Doctor diff axle question-

Transmission and Drivetrain Tech

  1. Syleng1

    Syleng1 Karma is real and Life is short... FABO Gold Member

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    So I sent the new to me 8-3/4 abody housing out for a good cleaning before assembly on my 66’. I purchased Doctor Diff BBP axles for stock width and green bearings. When my housing came back the machine shop took out the axle seals from the factory. With the green bearings that are sealed..... are you running additional axle seals or not and don’t have leaks. Doctor Diff says it’s a good thing to use them. But do I have to with sealed green bearings. So again what are you running with these bearings?


    Also, I’m removing a 8-1/4 rear to install the 8-3/4” I know I need to try the fit. Any charts available for yoke to centerline on these two axles? Trying to figure out fingers crossed if I will have to cut driveshaft or not. I thinks it is a 1” difference. 8-3/4” needs less shaft than the 8-1/4”. Anyhow thanks for reading.

    Syleng1
     
  2. my68barracuda

    my68barracuda Well-Known Member

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    I am running Dr Diff axels with the green bearings and like he recommended I installed the axel seals,
    The seals were not difficult to find or to install.
     
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    • str12-340

      str12-340 FABO Gold Member FABO Gold Member

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      You wouldn't want rear end lube in your brakes would you??? That's what the seals seal off
       
    • Syleng1

      Syleng1 Karma is real and Life is short... FABO Gold Member

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      I like my brakes wet - they wear less. Lol!
       
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      • Darter6

        Darter6 Well-Known Member

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        I have run them both ways.IF you do install the seals make sure they are fully seated in the housing as far as they go.The bearing retainer may rub against the seal if not.
        Without, Make sure you housing is in good shape where the "O"ring of the green bearing contacts. I also will put a thin coating of RTV in that area of the housing as it helps lube the "O" ring as it slides into place, also sealing it.My 2 cents.
         
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        • SGBARRACUDA

          SGBARRACUDA ROY FABO Gold Member

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          It’s like the insurance on your car. You hope you don’t need it. But if you do it’s there.
           
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          • MoparMike1974

            MoparMike1974 FABO Gold Member FABO Gold Member

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            • Dartnut

              Dartnut Don't hate me because i'm beautiful

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              If Dr. Diff says to use them, and they are cheap, why would you be over thinking this?
              Just install them and be done with it.
              Cass (Dr. Diff) is an expert on this, so it would be good to follow his recommendations in any case...........
               
              Last edited: Jun 10, 2020
            • MoparLeo

              MoparLeo NRA BENEFACTOR LEVEL LIFE MEMBER FABO Gold Member

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              You might be thinking (mistakenly) that the differential lube is what lubes the axle bearings. The axle bearing was hand greased with a heavy grease and the differential is lubricated with a fluid. The only thing that a Green bearing does is eliminate having to manually grease the outer bearing and adjust end play. So yes you still need a housing seal unless you are going to rely on the new bearing to block any axle lube that may come in contact with the bearing. Why didn't you stay with the much stronger bearing that was originally designed for use in these axle assemblies (sealed bearings were available back then) ? The Green bearing is inferior in strength both in load carrying and side loading. Trucks use the tapered bearing almost exclusively because of their strength and durability.
               
            • Syleng1

              Syleng1 Karma is real and Life is short... FABO Gold Member

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              MoparLeo- I understand how load effect bearings. My question is do I need the additional seals with green bearings? My 72 Demon I swapped to BBP about 8 years ago and removed the seals with moser axles and green bearings and no leaks. I don’t mind ordering them OR using them. I was curious if I really needed them because with today’s delivery times (what was 1 week is now 2 weeks) I’m just excited to swap out my 2:45 8-1/4 to the 3:23sg 8-3/4. I can wait an extra week but I wanted a consensus on what others have had success with. So far every has said do it but not - “I tried to go without them and they leaked.”
              That’s all.
               
            • Syleng1

              Syleng1 Karma is real and Life is short... FABO Gold Member

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              So I’m conclusion- I ordered a set of inner seals and they will be in tomorrow. Napa actually has them but in the locAl warehouse. So I wait until tomorrow am.

              thanks for All the help people!
               
            • str12-340

              str12-340 FABO Gold Member FABO Gold Member

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              I'm sure that this project will make you happy from the first time you hit the gas!!! Have Fun !!!
               
            • Syleng1

              Syleng1 Karma is real and Life is short... FABO Gold Member

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              Thanks! I’m looking fwd to it because the 3.91’s in the 340 4 speed Demon are “sometimes” a bit much. Much Fun! That is.
               
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