I took my entire 12-bolt out and had it sandblasted. While I was at it, I removed the axles and looked at them. I made a testing jig that held the axle exactly in place. I used ball bearing rollers on both ends, so that I could spin the axle freely and easily, and then moved a dial indicator into position on the outer edge of the flange, as shown in the pic.

The axle in the pic has .010" of runout, plus there is a noticeable wobble in the shaft. I am guessing this is no good, but does anyone have acceptable tolerances? The other axle appears pretty straight in the jig, and it has about .005" of runout.

So, my question is: do I need one axle, two axles or no axles? I do have a high speed vibration that kicks in at about 70 mph............

http://csgbenefits.org/axletest.jpg


;)

Dave,

Great picture.

I will have to double check my notes but, I believe the max runout is a .001".

.010" is a great excuse to buy an axle.

Max runout numbers are generally less than .003 from any of the manufactures.
Like Jody, I usually look for less than .001 as a 'good' axle and .002 as aceptable if it's just a street car and the bearing surface looks good - anything else gets replaced.

O man, those runout numbers are small, but understandable. I guess I'll call Moser and ask them.

thanks

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I'm not trying to be critical but, how do you know the run out is not in your jig ? My best reccomendation would be to have a machine shop, chuck the axle in a lathe to check your run out. It should be the same as your jig. If it is not, I would say that your jig is not at .000.

I'm not trying to be critical but, how do you know the run out is not in your jig ? My best reccomendation would be to have a machine shop, chuck the axle in a lathe to check your run out. It should be the same as your jig. If it is not, I would say that your jig is not at .000.

The jig is good. It has ball bearings and the axle spins freely and accurately. The axle is held in place and does not move, other than rotate. I have a mill and lathe in my garage (small ones), so I'm a little familiar with obtaining proper measurements. I'm not a professional machinist tho.

If I had a video of the axle, you'd clearly see the wobble. It's bent, there is no doubt. ;)

thanks

Again, not to be critical or demeaning but, have you checked your jig to a known straight axle ? Bearings themselves have a tolerance and your bearing holders, have a tolerance, and then mounting them in your jig, you have a tolerance. They can all add up to .005-.010 very easily. Your axle may be bent ! You have to test your jig with something known ! Also looking at your picture again, you are testing the flange's run out, not run out of the axle itself. The flange has a tolerance when it is assembled to the axle also. You also have everything mounted on wood, which can easily be way out of tolerance. You would have to have very good eyes if it is only off by .010.

Haha, the jig is terrific, and actually I have been using it for years to balance small tires and wheels, so it is dead-on. Mounting on wood workbench isn't gonna matter here. The axle only weighs a few pounds and the weight is directly over the mount. Rotating the axle exerts virtually no force on the jig.

Let me put it this way - someone who is legally blind would be able to see the HUGE runout in the bent shaft as it rotates. The dial caliper confirms the flange runout at .010". I did not bother checking runout on the shaft itself, as it is SO BAD there can be no doubt it is bent. The other shaft is pretty good, but since I'm gonna buy one, then I may as well buy a kit...........

:beers:

The jig is not the problem. You could do the same measurment with the axle sitting on a couple of V blocks, or with it installed in the housing.

They both bad.

When I put my disks on, I was looking for less than .005" runout at the outer edge of th 12" disk. No way you could come close to that with .005" at the flange.

The jig is not the problem. You could do the same measurment with the axle sitting on a couple of V blocks, or with it installed in the housing.

They both bad.

When I put my disks on, I was looking for less than .005" runout at the outer edge of th 12" disk. No way you could come close to that with .005" at the flange.


Excellent point Jim.......

If Dave has .010" runout at the flange, what would that be at the outer wheel diameter! I agree, it is not Dave's jig but, the axle.

Dave, I run all of my high performance differential needs through a local shop. They see it all and they recommend Moser for a great cost effective/high strength axle for a street car. I have been using these axles with my ZZ502/502 with no problems. Jegs and Summit sell them for around $235.00-$240.00 a pair.

Thanks gents. I think I'll go the Moser route then for 2 new axles. :thumbsup:


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