8 1/4 axle inspection.

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swifty

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I have a 72 dodge dart, LA360, comp 262., 727. I had a 3.21 sure grip installed this winter. It was a little noisy at first, a whine when light throttle at 35 to 45. It recently got worse. I had a local shop drive it and they thought it was ring and pinion. They quoted $1250 to rebuild.

My plan is to put together a 8.75. My problem is this will take a while and the driving season is short here. I want to pull the cover off the 8.25 and see what's going on inside. The question is what to look for? What would it take for me to rebuild myself? I can live with some noise but don't want it to fail.
 
I inherited a 3.55 decades and decades ago that whined when I got it. A customer of mine wanted one so I took him for a ride with mine; I was swapping it out anyway. Yeah hesaid, that would be OK, so we struck a deal, and he paid me to swap it into his car, a very sweet 72 Challenger. The deal was if he didn't like it, I'd buy it back, and he'd only be out the swapping labor.
Well, in his E-body, it was pretty noisey, so Hyup, I still own it. I think That diff came in my 69 Cuda that I bought in 1983ish. It's not half as noisey in my car. Over the years I have worked on the pattern and changed bearings etc, and nothing changes.

The point is, if it ain't putting metal-dust into the oil, they might go for decades and decades.My 3.55s must be over 40 years old and have always had a slight whine. That 69 was born with 3.55s
I recommend to pull a sample of hot oil out and check it for metal. If it's clean, put it back and drive it. But if it makes pretty swirling patterns when you stir it, well she may be on her way out.
 
I don't know about yours, but the 8-1/4 in my jeep has been making noise for years, and it's getting worse. Mine started with the axle bearing for the right axle shaft (wheel bearing). Unlike the tried and true 8-3/4, the axle bearing rollers ride directly on a ground surface of the axle shaft. That means when the bearing rollers go bad, they damage that ground surface on the axle. Pi$$-poor design if you ask me, especially compared to the separate, self-contained bearing of the 8-3/4 design. Now, yours could be the differentail bearings, or pinion, I don't know. I guess you could remove the cover, clean out the old lube, check the gear mesh pattern, look for tooth damage, replace the lube with fresh gear lube, and nurse it along for awhile.
 
Thw whine is really bad at 40mph at light throttle. If you step on it or let off it goes away. There is a whine at higher speed but not as bad.
 
Hard to say exactly what is is,some adjustment is possible,with a manual,a dial guage and an assortment of torque wrenches it is not difficult to do yourself.
My 8-1/4 is out of the car, i have yet to go through it. I have gone through all kinds of drive axles,they all are basically the same principals to check/set up.
 
I recently had my 8 1/4 redone with 3.91's. I found some US gear ring & pinion set. The USA gear you mention I think is not really from USA! US gear has been around a long time made here. However, it is not really easy to come by. Found mine on ebay and were the only ones. Try to find Richmond gear, Motive gear or US gear can be had from Toms differentials. Just look up Toms online. Try to stick with a known brand. Better if made here or even Mexico. But try to avoid ones made in Asia or India!
 
I have my buddy's lift lined up next weekend to look at rear end. One question I have is the pinion preload. In the field service manual it says 30-35 inch pounds, but this is with just the pinion installed. What should the measurement be with carrier and axles installed? I know you should record this reading before you tear down, but what is correct? I know to remove drums to not affect reading. I assume the carrier and axles will add to preload measurement.

Also I may be getting a head of myself but in the field manual they use the special tool to measure pinion shim then assemble the pinion with crush sleeve, then set carrier in and set up carrier. I do not have special tool so I will probably be re assembling several times. So do I set pinion preload and crush the sleeve last? Is there on order to assembly if you do not have the special pinion measuring tool?
 
That 30/35inch pound spec is a turning spec and is the amount of force necessary after the sleeve has been crushed, and the pinion nut torqued into the spec range. In the field,and for a newbe, it is best to obtain a crush-sleeve eliminator kit, if they are available.... because as you say, you may have to pop the pinion in and out several times to get the pattern right. The crush sleeves are supposed to be a one time deal. If you get the pattern too deep the first time, then there is no way to uncrush the sleeve.
Having said that;
I have dialed the pattern in with no crush sleeve in there at all, just paying attention to the pinion preload, to not make it too tight, and then after the pattern has been dialed in, then crush the sleeve on final assembly. I've never had a come-back, doing it that way. I've also,shhhhhhh, reused lots of crushed sleeves by installing a thick shim in there and recrushing that bad boy.

You cannot get an accurate idea of the turning torque with the carrier and axles installed. You can only guess. Some guys get pretty good at it.
Don't guess too tight, cuz that will overheat the oil, with subsequent parts failures.
Don't guess too loose, cuz that will allow the pinion to climb up the ring-gear, make noise, and with subsequent parts failures.
Before digging into this it's a good idea to have a selection of pinion depth washer/shims. Every pinion has an optimum depth setting, and altho the range is small, there is no way, without the tool, to know if your new pinion will want to be installed at the same depth as the old one. So you have to guess, and that starts by installing the old washer for the first try.
Every pinion is marked on the nose with a +/- marking. If your new one happens to be identical to the old one, then you may be in for a quick dial-in. But I've never seen that happen; the odds would be astounding.
 
