How to adjust 8-3/4" axle bearing preload?

Brakes, Steering & Suspension

  1. '74 Sport

    '74 Sport Active Member

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    My son Aaron and I just finished putting his Duster's 8-3/4" rearend back together with new everything. This one came from a '69 Charger, so it has the bearing preload adjuster on the passenger side axle.

    I need someone to reply who is very well versed in how this adjuster functions - what it does and how it does it. The axles have way too much end play, so I need to know how to go about making the adjustments.

    I believe it is also supposed to have a clip of some sort under one of the retainer flange bolts that keeps the adjuster locked down. If so, it is missing and I need to know what one looks like (any pics appreciated).

    I assume the end play is measured on the adjustable right side? How does the adjuster do its job? Do I turn it clockwise or counter-clockwise to tighten (remove end play)? What does it have to do with the left side axle end play? What's going on inside the differential?

    The adjuster has alternating tabs turned down towards the axle shaft. The other tabs I guess are left upwards to provide a surface to tap with a punch/drift to rotate the adjuster. Turning it counter-clockwise backs the adjuster outward towards the axle flange; clockwise moves it inward towards the axle tube.

    Am I wanting to back the adjuster out so that the turned-down tabs to make contact with the nearby machined lip on the axle, or does that not have anything to do with removing end play? Or do I want to move it inward (what that does I'm not sure).

    The rearend is off the car sitting on some jack stands. What do I do to check the end play, just pull out on the axle flange with my hands, or do I need pry out on it harder with something?

    Thanks for any help,
    Jerry
     
  2. Gary67

    Gary67 Well-Known Member

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  3. daredevil

    daredevil Well-Known Member

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    im glad i read this. i didnt know about the retainer as i put mine together from parts aquired here and there. i have a couple b axles saved ,i,ll have to go find one to rob. thank yawl for posting
     
  4. '74 Sport

    '74 Sport Active Member

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    Guys, thanks very much for the replies (and offers). I think we now have this rascal beat.
    I'm going to see if I can knock out a simple tab to serve as the locking pawl. If I run into trouble, I'll give you a shout, Neccid.

    Pete, stick with me and you'll learn much - I have lots of questions to resolve. :sSig_thankyou:

    Thanks much,
    Jerry
     
  5. Meep-Meep

    Meep-Meep дворянин

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    The end play spec is .008-".018" if I remember correctly, or like the article says, just a slight movement.

    The ends of the axle shafts but up against a floating spacer like part in the differential, which control the thrust in that direction. If you have a factory 4 pinion sure grip unit there are small thrust buttons that contact the center of the axle shaft end and are held together with a pin. One word of caution if you have this type of sure grip unit. The little pin that holds the buttons together is almost always broken and will not stay with the spider gear cluster when the axle is removed. Upon axle removal the button will get stuck on the axle shaft end with a little film of gear oil and when you pull the axle out it will surely fall off and land into the bottom of the rear end housing as the axle end clears the spline. After you have the axle out you can retrieve the button from the housing by removing the third member :(

    To know what type of sure grip unit you have (assuming you have one) is to look at the wear pattern at the spline end of the axle shaft or down the axle tube into the spline area and note the diameter of the thrust surface. A small shiny wear spot in the middle of the axle indicates the 4 pinion sure grip. If the entire end of the axle is shiny it was used with an open rear end or the later cone type sure grip, which has a large diameter thrust surface. If the small buttons on the 4 pinion sure grip are missing you will never get the end play adjusted. The larger thrust surface setup has no issues with falling out.
     
  6. '74 Sport

    '74 Sport Active Member

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    Nope, not a sure grip, just the plain ol' open gears. We got the adjustment made, now I need to fab a locking tab/pawl. Doesn't look too tough. Once we get the rearend swapped into the Duster and are able to take it for a short test run (still haven't broken-in the newly rebuilt engine), we'll double check the axle end play.

    Thanks again,
    Jerry
     
  7. 62 Dart Convertible

    62 Dart Convertible Well-Known Member

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    Thanks for the info here Meep-Meep!! You have answered all my questions prior to pulling out my third member to investigate the 3/16" axle shaft end float I have found in my car. I suspect the axle shaft thrustspacers are either missing entirely or floating in the bottom of my case (though unlikely as they would surely end up in the mincer...) If they are missing, the problem will be sourcing them here in Australia....
     
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