" when I put it back together, and the gear set had .008" engraved on it.

When I shimmed the new Eaton carrier I went after getting the right backlash but was still able to install and remove the carrier by hand. It wasn't loose -- it fit snugly, but could be installed and removed fairly easy by hand. From some old threads here, I got the impression that the carrier should fit tighter than that -- I gather that I should not be able to remove the carrier by hand. Do you agree that I should have added .007-.010" of shim to preload the carrier?

I was thinking that if backlash was already on the loose side and there wasn't enough pre-load, maybe under hard acceleration the "loose" carrier bearings could have allowed side deflection opening up backlash even more under load.

I'm thinking that I may give a new gear set a shot and that I might as well do it myself and learn how. I already got everything out of my case (carrier, axles, pinion gear) and I think I understand how it goes together. If I screw up again, I guess I'd only be out a couple hundred.

I thought seriously about having you build me a new 8.5" but I just can't swing the cash right now (got nailed with a big State tax bill) :rolleyes: I'd like to make this rear live for another season, so any suggestions you my have are welcome.

I don't know if the loose bearings would have caused your problem or not. The bearings should have been tighter, but the gear may have just been ready to break anyway. The backlash on new gears is suppose to be set at .008 +/- .002, but your backlash was more because of normal wear. I see used gears with .010 to .015 a lot. Try a new set of gears and take your time to get them set just right. It usually takes many trys to get the pinion depth and backlash just right so that the contact pattern is where it should be. You will be proud of yourself when you get it done.

Thanks for the help BGH --- I found some of your old posts and followed your instructions. My new 3.73 gears are in and it ran quiet on my test drive.

Backlash set at .008 added .007" of shims for carrier bearing preload, pinion preload set at 19 in/lbs (new Timken bearings). Reused the old pinion shim from the 3.55 set and the pattern matched up with the pic in Richmond's directions. Geez did it take some serious grunt to compress that new crush sleeve :eek:

Only one question . . . is the Royal Purple 75w90 synthetic OK for the Eaton posi? I hope so -- I took the counter guy's word for it and put it in.

OK, one more question -- I used the money I saved on gear setup to buy a HD cast aluminum cover with the bearing preload feature. Did I just buy an overpriced cool-looking cover or do they actually help durability?

Thanks again!

The Royal Purple should be all right. I don't know much about it, never used any. In my opinion the cover does help. It does 2 things, it supports the bearing caps and strengthens that huge hole in the back of the housing.

Eric,
I run one of those covers as well and everything I reseached said they really help. So far so good and I built my rear end a few years ago.

Did you happen to het studs to replace the carrier bearing bolts? I was told that really improves the strength as well. If I remember right I got ARP studs with my rear end cover.

Can you feel the difference with the 3.73's in there? I know you will notice a difference on the highway. You did go with 3.73's, correct?

Yes, I got 3.73s. Did not do studs though -- the local speed shop couldn't find any listing for the 8.2". I didn't think that was a big deal . . .

I haven't got on it with the new gears yet. Just a nice low speed cruise around town for an hour yesterday to break it in. Besides, I have my street tires on it now which makes it pretty useless for any WOT testing; if it just smoked 'em with the 3.55's I'm sure it will just smoke 'em with 3.73's. :D

I think I will have to recalibrate my speedometer though. I was driving 10 over to keep up with the old farts . . .

Originally posted by Eric68:
I haven't got on it with the new gears yet. Just a nice low speed cruise around town for an hour yesterday to break it in. Besides, I have my street tires on it now which makes it pretty useless for any WOT testing; if it just smoked 'em with the 3.55's I'm sure it will just smoke 'em with 3.73's. :D Freddie, now that Eric mentioned it, which is your recomended break-in?

I run it on jack stands for about 10 minutes in both directions to get the oil circulated well. Then I drive it easy for about 10 minutes while checking for noises and let it cool well. Then I recommend a 30 minute drive and let it cool. After that I recommend easy driving for a few days and then let it loose.

Allright, my turn.

Do you have any pictures of the ring and pinion after failure? Your failure analysis can be narrowed down pretty quick with a couple of pictures. But my bet is that impact loading is what peeled the teeth of the ring gear.

Secondly, the oil. I have pretty much used every available oil on and not on the market. This is to include some, that certain institutions wont even reconize that they exsist. 'Royal Purple' before its public release is an oil product that I have tested in differentials and in my opinion, depending on the specific application, I would not recommend using it in a differential that will be used in high impact loading situations to include low speed-high impact.

