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Discussion Starter #1
Hey guys, I just finished replacing my ring and pinion on my 63. The rear diff is not original. It's a 8.2 10 bolt and I went from 4:11 to 3:36. I measured the pinion depth to within .0002 of within spec but I haven't been able to check the backlash. Anyway here's a pic of the diff with the backlash paint. I'm pretty sure about the pinion depth being within spec but I just want to be sure and hoping someone with a trained eye can see where I may need to make some adjustment. Thanks for your input. This forum has been a great help.
20200906_144757[1].jpg
 

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Need to spin it through several revolutions to get a clear pattern....with positraction or spool i typically use one axle shaft to spin the whole thing. May not go so well with an open diff with that method, might just spin the spiders is all but you can try it.
Maybe a cordless drill and drive it through some socket adapters through the pinion nut??

Otherwise, just spin it through several times as best you can and see if we can get a pattern to develop. If you spin it with the pinion, you may need to wedge a couple rangs under the bottom of the ring OD to put some drag on things, so the marking compound will squish out and spread.
 

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i like to grab the ring gear in one hand to create drag and spin the yoke a few revolutions. and it looks like u need a touch more backlash to get that pattern more centered
 

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Discussion Starter #4
Need to spin it through several revolutions to get a clear pattern....with positraction or spool i typically use one axle shaft to spin the whole thing. May not go so well with an open diff with that method, might just spin the spiders is all but you can try it.
Maybe a cordless drill and drive it through some socket adapters through the pinion nut??

Otherwise, just spin it through several times as best you can and see if we can get a pattern to develop. If you spin it with the pinion, you may need to wedge a couple rangs under the bottom of the ring OD to put some drag on things, so the marking compound will squish out and spread.
Here's the pattern I get with drag. I actually drove it for less than half a block. Does the fluid take a minute to circulate through before quieting down? I heard a howling sound and turned around within a half block of my home and headed straight back to my garage. It looks to me like it's engaging evenly but what do I know being this is my first diff rebuild.
20200911_110715[1].jpg
 

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if that picture is the marking compound after having lube run through it, the pattern is washed away, you'll need to re=paste it and roll it through a few times for a pattern check.

if that was the actual pattern shown if fresh marking compound, something is bad wrong, and is so far off I can't tell you which way to adjust things....contact should not be full length and fill the entire contact surface.
How much backlash did you measure?? if you haven't got an dial indicator, get one....you cannot do the job correctly without it.
Without knowing your backlash adjust ment, first thought looking at that image is pinion depth is not right....how did you measure that??
Like the pinion istoo close to the differential(not deep enough in the housing).
How much pinion shim was used?
How did the shim used compare in thickness to the shim on the previous gear set.

Pattern images: Ideally, the first two boxes in each image below is what you are looking to achieve in the marking compound.

409503


409504
 

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Mike - 74 Nova Baltimore, MD
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I measured the pinion depth to within .0002 of within spec but I haven't been able to check the backlash.
It is my understanding that you need to have the backlash set to gear manufacturer specs prior to checking the contact pattern on the ring gear. You also need to check the drive side AND the coast side of the ring gear.

I like to cover 3-4 teeth of the ring gear at 4 different spots on the ring gear when checking the contact pattern. I also use an axle to turn the ring gear when checking pattern (posi)... or use a rag to hold the ring gear to create some drag on the ring gear if using the pinion to turn the ring gear. You also need to turn the ring gear several revolutions in BOTH directions (clockwise & counterclockwise) to check the drive and the coast contact pattern.

Below are some example of how pinion depth can effect the contact pattern on the ring gear. All patterns were achieved with with a .008 - .010 backlash. My final setup used the .037 pinion shim.
Drive 31-34-37P 8-10 BL.jpg

Coast 31-34-37P Coast 8-10 BL.jpg
 

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Discussion Starter #8
if that picture is the marking compound after having lube run through it, the pattern is washed away, you'll need to re=paste it and roll it through a few times for a pattern check.

if that was the actual pattern shown if fresh marking compound, something is bad wrong, and is so far off I can't tell you which way to adjust things....contact should not be full length and fill the entire contact surface.
How much backlash did you measure?? if you haven't got an dial indicator, get one....you cannot do the job correctly without it.
Without knowing your backlash adjust ment, first thought looking at that image is pinion depth is not right....how did you measure that??
Like the pinion istoo close to the differential(not deep enough in the housing).
How much pinion shim was used?
How did the shim used compare in thickness to the shim on the previous gear set.

