First I have fought with this several times, I have plenty of experience with rebuilding differentials and am far from a novice but this thing is driving me nuts. I have conflicting information from several different rebuild guides that do not match the Honda OE info. I can not seem to get a good contact going from the smallest pinion shim clear to 0.020" above, with 0.002 or as high as 0.005 backlash it seems to make no change for the better. I am including pictures of the patterns / Honda info / misc online info.

I ran the diff at 0.005 backlash with a contact similar to the ones below for a short time but I got tired of fighting with it, it whined on coasting / part throttle and was annoying as hell.

I am rather confused, old school method is toe in on drive heel on coast is backlash, but OE spec is so low and I am within that spec and have ran it with excessive backlash to get almost the same pattern.
I have preload on the pinion at approx 18-25 inchs lbs, I am preloading the side bearings so the carrier does not require excessive force to turn but does not spin easy, I do not have a push / pull lb gauge as the instructions call for but have set up some similar toyota / ford third members and put this ones preload similar to the toyota in feel.

I do have the upgraded carrier with ARP bolts / straps, I am wondering if something is amiss with the carrier I was provided.

The only positive is I can pull and take the third member apart in less then an hour now lol, Stud removers do wonders for not having to take the back brace out with the diff.

 

If any one needs more pics / info let me know, its on my workbench and well, I own the shop so I can take a few mins to get more info as needed. I might snap some pics of the pattern with the +0.020 just for reference.

I am very inclined to believe that the noise is a preload issue and that this pattern is ok according to other real ends I have rebuilt in the past, in most cases I have heard the initial contact point will expand inward as load is applied to the gear. The problem is the OE info says it should be right dab in the middle.............

So who knows better, old school for 9inch guys or Honda.

 

Contact S2KPUDDYDAD https://www.s2ki.com/forums/members/s2kpuddydad-36094/ I'm sure he could go through everything over the phone.

 

Looks too much like contact with the root of the gear tooth. I've always setup diffs with central face contact, going a little towards the toe on drive, a little towards the toe on the drive side, but we're talking small amounts, not near as much as shown in your pics.

Is that the pinion preload spec in the FSM? I've setup about a dozen R200s, and a couple Toyota solid axle third members, and I seem to recall shooting for about half that pinion preload. An improperly preloaded pinion bearing (low or too high) can be noisy on coast or light throttle for sure. I've had a Toyota third member that had the pinion crush sleeve crush down on me (as they love to do), and got bearing preload way below minimum, and it chewed the bearing up noisily over time. I seem to recall loudest on coast and light throttle.

5 thou of backlash doesn't seem that excessive to me, but it does depend on how the gears are ground, so there's no magic number there. Less backlash is generally quieter.


I have found that high backlash gears that are still setup well will really quiet down if you put some thick oil like STP oil treatment in there. Not something I'd recommend for a long term solution, but bearings will not quiet down with thicker oil, but backlash usually does in my experience. Maybe worth a quick experiment.

 

The OE spec for preload is approx 7.5-10 inch lbs plus the none preload rotational torque, To be perfectly honest I am going more by the original which was around 20 total and several others have set theirs up that way.

I am going to try setting it up with significantly less pinion depth and see what it runs like, I am kind of wondering one of the new bearings is out of spec or maybe the carrier is bad?

 

Following this thread since I want to learn how to read these markings. I have a negligible amount of experience setting gear tooth contact patterns.

But at first glance, it seems you have too much Toe Contact. You may want to torque the pinion nut a bit more to crush that spacer slightly more and bring the pinion away from the center of the ring gear.

 

The pinion depth is not adjusted by tightening the pinion nut. The depth is adjusted by the shim thickness that goes in between the pinion gear and inner bearing. The crush sleeve is used to put resistance on the bearings / pinion nut so that you can apply 95+ ft lbs to it without crushing the bearings, the bearings are not intended to have that much force applied to them, the measurement of the force applied to them is the pinion rotating torque.

 

a bad diff bearing usually sounds much lower frequency than a bad tooth contact pattern. Number of rollers vs number of teeth being the diff.

less pinion depth and then moving the ring gear in a tad might help.

ive never run that much pinion preload, so it still seems odd to me. That could be causing noise, as that's a bit of crush on the pinion bearing. 8-10 in lbs sounds much more reasonable.

 

Step 11 is measure the rotating torque of the pinion assembly before tightening the lock nut.
Step 13 outlines getting proper preload, it lists the preload spec as 7.8 in lb - 12.1 in lb + TP from step 11.

20 inch lbs of preload isn't much, I have rebuilt many f150 / c1500 / ect diffs and most call for 20-40 in lbs of preload. A lack of preload will cause the bearings to thrust forward on decel / back on accel, leading to noise.

I am more concerned that I do not have the side bearing preload set correctly as they want you to use a push / pull lb meter on the carrier bolts to measure the preload. Which I do not have. I have just been going by what is "normal" for other applications, but to be honest, I have seen riding lawn mower diffs with a bigger ring gear then this thing....