Differential gear tooth wear pattern?

[AR67GTX]

This new gear set is setting up a howl at light throttle cruise - disappears if given gas or if gas is let off of. Gear pattern looks good to me although only about 30 miles on it. Nice broad and wide contact pattern that seems reasonably centered between heel and toe. Anyone see an issue? Someone on my other thread suggested it could be a bad pinion bearing based on a similar experience.

 

[zyzzyx]

How much is the free-play between the gears measured at the O.D. of the ring gear? Without a contrasting color preset, I can't really tell.

 

[Coronet 500]

Sorry I can't make out a pattern, but is that wear in the root?

 

[Cranky]

Wipe off any gear oil real good and then using either white or yellow grease, paint the pinion gear (not the ring) real good and then rotate it through. That should show what the pattern is pretty good. I set mine up using a pinion dept tool and don't even bother checking the pattern anymore......it never looked right anyways but after testing several, they were quiet. At least they were broke in for the customer

https://www.ringpinion.com/Content/Book/Reading-and-Adjusting-Ring-and-Pinion-Tooth-Patterns.pdf

 

[AR67GTX]

The contact area doesn't show up in pictures too good. The contact area stops short of the root. I'll see if I can get something better tomorrow and measure the backlash play although I think it's pretty good from feel and shifting between drive and reverse.

 

[AR67GTX]

My guess at backlash apparently was not too good. Looks to be at .015 inch.

Didn't really have anything to paint the gear teeth with but I wiped the lube from them and took some pictures without the flash.










I'm taking it back over to my mechanic Monday and see what he thinks.

Thanks

 

[Yatzee]

Looks pretty damn good to me but the "proof in the pudding" is when they're installed and weather there's any noise on the drive or coast side. Looks can be decieving when it comes to patterns especially if the gears are new and not yet "worn" in.

 

[zyzzyx]

The pattern looks almost perfect, but if you say the backlash is 0.015, then you're too loose LaTrec! Should be 0.005-0.009. Need to moove it over.

 

[AR67GTX]

I'm hoping that tightening up the backlash is all that it takes. I'm going to carry it back over Monday and let my mechanic see what he thinks.

Thanks

 

[dvw]

I'm hoping that tightening up the backlash is all that it takes. I'm going to carry it back over Monday and let my mechanic see what he thinks.

Thanks

If it really has .015" backlash my bet is if you put in spec the pinion is a touch deep. Change the backlash, run the pattern. That will be the telling tale.
Doug

 

[AR67GTX]

I was wondering about that after visualizing it in my mind. Although the backlash can be played around with from both sides of the carrier - just about any adjustment to reduce it would have to move the ring gear towards the pinion gear and the pattern a little deeper towards the root I would think.

 

[AR67GTX]

Got my differential back today. The mechanic said he took it all apart but couldn't find anything wrong except the backlash had opened up. He speculated that possibly a bearing race didn't seat fully and moved under load. Said the tooth pattern looked perfect to him and the pinion depth was still just as he set it. He suggested I open the axle lash up from .010 to somewhere in the shop manual range so I'll do that.

Checked the backlash when I got home and it's pretty tight - not over .006 inch. I think the shop manual is .006 to .008 if I remember correctly. Plan to reinstall tomorrow and see what happens.

 

[zyzzyx]

I suspect everything will be fine now! Good thing you didn't incur any "Lost Parts" or charge for the repair.

 

[AR67GTX]

I suspect everything will be fine now! Good thing you didn't incur any "Lost Parts" or charge for the repair.

No cost and he threw in a new diff gasket also. Hoping for the best. Around here he is the go-to guy for driveline work and has an excellent reputation amongst the hot rod/muscle car guys.

 

[moper]

The cup shifting is a possibility but odd if he does a lot of diff work. But - the biggest tell is the backlash. If that is in spec, and the pattern looks good (I can't see your earlier pics on this PC) then you should be fine assuming the teeth weren't damaged by the "loose" backlash.

 

[Cranky]

I'm curious how you your guy sets up the pinion depth. Does he go entirely by pattern or does he have a pinion depth setting tool? I have a setting tool/dial indicator and quit bothering with the pattern except for a quick check to see how it looks after using the depth tool. All the pattern did was confuse me so if the tool says it's good it's good. The first several that I did got plugged into my car just to make sure the tool was telling me the truth. After setting up and testing 5 or 6 rears 30 years ago the trust in the depth setting tool is all I use anymore.

 

[AR67GTX]

I'm curious how you your guy sets up the pinion depth. Does he go entirely by pattern or does he have a pinion depth setting tool? I have a setting tool/dial indicator and quit bothering with the pattern except for a quick check to see how it looks after using the depth tool. All the pattern did was confuse me so if the tool says it's good it's good. The first several that I did got plugged into my car just to make sure the tool was telling me the truth. After setting up and testing 5 or 6 rears 30 years ago the trust in the depth setting tool is all I use anymore.

 

[AR67GTX]

Well, no joy in Little Rock - still making noise. It doesn't seem to be quite as loud but now it also seems to whine/howl some on coasting also.

I can not say for certain but I think he checks pinion depth by some means other than pattern. He disassembled it and said the pinion depth was unchanged from the original assembly. That seems to imply he is measuring it somehow.

I guess I'll drive it for now and take the entire car back over to him and let him drive it and see if that gives him any ideas. Right now I'm suspecting bad Richmond gears but he said he has had good success with them.

 

[dvw]

Pattern tells all. You can measure until your blue, The pattern is the telling tale. Most times you can use the existing pinion shim, the depth will be close. But the bottom line is the pattern. That being said not every gear set or housing is perfect. Some make a little noise.
Doug

 

[moper]

I use the pattern. I've never owned the depth checking tool. I setup with a checking bearing and the original shims, and work from there. It's not the fastest way, but the rears I've done are silent.
I've never had an issue with any manufacturer. I have had issues with improper break in that makes them noisy. Given it went together and had an issue, I'd not blame the gears. That's a setup issue at minimum, possibly a setup and break in issue if the process wasn't followed.