Pattern images: Ideally, the first two boxes in each image below is what you are looking to achieve in the marking compound.

View attachment 409503

View attachment 409504
Ok so with the depth indicator I got from JEGS I got a reading of 0.930 and subtracted that from the extension on the tool which was 0.352 and came up with 2.053. Looking at the pinion I see 2496 stamped on the center. That number is the only one that makes sense. Am I going by the wrong number? If not then based on my finding it looks like I may need to add some shims.


20200912_132411[1].jpg
20200912_135319[1].jpg
 

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Pinion depth numbers i have always seen are acid etched or engraved in, put in one of those two spots buffed shiny in your picture.

They can't be stamped in, since they are determined well after the gear set is milled and heat treated, they are only determined after the gear set is lapped in later.

I would not expect that stamped 2496 to be the depth number.

As a general rule, gear sets are made to a tighter tolerance than the housing was....the shim is actually there to fit the loose tolerance housing to the tighter tolerance gearset, if you follow me.
The shim that was correct for the original gearset fitted to that housing is generally within about .003" of being correct for any gearset put into that housing.
Understand what I mean here?
it can just get fouled up of course if someone else set up a set of gears in the housing at some point in history between original and you and messed up that relationship, then the shim on the gear you removed won't be such an accurate guide.

We tend to thnk of it as the smaller pieces(gearset) being fitted to the bigger piece(the housing) but in reality it is the less precision machined housing being shim fitted to the more precision gear set. Once the shim was determined for the first assembly at the factory, it is going to be very close for any gearset change later, since the snim was selected for the housing.
 

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Discussion Starter #10
Pinion depth numbers i have always seen are acid etched or engraved in, put in one of those two spots buffed shiny in your picture.

They can't be stamped in, since they are determined well after the gear set is milled and heat treated, they are only determined after the gear set is lapped in later.

I would not expect that stamped 2496 to be the depth number.

As a general rule, gear sets are made to a tighter tolerance than the housing was....the shim is actually there to fit the loose tolerance housing to the tighter tolerance gearset, if you follow me.
The shim that was correct for the original gearset fitted to that housing is generally within about .003" of being correct for any gearset put into that housing.
Understand what I mean here?
it can just get fouled up of course if someone else set up a set of gears in the housing at some point in history between original and you and messed up that relationship, then the shim on the gear you removed won't be such an accurate guide.

We tend to thnk of it as the smaller pieces(gearset) being fitted to the bigger piece(the housing) but in reality it is the less precision machined housing being shim fitted to the more precision gear set. Once the shim was determined for the first assembly at the factory, it is going to be very close for any gearset change later, since the snim was selected for the housing.
One of the etchings
Pinion depth numbers i have always seen are acid etched or engraved in, put in one of those two spots buffed shiny in your picture.

They can't be stamped in, since they are determined well after the gear set is milled and heat treated, they are only determined after the gear set is lapped in later.

I would not expect that stamped 2496 to be the depth number.

As a general rule, gear sets are made to a tighter tolerance than the housing was....the shim is actually there to fit the loose tolerance housing to the tighter tolerance gearset, if you follow me.
The shim that was correct for the original gearset fitted to that housing is generally within about .003" of being correct for any gearset put into that housing.
Understand what I mean here?
it can just get fouled up of course if someone else set up a set of gears in the housing at some point in history between original and you and messed up that relationship, then the shim on the gear you removed won't be such an accurate guide.