My recommendation is for a 140 straight weight, parafin based or a blended syn like what you would find from LE, Amsoil or Schaffers.

Next, until I can see some pictures, I dont think the carrier preload is something to really point a finger at......yet. I say this because the driverside carrier cap will normally fail if the carrier was that loose. But you are correct, there needs to be sufficient pre-load that would take the use of a 56oz dead blow hammer for it to be seated. On carrier bearings, I actually go a bit higher on than to that of what the pinion bearings would be....roughly around 35-40 lbs/in.

And for what it is worth, I wouldnt touch one of those 'pre-load' covers to save my life. I just happen to know the guy that designed that cover (and then sold the rights off quickly) and even he says that they dont work, because they actually work against each other. There are 5 different metals that are all expanding and contracting during operation and trying to guess at what the actual preload needs to be is hit and miss. Too loose and it was like it wasnt even there....too tight and it can pinch the bearing and create spawling and radial stryations which lead to bearing failure. You would be better off installing a billet carrier cap and or some ARP studs for the driverside carrier cap alone.

Now for the most important thing for a differential.....the break in. I normally do a test drive to check for the obvious, then I recommend that it be driven 15 or 20 miles and then let it cool down to ambient. Do this for about 5 to 6 cycles before you even think about 'getting on it'. As it works out for most, a drive to work in the am and a return trip in the pm can do the same thing.......as long as you dont sit in traffic and live like 2 minutes away from work.

Just some food for thought. But an 8.2 is only as strong as the pinion shaft diameter and it will knowingly fail at some time or another. Fix a diff two or three times and it ends up as being just as much if not more than swapping in something more worth while........

On the subject of break in, what do you all suggest for a race-only car where street driving is not possible. Will running the car with the wheels off the ground for a specific period of time be sufficent?

Thanks for the encouraging words Chicane . . . tongue.gif

I can't do any pictures because my digital camera died. The old ring gear broke 2/3 of two teeth off the outer edge of the ring gear (the inner edge of these teeth were completely intact). The teeth were cleanly broken off and found lying in the bottom of the case.

As for the oil and the support cover, its done now and I'll have to see how it works. With only $400 into my repair, I'm not expecting it to make this 8.2" last forever -- just long enough for me to get the cash, locate a good 8.5" 10 bolt core, and build it. I'd like to build a different rear end next winter -- so hopefully this one will get me through the summer -- shoot, it got me through three years until now.

Replacing the ring and pinion in this rear was an excellent learning experience -- I'll be sure not to repeat the mistakes I made this time with a new build.

Why do you say 35-40 in/lbs? Seems like that would generate a lot of heat. Why would you want that much preload on the pinion bearings anyway? There are numerous posts here and at Team Chevelle from different people that are recommending anywhere from 10-12 for used bearings and 18-25 for new bearings.

Any suggestions you may have for building an 8.2 or 8.5" would be welcome. I'm still learning . . .

PS. I just realized you were talking about carrier preload . . . how would you measure carrier preload? TQ wrench on an axle? With the pinion in place or not?

Eric The hardest thing for a guy to explain is how to set up a differential. I mean Freddy and I could probably throw numbers at a guy until he is blue, but it isnt going to tell him how to really do it.

Really though, setting up a differential can be a black science and it takes years of experience to get them down pat. I started out in the biz doing my 8.2 and then the second one....and then figured out how to make it live. But it was a lot of trial and error. This is really a touch and feel type of mechanics. I can tell you 25 rolling inch pounds on the pinion pre-load, but I can not tell you what it feels like. If you do it enough, you pretty much keep your arm calibrated.....so carrier pre-load has always been a feel thing for me. But you get the idea from how hard it was to install when using a 56oz dead blow hammer to install it......how much effort did it really take to hit the carrier into the housing.....

On to the nitty gritty. From what your explaination of where and how the tooth broke, it sure sounds like tooth deflection got the best of that gear set. To combat this, you gotta set up the gears with a "Performance" pattern, which means it needs to be set up deep on drive and centered on caost. The lash adjustment is tuned for the weight of oil that is going to be used (it gets this sensitive).

