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Discussion Starter · #1 ·
I'm new here and came across some helpful tech info while researching gear installs. In my case, I'm setting up a new set of Ford Racing 3.31 gears (face-hobbed) along with a Strange spool and new bearings/cups.

My question is with the pattern difference between the drive and coast sides. My understanding is that if the patterns are on opposite sides of each other, this indicates the pinion depth needs to be increased to bring the pinion closer to the ring gear.

I didn't have the original pinion shim as a reference, so I used a 0.030 shim as a start with 0.008 backlash. I'm using a mockup pinion bearing (new) that I honed out to allow for easy removal/install when adjusting pinion depth.

This is the pattern I got with a 0.030 shim and 0.008 backlash:

DRIVE
618200


COAST
618201


The hard parting line across the top of the drive side makes me think I need to go deeper (maybe a .032 shim), but the opposing patterns between the drive and coast confuses me.

I then tried a 0.033 shim with 0.009 backlash and got this...

DRIVE
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COAST
618203


Meh, not any better. So, then I tried a 0.040 shim with 0.006 backlash to see what the gear pattern would be. Sure enough, it moved it deeper but the pattern looked a bit more "balanced" with the 0.006 backlash.

DRIVE
618204



COAST
618205



Went with 0.036 shim and 0.006 backlash and the pattern got better with the drive and coast patterns.

618206


618207



Should I try a 0.037 shim with the same backlash, or am I going in the wrong direction?

Thanks in advance!
 

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Discussion Starter · #4 ·
BTW, I'll be using a solid spacer vs a crush sleeve and have not set pinion preload while setting pinion depth. What I do is, install the pinion gear along outer bearing and pinion nut, but leave out the oil slinger and seal. Then I snug the pinion nut down to eliminate any play and tighten just tight enough to have a slight drag as I turn the pinion yoke. Is this the correct procedure?
 

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Discussion Starter · #10 ·
Will do, but unfortunately for me I ran out of time to work on it. :confused: I'm going on vacation for a few days, but I'll work on it as soon as I get back.

I really appreciate the help and looking forward to getting this done. Thanks again!
 

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I was just joking on the vacation.
The best pattern is the first one. You have to get the coast and drive patterns opposite each other. This is what the pinion depth mainly does. once that is done the backlash will affect the shape of the pattern. The last pattern was the worst. Do a you tube search for "adjusting differential gear pattern". Below is one of the best. I noticed that you are not keeping the backlash the same for all your patterns. The backlash should be the same each time, approximately in the middle range until you get the pinion depth sorted out. 0.005 is to tight for pattern checking. Copy and put this link in your search bar.

 

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High Performance Rear Ends
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I went back and looked at your other patterns and the pattern with .040 looks like it might have some potential. I don't know why it's all the way at the root, but as far as heel to toe it looks the best. Try it again and try more and less backlash and see what it looks like. The current path isn't going anywhere.
 

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the 0.036 pattern has the longest patch on the drive side but the coast looks buried in the root. these pics may be hard to read, I have been taking pics of the gears I install and find the angle of the camera and the local lighting can really alter how they look in person.
I would try .036 again andf add some BL to see if the coast will move toward the middle of the tooth
 

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More for Less Racer
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When you do the pattern check, stick an axle in and use it to rotate the gears through a dozen revolutions or more forward and backwards....and a little less marking compound so ir flares out better without being too gloppy and thick.
 

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Discussion Starter · #17 ·
Back from the mini-vacation, I jumped back on getting the gear pattern right. Now with a clearer head, I remembered that a while back I had purchased a Ratech Pinion Setting Tool. I left it sitting in the toolbox bottom drawer in its original box, essentially out of sight and out of mind.

Using the provided instructions I calculated needing a 0.034 pinion shim.

With the 0.034 shim I set the backlash at 0.008, which in my opinion appears to be a sweet spot.

These are pics from different angles and lighting in an attempt to show the patterns.

618264


618265


618266


618268


618267


618269


618270


618271
 

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Looks very good, no not perfect. I think the backlash at 0.008 helped get a better pattern. The video I attached explains which way to go but only in very small increments, 0.002. Pressure on the gears will help the pattern. If you turn the pinion, wedge a piece of wood on the ring gear and create some drag or leather glove on your hand.
 

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High Performance Rear Ends
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Still not right. Go back to the .040 shim and try different backlash settings and see how it looks. I see that you are using a spool with this. Stick an axle in it and use the axle to turn it several complete turns in both directions. If you have the pinion bearing preload set correctly this will give nice clear patern.
 
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