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Thread: Differential Rebuild - Gear Markings

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    Differential Rebuild - Gear Markings

    I'm currently rebuilding the differential on my 3A. Never done one of these, and would appreciate some help interpreting the gear markings. This is the first cut with original shims and exact Timken replacement bearings except for the pinion head (used a 3188 instead of a 3188s). Pinion pre-load and backlash were in spec at 18 in-lbs and 5-mils respectively.

    Drive
    Drive Gear Marking.JPG
    Drive Gear Marking 2.JPG

    Coast
    Coast Gear Marking.JPG
    Coast Gear Marking 2.JPG

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    Re: Differential Rebuild - Gear Markings

    Your pattern looks great! A used gear will always look different than the patterns you see in the books as they are setting up new gears. I also had some figuring when rebuilding my TR4 diff as one of the pinion bearings changed and the new spacer is a different length, just a adjustment in the preload shims to get it correct and you are good to go.

    A pattern like you show with backlash in spec is perfect.
    Dave

    TR4 CT8097LO

  3. The Following User Says Thank You to HAWAIICJ For This Useful Post:

    Joel M (05-28-2018)

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    Re: Differential Rebuild - Gear Markings

    Thanks Dave, that's good to hear! I wasn't excited about the prospect of adjusting shims umpteen times to get it right. I didn't consider that a used gear marking would look different than a new one. My main concern was that the drive side looked more towards the toe compared to the coast side which appears well centered.

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    Re: Differential Rebuild - Gear Markings

    You may get a clearer picture if you get some High spot blue. A little goes a long way.

    David

    https://www.ebay.com/p/Permatex-8003...3243320&chn=ps

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    Re: Differential Rebuild - Gear Markings

    I actually have some Prussian Blue lying around. I just used the yellow stuff because I thought it might stand out better. Here are the blue gear markings:

    Drive
    Drive Gear Marking Blue.JPG

    Coast
    Coast Gear Marking Blue.JPG

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    Re: Differential Rebuild - Gear Markings

    Looks good as far as I can see.

    David

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    Re: Differential Rebuild - Gear Markings

    Thanks again Dave. Will consider it done.

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    Re: Differential Rebuild - Gear Markings

    I hate to be the dissenting opinion, but I read that the ring is too close to the pinion. The pattern is right up to the inside edge on drive and outside edge in coast. It should pattern about the same place on the tooth in drive and coast. If it were my set Id shim the pumpkin about .002 away from the pinion.
    John

    1955 TR2

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    Re: Differential Rebuild - Gear Markings

    2X on JDC's comment. You have to much contact on the toe, the pattern should be more to the center of tooth.

    https://www.youtube.com/watch?v=dAqAqODmcj4

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    Re: Differential Rebuild - Gear Markings

    Examine the coast side it is centered face to flank and toe to heel, the drive side is centered face to flank and although it is closer to the toe, when loaded the contact will spread across the tooth. A used gear will not have a proper drive pattern due to the loaded wear the tooth has received.

    This is the manual I trust and have used setting up offroad vehicles.

    https://www.yukongear.com/downloads/...structions.pdf
    Dave

    TR4 CT8097LO

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    Re: Differential Rebuild - Gear Markings

    When I read that, I still get that the ring needs to move away from the pinion. I agree the pattern will move under load, but it should never go right to the very edge of a tooth, as it appears to be. There is a bit of interpretation...like I said, “if it were mine”, I would work the pattern over. But, you can always try it and hope it doesn’t whine. If it does whine it will destroy the ring and pinion in short order.
    John

    1955 TR2

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    Re: Differential Rebuild - Gear Markings

    Quote Originally Posted by CJD View Post
    If it does whine it will destroy the ring and pinion in short order.
    This is not always true. "A singing axle is a happy axle." (I used to work at an axle factory.) Many gearsets will live long and productive lives with whine. That being said, if an axle wasn't making noise and suddenly starts to, it's probably toast.
    60 TR3A TS66043

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    Re: Differential Rebuild - Gear Markings

    Truck axle factory? I've had a lot of 1 ton and larger trucks whine straight out of the factory...including big RV's. I've only had one car that whined, and it was toast when I bought it. A new (used) gearset cleared it right up. I take that back...some of my "extreme" gearsets, like 4.90's and 5.20's whined. We could only hear those when coming back down from 1/4 mile runs, though. Never ran one on the street. Most car drivers won't tolerate a whiny rear end.

    Wait...thought of one more. We had a first year Aviator. At the 6 month point I told the dealer that I could hear a subtle axle whine at 30 and 60mph. Being 4wd I asked if it was normal...they replaced the rear end without my even asking for them to! I never heard it again on that car.

    On a couple different diffs that I was having trouble getting the pattern right...I set up a nice little work area in the living room in front of TV and then spent most of a week shimming and checking...until I was happy with the pattern. Then I got married. The wife won't let me bring the diffs in the living room any more. Real bummer.
    John

    1955 TR2

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    Re: Differential Rebuild - Gear Markings

    Here's a quick guide to Differential noises:
    http://www.onallcylinders.com/2012/0...veline-noises/
    DRIVE 'EM IF YOU GOT 'EM

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    Re: Differential Rebuild - Gear Markings

    So I guess I have two options: 1) leave as is, or 2) move the pinion back a few mils to lift the drive side gear marking. If I move the pinion back, do I introduce risk due to being off the previous wear location if the box had been running as currently shown? Just a guess, but it seems like it might be better to match the pattern in which the gear has already experienced wear. I ask because I rebuilt using identical replacement bearings and shims, so I think I should have virtually identical factory setup.

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    Re: Differential Rebuild - Gear Markings

    I agree with your logic, Joel. It is best to run a used set of gears exactly as it was running. But, If you replaced the bearings, then you cannot be sure what the original pattern was, unless you checked it prior to dis-assembly. Bearings are precise assemblies, but tolerances can combine or subtract. The bearing on the back side of the ring takes most of the load, so it will tend to wear faster than the gear side, allowing the pumpkin to move that direction. All little things that may (or may not) result in the position change when the bearings are replaced.
    John

    1955 TR2

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