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in case it's just a wheel bearing, I think I'd pull the axle shafts, first, and examine the axle shafts' wear surfaces, and the wheel bearing rollers for flaking, nicks, spalling, etc. It may or may not be 'your' issue, but it'll need to be addressed anyway if there is a problem with those parts. just my 2cents.
good luck.
 
Gonna open it up tomorrow. I got an bearing kit coming from oreilly's. If I need it it will be here Saturday. If I don't need it I can return it. One thing I looked for the yellow paint for checking gears and the parts counters people looked at me like I was asking for raw uranium. I have some white and red grease I can try. I also did find some prussian blue. I have a homemade carrier bearing adjuster. Another question how long should I make the shafts? Is 3' about right? Also my 8 3/4 axle is in the works. Having a housing narrowed soon. One other question, what size is the pinion nut? Thanks and wish me luck.
 
I went to an art supply store. I think I bought a tube of cadmium yellow, squeezed out a dollop and mixed it with some axle lube and used an acid brush to apply it to the ring gear teeth. If you don't have the special tool to hold the yoke, maybe you could hold it with a big a$$ pipe wrench, while you loosen/tighten the pinion nut.
 
went to an art supply store. I think I bought a tube of cadmium yellow, squeezed out a dollop and mixed it with some axle lube and used an acid brush to apply it to the ring gear teeth

Thought of that. If the white food grade grease or prussian blue I have does not work I will try that.
 
Pulled cover off and looked inside. One thing I found right away is there is no preload on pinion. The nut is tight and there is no play but it spins with no resistance. The carrier backlash was about right. There was very little run out. I am gonna pull the carrier and pinion today. Looked at gear mesh and they looked like they were running too deep to me. Should I worry about that now or try see what's going on with pinion?
 
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I am no expert at reading the contact pattern. At first I thought the pinion was too deep and a shim needs to come out. Now I think it may be okay because Is somewhat centered on tooth. It is definitely better than it was. If I would adjust how much should I move it. It is at .073 now with original shim. The other shim pack I have is .067.

20181029_192656.jpg
 
Seems a little off center to my eye. However, I am by no means an expert. May need others with more experience to chime in. What brand of gear set did you get? What ratio?
 
yup , thinner spacer needed. It is bit of a guessing game, unless you do these all the time. I bought an extra duplicate bearing and honed it out, so it was a light press fit, and used it for a trial bearing, until I got the depth I wanted. Then take it apart and do it for real, with the (unhoned) bearing. That makes it less painful to get it where you want it.
 
I went .10 thinner and it looks much better. I was able to get the shims that go behind the cup so I did not have to take the bearing off. I will go with that. I will get a crush washer tomorrow and get it together hopefully for last time.
 
I went .10 thinner and it looks much better. I was able to get the shims that go behind the cup so I did not have to take the bearing off. I will go with that. I will get a crush washer tomorrow and get it together hopefully for last time.
the pattern should be kind of "cloud" -shaped with no sharp edges , centered in both the drive and coast faces. You should also pry the diff carrier/r.g. away from mesh to simulate actual operation with load. If you don't have a FSM, maybe Google has some pics of proper mesh.
 
Some of my Cosmic thoughts.

I made my adjuster tools from two half inch Drive sockets that were broken welded them into the end of a piece of pipe that is approximately 36 in Long.
On the other end I used a spindle nut from a Subaru car. 36 mm I believe or 1 7/16 inch that I bought from Advance Auto Parts.
I made two of these tools so that I could have one on each side of the vehicle and then all I had to do was take the torque wrench from side to side instead of removing the tool inserting the tool then removing the tool and inserting it over and over.
I highly recommend that you get a crush sleeve Eliminator. It's a solid piece of round pipe steel that's about half an inch long or something like that. Ratech makes one.
 
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More Cosmic thoughts.

Using a crush sleeve Eliminator you set the pinion preload at approximately 12 to 15 inch pounds of rotating Force. That is of course with no seal installed when you're doing the setting up.
You need a dial indicator to set your backlash for your ring and pinion. This is where the tools that you make for the sides come into play once you get that backlash to around .006 and you start tightening the side Adjusters as you check your backlash and it has creeped out to eight or ten thousands then you would go and tighten the side the ring gear is on first as your turning on this side to bring the lash down.
So in other words you can adjust that backlash as your torquing the side adjusters down just by going to whichever side you need to adjust it looser or tighter.
 
More Cosmic thoughts.

Using a crush sleeve Eliminator you set the pinion preload at approximately 12 to 15 inch pounds of rotating Force. That is of course with no seal installed when you're doing the setting up.
You need a dial indicator to set your backlash for your ring and pinion. This is where the tools that you make for the sides come into play once you get that backlash to around .006 and you start tightening the side Adjusters as you check your backlash and it has creeped out to eight or ten thousands then you would go and tighten the side the ring gear is on first as your turning on this side to bring the lash down.
So in other words you can adjust that backlash as your torquing the side adjusters down just by going to whichever side you need to adjust it looser or tighter.
good stuff!
 
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