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Mike - 74 Nova Baltimore, MD
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Looks like your heading in the right direction.

One other suggestion... on the Final rear end assembly process, put a little silicone RTV around the inside circumference of the yoke spines prior to installing the yoke onto the pinion. This step keeps gear lube from seeping thru the pinion splines.
Only put the RTV on the yoke splines. DO NOT put any RTV on the pinion spines... as the yoke would push the RTV into the pinion bearing.
 

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Discussion Starter #22
Looks like your heading in the right direction.

One other suggestion... on the Final rear end assembly process, put a little silicone RTV around the inside circumference of the yoke spines prior to installing the yoke onto the pinion. This step keeps gear lube from seeping thru the pinion splines.
Only put the RTV on the yoke splines. DO NOT put any RTV on the pinion spines... as the yoke would push the RTV into the pinion bearing.
Ok so with my mock set up and .030 shim and backlash set .010 this is the pattern I got on my ring.
20200917_165810[1].jpg
20200917_165747[1].jpg
 

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Mike - 74 Nova Baltimore, MD
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The Drive pattern seems to be in the middle of the ring gear tooth... but is a very thin contact pattern.
The Coast pattern still looks a little deep on the ring gear tooth.

If it was me, I would remove the .030 shim and try a .027 pinion shim to see how the contact pattern changes. if there is no improvement in the contact pattern, you can always go back to the .030 shim.
Remember to apply pressure/resistance on the ring gear when turning the pinion (both directions) to obtain the contact pattern.
 

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Discussion Starter #24
The Drive pattern seems to be in the middle of the ring gear tooth... but is a very thin contact pattern.
The Coast pattern still looks a little deep on the ring gear tooth.

If it was me, I would remove the .030 shim and try a .027 pinion shim to see how the contact pattern changes. if there is no improvement in the contact pattern, you can always go back to the .030 shim.
Remember to apply pressure/resistance on the ring gear when turning the pinion (both directions) to obtain the contact pattern.
I'll try that. I did apply drag as I was turning the ring with the yoke. Maybe my arms were worn out or I applied too much paint. lol
 

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I don't know if it is going to be right or not, but i agree with Rifraf, change to an .027" pinion shim and see what the pattern does,

It is completely no good they way it is now, un-runnable....that sharp edge arrowhead pattern on coast and sharp straight edge pattern on the drive side are both not good at all.....you want fuzzy edges all around on pattern, like feathering out primer on a spot paint repair, no hard edges.
Hard edges shown in the pattern is line-to-line contact meaning very narrow contact...it will howl or burn up if left like that.

I kinda think it has to go the other way, .033-.034" shim to move the pinion deeper into the ring, but it is so far off in pattern right now it can completely fool you so you've got to choose one way or the other to check and just observe pattern.

You should give this a look and check how your gears are made....there are two types of ring gear cutters....face milling, and face hobbing....pattern reading is somewhat different for each type, so it will help to identify what cut type you have.
Two-cut Vs Five-cut:
 

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Mike - 74 Nova Baltimore, MD
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it is so far off in pattern right now it can completely fool you so you've got to choose one way or the other to check and just observe pattern.
I agree with Ericnova that the most recent contact pattern shown is a little difficult to interpret... especially on the Drive side of the ring gear.

I have read that when trying to set-up a used/driven set of differential gears, you can not get a usable contact pattern on the drive side of the ring gear. In post #4, SixtyThree mentioned that they drove the car (a very short distance) with the new differential gears installed (see quote below).
I actually drove it for less than half a block... I heard a howling sound and turned around within a half block of my home and headed straight back to my garage.
I am not sure if this "test drive" is influencing the contact pattern on the drive side of the ring gear (since it was such a short drive).

I have also read that if you are trying to install a used set of differential gears, you might be able to get a readable contact pattern on the Coast side of the ring gear... so I have been basing my recommendations on the Coast side contact patterns provided (but until a new pattern is observed after the pinion shim change, it is only my best guess which may to go).
409743
 

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Discussion Starter #27
Ok here it is at .027. backlash was within .010.
20200920_114637[1].jpg
20200920_121656[1].jpg
20200920_121709[1].jpg

I agree with Ericnova that the most recent contact pattern shown is a little difficult to interpret... especially on the Drive side of the ring gear.

I have read that when trying to set-up a used/driven set of differential gears, you can not get a usable contact pattern on the drive side of the ring gear. In post #4, SixtyThree mentioned that they drove the car (a very short distance) with the new differential gears installed (see quote below).

I am not sure if this "test drive" is influencing the contact pattern on the drive side of the ring gear (since it was such a short drive).

I have also read that if you are trying to install a used set of differential gears, you might be able to get a readable contact pattern on the Coast side of the ring gear... so I have been basing my recommendations on the Coast side contact patterns provided (but until a new pattern is observed after the pinion shim change, it is only my best guess which may to go).
View attachment 409743
 

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Mike - 74 Nova Baltimore, MD
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To me... the Coast pattern is looking better, but still a little deep.
The Drive pattern also appears to be a little better (looks to be spreading out across the tooth).
I think you are going in the right direction.

I would try a .023 - .024 pinion shim next to see if the pattern improves.
I know we are taking small steps with pinion shim adjustments, but I found that it is better to make small moves rather then to overshoot with regards to pinion shim changes.

