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Old 02-22-2013, 12:48 PM   #1
Korevette
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Default Differential Pinion shim... need advice

I think I am getting pretty close to matching my original pattern of my used gear set by referring back to the marking paste, photo's and measurments taken prior to overhaul. I now have the back lash set at the original .008 and original pinion shim at .027.

To also assist with duplicating the pattern, prior to the overhaul, I measured the depth of the pattern on the the Drive side from the 'top' of the gear tooth to the 'bottom' of the pattern mark. The distance for the 'Toe' - the end of the mark to the edge of tooth was also obtained to help with the 'length'. Numbers were averaged out to give me a baseline.

In summary, with the overhaul using paste to measure, I am now .019 'shallow' on depth and the toe is .025 'short'. Coast pattern looks pretty good. I must say that 'paste' can throw you off, I have thinned if for accuracy.

As my backlash is right where I want it I am wondering if I move up to a .028 pinion shim to achieve a deeper pattern (seeking a .019 gain here), would the shim change have a slight change on the 'toe' distance?

As said the marking paste looks pretty damn good as compared to the original photo's. Am I 'splitting hairs' ? Maybe this is as close as I am going to get?
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Old 02-22-2013, 05:35 PM   #2
Solid LT1
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Quote:
Originally Posted by Korevette View Post
I think I am getting pretty close to matching my original pattern of my used gear set by referring back to the marking paste, photo's and measurments taken prior to overhaul. I now have the back lash set at the original .008 and original pinion shim at .027.

To also assist with duplicating the pattern, prior to the overhaul, I measured the depth of the pattern on the the Drive side from the 'top' of the gear tooth to the 'bottom' of the pattern mark. The distance for the 'Toe' - the end of the mark to the edge of tooth was also obtained to help with the 'length'. Numbers were averaged out to give me a baseline.

In summary, with the overhaul using paste to measure, I am now .019 'shallow' on depth and the toe is .025 'short'. Coast pattern looks pretty good. I must say that 'paste' can throw you off, I have thinned if for accuracy.

As my backlash is right where I want it I am wondering if I move up to a .028 pinion shim to achieve a deeper pattern (seeking a .019 gain here), would the shim change have a slight change on the 'toe' distance?

As said the marking paste looks pretty damn good as compared to the original photo's. Am I 'splitting hairs' ? Maybe this is as close as I am going to get?
When all else fails go with the pattern of the gearset. I have had out of the box gearsets not look good at all with the recommended pinion depth right on the $$. While math plays a role in setting up gear sets there is also a trial&error factor that may require disassebly and reassembly a few times. I use a honed out pinion bearing when setting up my gearsets. The bearing I use is a low mileage take out but sometimes when doing the final install with the new bearing pressed on the pattern goes to hell then you figure out what to do to get the pattern looking good (combination of pinion depth and backlash settings, I have gone out to 0.011" backlash on a used gearset to get pattern back to normal but this was a well used set of 4.56 gears for drag racing only and I didn't worry much about the "coast" side looking perfect and also run 140/250 Thick oil in that Diff.) Try the different shim or open backlash 0.001-0.002" in my book 0.010" is acceptible especially if your not trying to destroy the gearset doing autocross racing.
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Old 02-22-2013, 06:54 PM   #3
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Ask Tracdogg2. He is very good at diff's.
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Old 02-22-2013, 10:09 PM   #4
Korevette
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I went to the Gear Centre today and got some pinion shims. Is it OK to 'stack' these shims to get the desired thickness?
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Old 02-23-2013, 08:55 PM   #5
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I found a shim that will bring it to .0285. I will install it and see how much the pinion will move to the root.

With the increase of the pinion depth, can anyone tell me if this would have any effect on the 'toe' measurement?

Any comments are appreciated.
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Old 02-24-2013, 12:26 AM   #6
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Might want to take a look at the Google images for some information and gear patterns but, BEWARE there are some photos on there of some bad gear patterns.

Link: https://www.google.com/search?q=diff...75%3B501%3B318
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Old 02-24-2013, 04:14 PM   #7
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As you increase pinion depth the pattern will also move to the root. Increasing backlash will move the pattern towards the heel, more on the drive pattern than the coast pattern.
Yes you can stack pinion shims but if you are using a slip-fit setup bearing you will get a false measurement. The pattern will change once you press on the permanent bearing.
Trying to set up a used set of gears is almost impossible. The pattern is worn in and changing the pinion depth and/or backlash as little as
.001 will give you an odd shaped pattern. Choose a pinion shim and then keep changing the backlash. If you can't find the pattern then change the shim .001 and play with the backlash. You are looking for a big change in the pattern when changing the pinion shim. Don't go by patterns for new gears. You are looking for long drive pattern without the football shape or curves.
Mike
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Old 02-26-2013, 12:17 AM   #8
Korevette
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Thanks glackore, Solid LT1 and tracdogg2 for the replies and links. I think I have made some progress with this. I installed only one .0285 shim with my slip on bearings.

Mike, the pattern moved to the root and to the toe. My measurements as noted above has improved to bring it up to the existing pattern. Possibly the way I measured it is not the normal process but with 'paste' and measurements I am now within .001 on the root and only .006 shorter on the toe.

In trying to see if the pattern is copied, it looks very good to the original. The coast side improved.

One thing that changed was the 'backlash'. I was .008 and now at .007 to get these measurements.

Would these measurements be pretty close to eliminate any gear whine?

Dan,
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Old 02-26-2013, 01:29 PM   #9
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Dan,
Can you post any pics of the patterns? That would help a lot.
Mike
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Old 02-26-2013, 04:28 PM   #10
Korevette
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I will get those pictures up right away. I just need to search for the tutorial on how to do it. Stay tuned.

Dan,
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Old 02-28-2013, 11:31 AM   #11
Korevette
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Hi Mike, I sent you a PM and e-mailed the pictures with details.

Thanks again for your help.


Dan,
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Old 02-28-2013, 11:31 AM
 
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