We tend to thnk of it as the smaller pieces(gearset) being fitted to the bigger piece(the housing) but in reality it is the less precision machined housing being shim fitted to the more precision gear set. Once the shim was determined for the first assembly at the factory, it is going to be very close for any gearset change later, since the snim was selected for the housing.
The numbers that are etched in on one of the shiny spots is 14G197 and the other is just 0 0.
 

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What brand gear set??

Nothing etched on the OD of the ring?? No backlash("BL") number??
No paperwork/instruction sheet indicating a pinion depth or backlash recommendation??

What is backlash clearance right now?? I want to make sure this isn't way too tight or way too loose backlash just totally throwing off the pattern. Can't just geiuss at this.

Paint a few teeth again, run it through several revolutions in both directions to see if we can get a pattern to actually read.
If you'd just done that after posting the pic in post #1 instead of closing it up and driving it we might have a better idea what nees to be done.

What thickness pinion shim did you use??
What thickness was the old pinio shimon the 4.11 gearset you took out??
 

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Discussion Starter #12
It is my understanding that you need to have the backlash set to gear manufacturer specs prior to checking the contact pattern on the ring gear. You also need to check the drive side AND the coast side of the ring gear.

I like to cover 3-4 teeth of the ring gear at 4 different spots on the ring gear when checking the contact pattern. I also use an axle to turn the ring gear when checking pattern (posi)... or use a rag to hold the ring gear to create some drag on the ring gear if using the pinion to turn the ring gear. You also need to turn the ring gear several revolutions in BOTH directions (clockwise & counterclockwise) to check the drive and the coast contact pattern.

Below are some example of how pinion depth can effect the contact pattern on the ring gear. All patterns when achieved with with a .008 - .010 backlash. My final setup used the .037 pinion shim.
View attachment 409514
View attachment 409515
Thanks for sharing. The pic below is with drag using the procedure you recommended. It looks similar to your .031 measurement. I waiting on a new crush sleeve eliminator so I can do this over. I really appreciate your feedback as well as EricNova's.
20200913_172632[1].jpg
 

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Thanks for sharing. The pic below is with drag using the procedure you recommended. It looks similar to your .031 measurement. I waiting on a new crush sleeve eliminator so I can do this over. I really appreciate your feedback as well as EricNova's.
View attachment 409592
That is also the coast side of the gear teeth, the straighter flank side is the drive side and more important to get right.

Just offhand from only the coast side pattern, it looks like you need a thinner pinion shim, pinion needs to move away from ring ring, pinion head forwrd away from differential centerline.

Really need to see the drive side though. That's the side that matters the most to get right
 

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I agree with Ericnova. It is more important to see the contact pattern for the Drive side of the ring gear... but based on the pattern shown on the coast side of your ring gear, I also agree that the pinion looks too deep (if the backlash was set correctly).

When I was at .031 pinion shim, my coast pattern (and drive pattern) was more towards the Crown of the ring gear, indicating the need for increasing the thickness of the pinion shim.

Looking at the photo of your coast pattern, it is more towards the Root of the ring gear, indicating the need for decreasing the thickness of the pinion shim.
409604

Note: It took me 3 times setting up my rear to get the correct pattern.... and then one addition time to un-assemble & reassemble the entire set-up with the pinion spacer and pinion seal (I also did a another pattern check on the final set-up to confirm nothing changed). You do not need to install a crush sleeve and pinion seal until you get a decent ring gear pattern... just set the pinion bearing preload without the crush sleeve until you go for final assembly.

I also used a pinion spacer instead of a crush sleeve. A little more time to set up... but works great once you get the pinion bearing preload within specs.
 

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Discussion Starter #15
I agree with Ericnova. It is more important to see the contact pattern for the Drive side of the ring gear... but based on the pattern shown on the coast side of your ring gear, I also agree that the pinion looks too deep (if the backlash was set correctly).

When I was at .031 pinion shim, my coast pattern (and drive pattern) was more towards the Crown of the ring gear, indicating the need for increasing the thickness of the pinion shim.

