Setting Ring and Pinion lash

[BDA]

I think I'm ready to call it done but I'm hoping for a second opinion.


My backlash is just about 0,007 inch (0.1778 - call it 0.18 mm. spec is between 0.12 and 0.25 mm)
The bearing preload (measured by taping a string to the hub, winding it up and then measuring the force it takes to unwind it with a spring scale) is about 4 lbs (1.779 da N - call it 1.8. spec is between 1 and 3 da N).


Interestingly, the diff nut on the pinion side will not screw in any more (at least not with the motorcycle clutch tool I have). The diff nut on the crown gear side will loosen, of course. Since I'm in spec on both the backlash and bearing preload, I'm not too concerned. Is this something to be worried about?


I've attached a picture of my wear pattern. It's not as clear as it might be (I used a Sharpie), but it doesn't look too bad to me but I'm clearly not the expert.


Any comments, warnings, or congratulations would be greatly appreciated!

[jbcollier]

There are strong shadows in the photo but the pattern looks good: centred up and down and slightly biased to inside (toe).  What's it like on the other side.

PS: Prussian Blue is  cheap, works a treat and lasts a long time.  I'm still on my first tube from the 70s.

[BDA]

Thanks again, John. I'll probably get some blue. The Sharpie was just too handy. I remember reading how a guy set up a rear end at a race using lipstick! Viewing the other side was tough! I'll try to get a picture of a pattern. Is the other side the coast side or did I take a picture of the coast side?

[jbcollier]

Nope, that is the drive side.  I think lipstick would work as well.

[BDA]

I'm glad the drive side looks reasonable. I'll try to get a picture of the coast side today. I'm not sure my wife will lend me her lipstick though!

[BDA]

I finally got sort of a picture of the coast side. I spun the input shaft for what seemed like forever - in both directions - and this was all the pattern I could get. I painted the teeth with red then blue in hopes that it would stand out better, but there doesn't seem like there's much to see but it seems to me to be on par with the drive side.. I'm frankly tired of spinning that input shaft so unless somebody wants to warn me that a cataclysm is inevitable, I'll start putting this bad boy back together.


Thanks to everybody for their comments, suggestions, and analysis!

[jbcollier]

Still can't really tell.  A tube of Prussian Blue is cheap, most auto/industrial suppliers carry it.

[BDA]

What does it mean when you can't get a clear pattern to show up on the coast side of the crown gear? I bought some blue (not as easy as it should be) and painted four teeth on the coast side. The attached picture isn't very good, but it's the best one I could get. There is a faint pattern on the first painted tooth that looks pretty good - sort of "ovaly" and fairly centered in both directions and no sharp lines. What looks like a line down the length of the tooth is, I believe, a reflection of the tooth above. I must have run that area of the crown gear over the pinion over a hundred times both ways and didn't get more than a hint of a wear pattern.


So I'm not sure how much anybody can tell from that pictures (probably not much), but I'm wondering what is the significance of the wear pattern on the coast side. In looking at pictures of wear patterns, I found a forum where a guy was coaching another guy on the same journey I'm on and he said he wasn't so worried about the pattern on the coast side if the drive side was good. Should I be concerned as an indication of the general health of the gears? Since pinion depth isn't adjustable, the only adjustment for the ring & pinion is the amount of backlash, right? Is there some adjustment that would impact the wear pattern on the coast side?

[jbcollier]

Lightly  clamp vise-grips to the input shaft spline.  Apply hand pressure against the ring gear moving and rotate the input shaft through a ring gear rotation.  Where you applied bluing should show clear where the teeth contact, and the pattern should be printed on other teeth as well

[BDA]

Thanks for the tips.


I've posted new pictures of the coast and drive side. The coast side has a bit more of a wear pattern. It is not as "ovaly" as the drive side and a bit further out toward the face than on the drive side. It has taken a lot of running the ring bear over the pinion to get the little bit of pattern I got on the coast side. The pattern on the drive side, however is more pronounced.


Comments? Suggestions? Advice?

[jbcollier]

The drive side looks good.  The coast side is "odd".  It may just be lighting, etc but it doesn't seem to have full contact.  It may whine when coasting though whether you'll hear it is debatable.

[BDA]

Thanks for checking up for me! That wear "pattern" on the coast side looked pretty strange to me, too. After spinning the input shaft as much as I did with so little effect to either the blue or Sharpie, I was wondering if it was making contact too even though I put pressure against the ring both radially and axially. If it might whine when coasting, I think I can live with it - if I even notice it.