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7.5 Ring and Pinion Pattern

Discussion in 'Transmission / Rear End' started by Rocket Powered, Feb 12, 2018.

  1. pontiacgp

    pontiacgp Canadian Prime Minister

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    The reason I asked about the crush sleeve is that if it not collapsed enough that would be the reason for a pattern that is too deep with no shims. The bearings would also not be seated properly........
    [​IMG]
     
  2. 64nailhead

    64nailhead Master Mechanic

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    I agree. Crushing the crush sleeve is with the differnetial and housing in the car is, borderline, an art, but definitely a PITA. But no matter of the situation, that should and can be addressed later as the crush sleeve should not be installed during rear end setup. The crush sleeve is the needed on the final step of the setup.
     
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  3. Rocket Powered

    Rocket Powered Not-quite-so-new-guy

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    I set up without the crush sleeve during inspections. I tried setting preload to summit spec, 25in lbs. I could not turn the yoke. Drag was severe. Did research, found for a Gm 7.5 preload 12-15 In lbs. Turned great, had some drag as it should. Thanks for all of your input. Looks like it' all coming apart to reevaluate...ugh! Rather be done right though
     
  4. Pontiac455

    Pontiac455 Master Mechanic

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    The Master Housing Dimension (MHD) is the distance between the axle centerline and the back of the pinion head. This equals Pinion Head Thickness + Pinion Depth. Since your factory gears were installed using the MHD method from the factory, you know that your pinion depth was properly setup with the correct pinion shim. Since we are changing the pinion, we must now calculate the correct pinion shim thickness. For an example, if Pinion Head Thickness was 1.781 and the shim was .019” thick, doing the math: (4.415-1.781=pinion depth of 2.634) The .019” shim was used to reach that pinion depth of 2.634. If our new pinion head is now 1.770” thick, doing the math: (4.415-1.770=2.645 pinion depth). Since the difference in pinion thickness is .011 less on the new gear, we must ADD .011 to the existing .019 shim to get the correct pinion depth. This leaves us with a .030 shim for the new thinner pinion gear. If the new gear was 1.792, .011” thicker than the old gear, we would subtract .011 from .019 and use a .008” thick pinion shim. Using this method, I have double checked the MHD with my pinion depth checker and found it within .001” of my calculations on both installs. This is the easiest way to do it, and will save a lot of time in installing, measuring, disassembling, and changing shims; not to mention re-installing and measuring all over again.
     
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  5. Pontiac455

    Pontiac455 Master Mechanic

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    The crush sleeve is for bearing pre load only. It has nothing to do with pinion depth. I only install the crush sleeve during final assembly.
     
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  6. Bonnewagon

    Bonnewagon Geezer

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    Pontiac455 I like your method but I am confused. What does the 4.415 represent? Is that a constant? Is the pinion depth of 2.634 a constant? If the 1.781 is the pinion thickness, where is the .019 in the formula? 1.781 plus .019 is 1.80, 1.770 plus .030 is 1.80, and 1.792 plus .008 is 1.80- is pinion gear plus shim thickness of 1.80 what we should be seeking always? Where is that in the formula? Pardon my ignorance but if there is a formula to get the shim thickness I want to learn about it.
     
  7. Rocket Powered

    Rocket Powered Not-quite-so-new-guy

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    After much thinking I forgot to mention this. During the several times of assembling the rearend to check pinion depth the results as followed. I first used the stock .032" pinion shim. Read it should be close. Set preload, checked pattern, it was darn near hitting the root. Next I tried .022" shim. This time pattern was a little further away from the root. Then I tried .010" shim. A little better. I removed that shim, didn't install a shim. Pattern was a little better toward the top of the gear. No shims is what I have pictured in my post. If I add more shims, pattern goes more toward the root. So I question, is this the best it' gonna get? Nothing stock in the rearend at all other than bearings and races. Carrier preload is tight as it should. Diff won't just "fall" out. Idk...had that thing together and apart at least 7 times. I' m a perfectionist
     
  8. pontiacgp

    pontiacgp Canadian Prime Minister

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    If you don't crush the sleeve enough the pinion will sit too deep to get a good pattern and the bearings will not be seated. I have seen a first time builder make that mistake. In this case I have not seen what is being done so I'm just throwing my 2 cents but I have never seen a pinion sitting too deep when there is no shims installed. Perhaps the bearing race isn't seated
     
  9. Rocket Powered

    Rocket Powered Not-quite-so-new-guy

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    Also forgot to mention, during all assemassembly and disassembled the crush sleeve was never used. Pattern looks the same with or without the sleeve. Pattern in pics is with sleeve installed
     
  10. pontiacgp

    pontiacgp Canadian Prime Minister

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    I would send the pictures to Summit and explain to them how you did your set up and see what they say. I think the gears will have to be returned. If this is the set you got I would not buy a no name set of gears from Summit or anybody. .

    https://www.summitracing.com/int/parts/sum-741001/overview/
     
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