When you were at .031 pinion shim, your coast pattern was more towards the Root of the ring gear, indicating the need for decreasing the thickness of the pinion shim.
View attachment 409604
Note: It took me 3 times setting up my rear to get the correct pattern.... and then one addition time to un-assemble & reassemble the entire set-up with the pinion spacer and pinion seal (I also did a another pattern check on the final set-up to confirm nothing changed). You do not need to install a crush sleeve and pinion seal until you get a decent ring gear pattern... just set the pinion bearing preload without the crush sleeve until you go for final assembly.

I also used a pinion spacer instead of a crush sleeve. A little more time to set up... but works great once you get the pinion bearing preload within specs.
So here is a pic of my pinion and as you can see the only etched info is on top. There is no info on the shaft and as for the ring it has the exact same information that is on the pinion. the next pic is of he base of the bearing and you can see I have two shims. The shiny shim is new the other is the original shim that came off of the previus but not original 4:11 set up that I removed. My plan is to carefully remove the bearing without destroying the outer cage,use my mock up bearings and try to dial it in but this time use my caliper that just came in today to measure the shims in order to get the correct backlash.
20200914_143540[1].jpg
20200914_143613[1].jpg
 

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If you can, put the old pinion in with it's original shim, and take a depth measurement off of it....then use that same depth measurement as the starting point for your new gear. Then put about .010" backlash in the ring gear and take a pattern check

Just looking at your pic of the new pinion w/bearing and shims....looks like you have TWO shims of about .030" on there? Nearly .060" total??
If so, that is definately wrong.

What was the thickness of just the original shim?

Wow, I have never seen a gear set that didn't have depth and backlash figures etched on it, just leaving you to fly blind using nothing but pattern checks to guide you.

This is a Quick Performance house brand gearset?? or an Ebay special?
 

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Discussion Starter #17
If you can, put the old pinion in with it's original shim, and take a depth measurement off of it....then use that same depth measurement as the starting point for your new gear. Then put about .010" backlash in the ring gear and take a pattern check

Just looking at your pic of the new pinion w/bearing and shims....looks like you have TWO shims of about .030" on there? Nearly .060" total??
If so, that is definately wrong.

What was the thickness of just the original shim?

Wow, I have never sen a gear set that didn't have depth and backlash figures etched on it, just leaving you to fly blind using nothing but pattern checks to guide you.

This is a Quick Performance house brand gearset?? or an Ebay special?
It's both a Quick Performance on Ebay. I also bought a set of spider gears and the master bearing set from them. I had to be the one that gets the pinion gear without the depth and backlash figures etched on it. I'll take a measurement of the original shim.
 

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Discussion Starter #18
If you can, put the old pinion in with it's original shim, and take a depth measurement off of it....then use that same depth measurement as the starting point for your new gear. Then put about .010" backlash in the ring gear and take a pattern check

Just looking at your pic of the new pinion w/bearing and shims....looks like you have TWO shims of about .030" on there? Nearly .060" total??
If so, that is definately wrong.

What was the thickness of just the original shim?

Wow, I have never sen a gear set that didn't have depth and backlash figures etched on it, just leaving you to fly blind using nothing but pattern checks to guide you.

This is a Quick Performance house brand gearset?? or an Ebay special?
So I got the bearing off of the pinion and found that I had replaced the original .030 with two .015's and one .010. The reason I did that was cause the original .030 was slightly damaged. I went over .010. Bad doggy. Ok now I'll start with .030 and start checking my backlash from there.
 

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Maybe give quick a call tomorrow and ask why there is no depth, backlash, or any other set-uo information with/on those gears?

They have set-up techs putting assemblies together on a regular basis, they may have some guidelines already figured out for the gears they sell.
 

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Discussion Starter #20
Maybe give quick a call tomorrow and ask why there is no depth, backlash, or any other set-uo information with/on those gears?

They have set-up techs putting assemblies together on a regular basis, they may have some guidelines already figured out for the gears they sell.
So I reached out to Quick Performance and they said if there's no specs marked on the pinion or ring then to just start with .030 and work from there. Easy enough given that's what was in the original set up.
 
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