The thing about 8.2's, is that they can live a long life.....if you never hook it up. I have a good friend that has a 64 Duce with an 8.2 and a 700+ hp blown small block to include another 500+ hp in a ProShot Fogger system and it runs in the low to mid 9's and high 9's, low 10's on the street even.....and it had yet to fail.....but it had never really hooked either. Then one day we were shooting at some food, and up from the ground came traction. BOOM. That is all I will say. It hooked once.....once.....and that next day I was assembling a pair of 3.250" bore 9" cases with Detroit's with all the fixins....

To make an 8.2 live takes some prep but not too much. You gotta deburr the R&P to stress relieve the teeth, deburr the carrier, SANITIZE the housing- weld the tube's and the perches, straighten the housing and then pray to GOD.

To make an 8.5 or 12 bolt live, you pretty much have to do the same and thank GOD. The pinion shaft diameter is the same between the latter two and offer much increased strength than that of an 8.2 naturally.

You wouldnt believe the things we used to do to 8.2's in expermentation to help them out. I have even fit 8.5 BOP gears into an 8.2 housing for left hand turn guys just so them could make it live in a stocker class. I also used to pound a Ford 8.8 Trac-lock pre-load spring into an open carrier just to load the side gears to improve off corner biasing......only because we couldnt use a posi...but that didnt stop me either as I have also snuck a 8.5 BOP posi into an 8.2 housing as well.

But how much time and effort does one needs to take before making the appropriate choice to a more suitable differential?

John Break in for a track only car isnt really a problem. You never really build the heat in a "drag race" (sorry if I am assuming incorrectly) application, so it is left up to the one who maintains it. The biggest problem with a chassis on the street in heat related oil failure in its initial run in. If you cook the oil, it breaks down and can not do what it is required to do.....in a race car that only 'see's 1320 at a time.....its really no big deal. But I would recommend a good 30 minute break in on a rack or solid stands in high gear at idle. It would be even better if you could load it some, to keep applied pressure on the drive side....instead of bounching between drive and coast. But never the less, just to run it and check for any problems would be a good move.

First off I found this very interesting! To Chicane, I have an 8.2 with Eaton posi and 3.73 gears. I was told to break it in for 500 miles using 80/90 dino oil and GM posi additive. I was also told to keep the trips short and cooling times long. Now for the questions. How long do I keep the trips short? Do you agree with the oil type for breakin? Do you think the additive is necessary? How long would you recommend I wait to go synthetic or should I stay with dino oil? I think thats it for the questions and I am glad I read about those covers as I was going to order one!

Thanks Tom -- good info. I'd heard about the 8.5" carrier into the 8.2" housing trick before --- sounds like it would be a real PITA getting the correct pinion depth. Wouldn't you have to machine the housing an extra .15" deeper to get the correct pinion depth? Since the 8.5" ring gear is .30" larger in diameter? Or did you machine the 8.5 carrier down and run an 8.2" R&P?

I feel better about the whole thing actually -- I did set up the R&P so that the pattern WAS deep on the drive and centered on coast like you describe. The install sheet from Richmond showed this pattern as ideal for my gear set, so that's what I shot for.

I followed Richmond's specs exactly -- even so far as to get backlash at exactly .007-.008" all the way around. I did probably use a little less preload than you are describing, but I installed the carrier a little differently too. Rather than hammer on the carrier I installed the driver's side shim pack, then the carrier, then tapped the passenger side shim pack in with a 5 lb hammer and punch. It was tight enough that the punch left marks on the shim pack and I needed a crowbar to get the carrier back out. That was with .007" of extra shim after I found the spot where I could not quite remove the carrier by hand.

I found it interesting that the pattern on my new R&P was on the part of the teeth that did NOT break on the old set. That led me to believe that the pattern was too shallow on the old set although wear looked fairly centered on both drive and coast . . .

I think the thing that contributed to the old set failing was that I had replaced the carrier once before and was a little concerned that the backlash measured .014" when I pulled it out. I set up the new one at .011" with way too little bearing preload. I think that may have been what killed it. Probably should have preloaded it correctly, ran it at .014" like I pulled it out, and run the thicker oil.

I agree that a man with experience setting these rear ends up is a real asset -- but you guys had to start somewhere, right?

I agree that setting the differential bearing preload is something that you develope a feel for. It isn't easily measured with a gauge. I also would guess that the gear contact pattern was probably not favoring the toe side enough. Under pressure the contact pattern will move to the heel side, so it needs to be set to the toe side when setting up the gears. The top fuel and other top drag gace class teams will spend many hours deburing gear sets. It does help increase the life of high impact gears. As for the aluminum covers, even if the preload bolts don't work, the thick aluminum cover has to strengthen that huge hole in the back of the housing.