Be sure to keep the same preload on the pinion bearing during each change.
 

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Yes, I agree ^^^. Both sides are looking better, try a thinner pinion shim next.

When you set up the next thinner shim pattern check, try both .010" and .006"-.007" backlash if you can and post pics of both.
 

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Discussion Starter #30
To me... the Coast pattern is looking better, but still a little deep.
The Drive pattern also appears to be a little better (looks to be spreading out across the tooth).
I think you are going in the right direction.

I would try a .023 - .024 pinion shim next to see if the pattern improves.
I know we are taking small steps with pinion shim adjustments, but I found that it is better to make small moves rather then to overshoot with regards to pinion shim changes.

Be sure to keep the same preload on the pinion bearing during each change.
Ok here's .024. Sorry I didn't take a pick of the backlash as ericnova requested. This one looks to be centered heel to toe but too close to the root dont you think?
20200921_115146[1].jpg
20200921_115126[1].jpg
 

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Mike - 74 Nova Baltimore, MD
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I appears that the contact pattern using the .024 pinion shim did not change that much from the .027 pinion shim. I was expecting to see a little more contact area sweep on both the Drive and Coast side of the ring gear.
This one looks to be centered heel to toe but too close to the root... don't you think?
I agree. I'm tempted to suggest a .014 -.015 pinion shim to see if the contact pattern moves into the top (crown) of the ring gear. If the contact pattern does move more on to the crown of the ring gear teeth, at least you'll know that the correct pinion shim should be in the .020's range.

P.S. Thanks for providing the detailed photos!
 

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Before you try a different pinion shim, check it with .012-.014" backlash and with .006-.007" backlash. You may already be in the sweet spot with pinion shim and just need correct backlash.

Drive side pattern moving closer to the root is a good thing, that is where the tooth is the strongest.
 

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Discussion Starter #33
Before you try a different pinion shim, check it with .012-.014" backlash and with .006-.007" backlash. You may already be in the sweet spot with pinion shim and just need correct backlash.

Drive side pattern moving closer to the root is a good thing, that is where the tooth is the strongest.
This is the latest with .020 which was taken before I read both yours and rifraf's suggestions. Also backlash was right
.010.

20200922_153045[1].jpg
20200922_155710[1].jpg
20200922_155753[1].jpg
 

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Discussion Starter #34
Before you try a different pinion shim, check it with .012-.014" backlash and with .006-.007" backlash. You may already be in the sweet spot with pinion shim and just need correct backlash.

Drive side pattern moving closer to the root is a good thing, that is where the tooth is the strongest.
Here's the latest with backlash set at .006 and a .020 pinion shim.
20200923_121619[1].jpg
20200923_121636[1].jpg
 

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That may be as good as it is going to get back at .024" pinion shim. Coast hasn't really changed but looks feathered a little better, looks to me like the drive side feathered out just a smidge better than the last at .020".

does opening the backlash up to .012-.014" do anything?
 

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Mike - 74 Nova Baltimore, MD
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Ericnova, I was thinking the same thing. I was expecting to see the pattern feather out a little more (or move towards the crown) as the pinion shims got thinner... but that didn't happen. The Drive contact pattern didn't change that much as the pinion shims got thinner. Kinda had me a little stumped.

I was leaning towards the .027 pinion shim @ .010 backlash, as I thought it provided the best Coast pattern and still had a slightly feathered Drive pattern within the center of the tooth (very similar to the .024 shim). I agree that a pinion shim setting from .027 to .024 might be the sweet spot for these gears.
 

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Discussion Starter #37
That may be as good as it is going to get back at .024" pinion shim. Coast hasn't really changed but looks feathered a little better, looks to me like the drive side feathered out just a smidge better than the last at .020".

does opening the backlash up to .012-.014" do anything?
I want to say back when I was at .027 and .030 I was in that range. This was the first time after several opening and closing the carrier to shim either left or right that I got within .010 or right at .010..
 

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Discussion Starter #38
That may be as good as it is going to get back at .024" pinion shim. Coast hasn't really changed but looks feathered a little better, looks to me like the drive side feathered out just a smidge better than the last at .020".

does opening the backlash up to .012-.014" do anything?
Just want to say thanks to you both for your time. You both invested a lot of time examining all my results and guiding me in the right direction. I feel like I just graduated from Ring and Pinion class 101. Again thank you. I will start the final assembly with the permanent bearings and shims now. I'll I reveal the results soon.
 

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Discussion Starter #39
I want to say back when I was at .027 and .030 I was in that range. This was the first time after several opening and closing the carrier to shim either left or right that I got within .010 or right at .010..
So far I've got it completely assembled. just need to add the gear oil, drums and tires then it's time for a road test. I got the backlash set within.010 and went with .027 for the pinion. Here are the results. Wish me luck!
20200924_174338[1].jpg
 

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One thing I didn't hear anybody mention is your pinion depth measuring method. I have one of those style measuring tools, and they work just fine, but it takes a little more to set up. The measure off the flat and bolt hole for the main cap. Which is fine, but that split is not always centered. You have to torque the main cap down and measure the inside diameter. Then take the cap off and measure from the machined surface down to the bottom of the race bore. This will tell you how much more you need to add or subtract from your static measurement.
 
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