Pattern Check Please - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #1 of 16 (permalink) Old Oct 14th, 16, 6:18 PM Thread Starter
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Big Al
 
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Pattern Check Please

12 Bolt With brand new Truetrac and new US Gear 3.31

Swapped pinion ship from last gear (.024) and .010 Backlash (US Gear Specs .008-.012). 17 in/lbs preload.

I think it needs more shim but the question is how much more?

Thanks!




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post #2 of 16 (permalink) Old Oct 14th, 16, 7:16 PM
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Re: Pattern Check Please

I would go to .030,and .008 b.l. and see what it looks like


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post #3 of 16 (permalink) Old Oct 14th, 16, 7:40 PM
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Re: Pattern Check Please

I agree. The pinion is not deep enough.
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post #4 of 16 (permalink) Old Oct 16th, 16, 11:24 AM Thread Starter
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Re: Pattern Check Please

Quote:
Originally Posted by mino65 View Post
I would go to .030,and .008 b.l. and see what it looks like
Quote:
Originally Posted by big gear head View Post
I agree. The pinion is not deep enough.
Thanks guys, I have a .030 shim I will get put on. Any reason to go towards the tighter end of B.L.?

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post #5 of 16 (permalink) Old Oct 16th, 16, 2:42 PM
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Re: Pattern Check Please

Not really, just see what the pattern looks like and adjust the backlash from that. The pattern won't show how much backlash you need until the pinion depth is right. Sometimes gears make less noise with more backlash, so it might work out that you need to open it up some. My post was aimed at pinion depth and not backlash.


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post #6 of 16 (permalink) Old Oct 16th, 16, 2:51 PM Thread Starter
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Quote:
Originally Posted by big gear head View Post
Not really, just see what the pattern looks like and adjust the backlash from that. The pattern won't show how much backlash you need until the pinion depth is right. Sometimes gears make less noise with more backlash, so it might work out that you need to open it up some. My post was aimed at pinion depth and not backlash.
Good to know and thanks again. The first guy that built it said he likes a tight backlash with a lot of power because they will spread apart. They were noisy from day one and got noisier every trip to the strip. I'll play with it tomorrow when I get the shim swapped.

The car is quiet and I would really like to keep the rear quiet. Any detriment to going to the high end of the BL spec?
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post #7 of 16 (permalink) Old Oct 16th, 16, 3:32 PM
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Re: Pattern Check Please

Sometimes you need to go .005-.007 over the .484" total shim thickness in order to prevent the shims from backing out on the passenger side and to prevent the BL from opening up. The carrier needs some preload no doubt or they will open up.

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post #8 of 16 (permalink) Old Oct 16th, 16, 4:20 PM
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Re: Pattern Check Please

Be sure that all bearings are completely seated. If a bearing is not completely seated then it will eventually seat during use and will screw up all of your settings. Even the best set up will be ruined by an unseated bearing.

Be sure that you get the bearing preload set correctly. If you don't preload all of the bearings enough it will allow things to move around during use.

Backlash is similar to pinion depth. It is set so that the pattern is as good as you can get it. It probably doesn't matter much which end of the tolerance it's on as long as the pattern is correct. Yes, the gears are going to push away from each other under hard use, so if you want to run it on the tight side of the tolerance it won't hurt it. Some people have found that a gear with a little bit of noise will be quiet if the backlash is opened up just a little.


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post #9 of 16 (permalink) Old Oct 16th, 16, 5:21 PM Thread Starter
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Re: Pattern Check Please

Quote:
Originally Posted by big gear head View Post
Be sure that all bearings are completely seated. If a bearing is not completely seated then it will eventually seat during use and will screw up all of your settings. Even the best set up will be ruined by an unseated bearing.

Be sure that you get the bearing preload set correctly. If you don't preload all of the bearings enough it will allow things to move around during use.

Backlash is similar to pinion depth. It is set so that the pattern is as good as you can get it. It probably doesn't matter much which end of the tolerance it's on as long as the pattern is correct. Yes, the gears are going to push away from each other under hard use, so if you want to run it on the tight side of the tolerance it won't hurt it. Some people have found that a gear with a little bit of noise will be quiet if the backlash is opened up just a little.
You you say "completely seat", do you mean the races or just proper preload?

I have been playing around with the solid pinion spacer and I'm able to achieve 17 IN/lbs in both directions using the torque dial below. I used the same shim stacks from the original Eaton and the new Truetrac is a bit wider. The original eaton was snug but came out by hand. The new Truetrac was very snug and required my spreader to remove. It was actually dragging the carrier more than I would like so I plan to take a bit out when I re-set the BL. I have heard you can't over preload them but that seems hard to believe.



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post #10 of 16 (permalink) Old Oct 16th, 16, 8:50 PM
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Re: Pattern Check Please

When you press a bearing on you must check to be sure that the bearing completely seated. If there is a gap behind the bearing then it didn't seat completely. If it's not seated then it will seat later after use and then your bearing preload will be gone. If it's a differential bearing then your backlash is also going to change. Use a .001 feeler gauge to check the back side of all of the bearings after you press them on and be sure that they are seated.


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post #11 of 16 (permalink) Old Oct 17th, 16, 4:53 PM Thread Starter
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Re: Pattern Check Please

Alright, I put the .030 shim on and there was zero change. This might be caused by the 2 shims originally installed on the old gear. They were a little big and did not go on perfectly together. This caused them both do deform and cup making it hard to get a reading. I thought they were .009 and .013 for a total of .024.

Put the .035 shim on and got the pattern below with a backlash of .010. I took it apart to install the pinion seal and all readings were exact after re-assembly. I know it probably could use another .003 of shim but I am going to run it this way unless someone says absolutely not to. Thanks again for all the help everyone.



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post #12 of 16 (permalink) Old Oct 17th, 16, 5:47 PM
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Re: Pattern Check Please

Oh great. I can't see the pictures on this computer.


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post #13 of 16 (permalink) Old Oct 17th, 16, 5:49 PM Thread Starter
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Re: Pattern Check Please

Try these direct links. Google photos is goofy.

https://goo.gl/photos/d16wBzzAf8MfLihGA

https://goo.gl/photos/cAq5NsdLyGiL4ygz9

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post #14 of 16 (permalink) Old Oct 17th, 16, 8:23 PM
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Re: Pattern Check Please

Still not deep enough. Add about .005 more and see how it looks.


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post #15 of 16 (permalink) Old Oct 17th, 16, 10:19 PM Thread Starter
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Re: Pattern Check Please

Good news and bad news.

Bad news is because of Freddie's crappy computer I put everything back together before he replied so I blame him for me not getting the pattern perfect

The good news with all kidding aside is the gears are quiet and the Truetrac is working well. I think this setup will work until I get an aftermarket axle built. Thanks again!
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