Ring and pinion - help reading pattern

[talbotdd]

Hey everyone,

I am working on my first ever attempt at changing the gear set in my GM 8.5 10 bolt. I am having trouble reading my pattern.
I tried using the Ratech pinion depth tool to set pinion depth without much success. Even taking 8 measurements and averaging them left me a little unsure. My jegs kit came with the following shims:
(3) .020
(1) .028
(2) .029
(1) .032
(1) .039
(2) .041

According to the Ratech tool the .032 was too shallow by .005 so I went with the .039 since that was my only close choice.

Anyway, here is my pattern with the .039 shim. Backlash is at .007 right now


Drive side:





Coast side:






Any tips on where to go from here? My interpretation is that I am close, but may need a slightly larger shim. Any input you have would be greatly appreciated.


Thanks,
Dustin

[WSSix]

Ignore your pinion depth measurement as it doesn't matter. The backlash and gear mesh pattern are everything. I'd try to get my money back for the tool. Have you made sure your backlash stays consistent while you make pinion changes and pattern checks. It needs to stay within the acceptable range at all times.

If you don't have an installation manual go here https://www.ringpinion.com/Downloads/installations.aspx and scroll down to Yukon Installation Kit. He has a lot of patterns shown and how you should move to compensate.

You look close honestly, but I'd make some adjustments to see what happens to the pattern. You might want to keep a note pad around to help you remember what the result of a movement was as you go.

Also, keep in mind that you may not get it right the first time. So long as you're not so far off as to cause damage, a noisy rear end can be fixed/adjusted to try and get it quiet. Yeah, it's messy but that's the only way to learn. Good luck and take your time.

[talbotdd]

WSSIX - thanks for the input, I appreciate it. I went back and downloaded the manual from jegs since it didn't come with any in the kit. It calls for .008-.010 backlash. I messed around with the shims and got my backlash at .009 now. My pattern appears to be pretty close now.





Think this is acceptable?

Thanks,
Dustin

[WSSix]

Glad you got your hands on a manual and adjusted your backlash. Not going to lie. I don't like commenting specifically on patterns via the internet. I'm sorry. I only like to see them in person. I just don't feel I can see properly through pictures. I also go back and forth between a manual and the pattern a number of times before I decide. I'm slow and like to take my time.

I can say you don't look bad. I'd check out the Yukon manual to see if it shows different patterns and what they are considered compared to the Jegs manual. I've found differences in the number of patterns shown as examples in various manuals.

One other tip that might help. The pattern left by the compound on the first clean tooth or two after you go through the marking compound area may help you see the pattern better.

[SlowProgress]

WSSIX is right that the pattern is what you are looking for. You can't have the pinion in totally the wrong spot and get a good pattern. But it is always nice to have a reference depth setting so you know you are close. The depth is written on the end of the gear so if you can get that established you don't have to worry about it any more. Then as WSSIX said you just need to shim for bearing preload and set the backlash. Sometimes you do have to buy extra shims to get it just right if you are setting up a GM style rearend. There is a lot of good information on various websites about how the pattern moves under load and what you are looking for. A couple of things my shop teacher told me that always made sense.

1. As the gears wear the pattern moves toward the outside of the ring gear. So you want to start with the drive pattern in the middle and slightly toward the inside since it will move outward with time.

2. Think about the thickness of the gear tooth. It is thicker and stronger at the base. So the pattern should be in the center of the gear tooth and slightly closer to the bottom of the tooth where it is thicker and stronger. If the backlash is all wrong the contact point is too far out close to the thin part of the gear tooth.

I also thought your patterns looked pretty good !