Tom,
It's too bad there are so many miles between us. I'd like to get together some time and shoot the bull and listen to some war stories. graemlins/beers.gif

Deerhunter~ I dont think that the initial break in is or will be effected by the choice of dino or a syn fluid (depending on manufacturer). What can matter is the weight....the higher viscosity, the longer it takes to build heat, the further you are from a temperature related breakdown (the most common type of failure).

Here is some of what I tell my customers. There is more, but this covers the hot topics:

1) 80/90wt is good for cold climates and front end differentials, or standard passenger cars that are not driven hard when cold...somewhat like a drag race application where cold flow can be a problem.

2) 140wt is a good place to start for trucks, motor homes, emergency and tow vehicles and performance street and racing use. There are also some applications where I run up to an ISO 350wt oil in off road trucks, land speed racing and the like. But my mainstay is 140wt for anything on the street, with the exception of front end differentials. FYI, in the 12 bolt that resides in my 67, I am currently running an ISO 250wt, suspended-moly, parafin based gear oil (Schaeffer's oil products, 209 suspended moly).....and I know some are probably saying..."WHAT!?!!". But yea, this car never see's freezing temperatures and is driven very hard as a 'test bed' for various applicable projects....so many, it is frightening.

3) Break in should have at a minimum of 5 temperature cycles up to running temperature and back down to ambient. I just told you 5 I know, but I will tell you 6 to 8 is my quoted norm. The 5 is a BARE MINIMUM.....anyless and I will not warranty the parts....and believe me, I can tell weather or not you did 5 or more or 5 or less.

4) Additive is necessary in a limited slip. I prefer the FORD HD friction modifier myself, but the RedLine stuff is good too. One four ounce bottle is enough for passenger differentials, I have run up to three in larger differentials like DANA 80's and 15000GVW Eatons.

5) You can run a fully syn oil right from the beginning. There is nothing bad about crude or parafin based oils, in fact some of them are better than the fully synthetics. BUT A GOOD QUALITY OIL IS PARAMOUNT. I will however tell you what manufacturers that I like and dislike and provide you with reasons and technical data to support why. Plain and simple, I know what works and I know what has failed in various applications and/or environments.....some oils are truly better than others.

Eric~ Didnt have to machine the housing at all. The bearings used had dimentions that worked with both the housing and set-up depth.

Watch out about using a punch and hammer on the carrier shims. One little indention and its failure time. You wont notice until you pull the cover off the next time, but I have seen them break and weasel out on their own, right up to the point of differential failure when the carrier races open up. I have however done that little trick when using a 'super shim' kit. Because of their construction and materials, they will take more abuse than anything else....not to mention giving you dimentional changes of down to 0.003" for pre-load adjustment.

BGH~ Yea, I know what your saying, I have enjoyed the e-mails that we have shared over the past couple of years. Its always a good time to share ideas and the experience of these little black box devices we have so much fun with. Maybe I can squeeze a couple of extra days in my scheduled mid west trip...Oklahoma, Bama and Tenn are on the list right now....and thats right next door pretty much.....

graemlins/beers.gif

Yeah Tom, I'm using the super shim pack. Got it from DTS and I think it was the best $25 I've spent . . .

I have to hand it to you guys that run 8.2 and 8.5's at that level of performance and make them live. It goes to show you what attention to detail and using high quality parts will do for you. I built a Dana 60 for my Camaro. When I pulled the 8.2 and put the Dana in its' place, I could not believe just how small the 8.2 looked in compairison to the D60.
I have a new question for you all. I will be breaking in a new differential and a new engine at the same time. I have been doing some reading about full trottle loading of a brand new engine to seat the rings properly(it was in a different thread here on Team Camaro). That would go completely against the break-in methods I read for a ring and pinion.
Should I just take the car on 8 short 10min trips under light load, allowing the differential to cool completely between trips; Then on trip #9 hammer it to red line in all forward gears to seat the rings well?
Chris

I personally think that the hammer-it-to-seat-the-rings technique is a bunch of hooey. With modern rings and machining equipment your piston rings will seat within seconds of firing the engine.

Take it easy on both engine and differential . . .

Thanks Eric.
Traditionally I have taken it easy on any new engines for 500 miles or so. I have never had any leakdown problems, so I don't know why I even entertained that notion of running her hard from the get-go. I will do just that.......take it easy on both enginge and differential for a while.
Chris