8-3/4 hard to turn the wheels

Transmission and Drivetrain Tech

  1. 70DusterBob

    70DusterBob Well-Known Member

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    I just had a rebuilt 8-3/4 installed on my Duster. With both wheels off the ground, in neutral, it is pretty hard to turn the rear wheels forward by hand, both of them turn when you turn one, and I know they are spinning things in the transmission so there should be some resistance, but it seems excessive, but what gets me is, it is 2x harder to spin the wheels backwards by hand.

    What's up with that?
     
  2. fklskv

    fklskv Well-Known Member

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    Automatic tran is normal to spin harder one way.
     
  3. 70DusterBob

    70DusterBob Well-Known Member

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    What I can do is disconnect the drive shaft. I need to replace it with a stronger one anyway, that will tell me if it's the rear end or the transmission making it hard to turn.
     
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    • Garethw

      Garethw Mopar. Because rocket science is too easy.

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      Drum brakes? Perhaps they are just adjusted a bit tight.
       
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      • 70DusterBob

        70DusterBob Well-Known Member

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        I thought of that. I adjusted the ER brake cable so it would have some slack in it, then I pulled the wheels and drums. I had a hard time turning them forward just by grabbing two lugs, but I could not turn the axle backwards just trying to twist the axle with the lugs. I will disconnect the driveshaft to see if it gets any easier, probably this evening since it gets hot here quick and I have things to do this morning.
         
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        • Garethw

          Garethw Mopar. Because rocket science is too easy.

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          You might use a length of 2x4 in the studs to help you turn the axle over. Just a thought.
           
        • 70DusterBob

          70DusterBob Well-Known Member

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          Thanks, I will keep that in mind, but hopefully with the driveshaft disconnected it will be relatively easy to spin.
           
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          • cosgig

            cosgig MoBro Inc.

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            Green bearings? If so did you remove the thrust button?
             
          • 70DusterBob

            70DusterBob Well-Known Member

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            I think you mean the thrust bearing. ?? Anyway, I checked with the guy I bought it from, he said that on the later green bearing models you don't need to remove the thrust bearing. But now I wonder if the guy who assembled it took it out thinking they were the earlier model green bearings???? Yikes!

            Have to wait till Monday to find out.
             
          • Jadaharabi

            Jadaharabi FABO Gold Member FABO Gold Member

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            Did he remove the button or spacer in the middle of the sure grip?
             
          • 70DusterBob

            70DusterBob Well-Known Member

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            I am not sure what the thrust button or spacer in the sure grip is. My buddy said the thrust "bearing" does not need to be removed due to the different design of the green bearings. But I can ask the guy who assembled it if he did or not tomorrow. I will get back with you when I find out.

            BTW, what happens if he didn't?
             
          • Jadaharabi

            Jadaharabi FABO Gold Member FABO Gold Member

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            The green type of bearings do away with the axle endplay adjuster. Therefor if the axles hit the button and you tighten them down tight, you are are causing a bind.

            If it still turns hard after you remove the driveshaft, loosen the axle backing plate bolts on one side and see if that frees it up.

            If it does you can cut or grind a few thousands off the end of the axle to gain end play.
             
            Last edited: Aug 9, 2020
          • fklskv

            fklskv Well-Known Member

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            Everyone that has an automatic trans should go outside, jack it up and see that it will turn harder one way then the other.
             
          • 70DusterBob

            70DusterBob Well-Known Member

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            Hey Frisky,

            I can turn the wheels by hand forward, but it isn't easy. And they are 2x as hard to spin backwards by hand. Does that help?
             
          • 70DusterBob

            70DusterBob Well-Known Member

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            Removing the drive shaft should tell me right? If it is still hard to spin I should not drive it, but tow it back to have the shop that assembled it fix it right? Thanks for the explanation. I am learning a lot about differentials.
             
          • fklskv

            fklskv Well-Known Member

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            correct!
             
          • pishta

            pishta I know I'm right....

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            would it not be the other way around as your slipping the sprag.....? Autos are black magic to me.
            The 8.75 pinion bearing preload is only 6-19 in/lbs depending on new or used bearings, and turning the axles does not require that much more without the trans hooked up
             
            Last edited: Aug 9, 2020
          • 70DusterBob

            70DusterBob Well-Known Member

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            Contacted Doctor Diff. He is the one the axles and bearings came from. I have drums, so he said I didn't need to remove the thrust button, but if he did, it is not a problem. Normal to be harder to spin than an 8-1/4, even a lot harder, and 2x as hard to spin backwards. I will contact the shop who assembled it and ask him tomorrow, and pull the shaft to check for ease.

            Thanks
             
          • AJ/FormS

            AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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            What oil did you put in it?
            140 dyno oil is pretty syrupy. I never use that. I use 75W90

            Normal on mine is; I can turn the driveshaft by one hand;(4 speed, and GVod). So, I am spinning everything inside the od box plus the MS in the 4-speed, with the two synchro assemblies, the driveshaft,the SureGrip thru the C&P,and the axles/drums/tires. But at 1/3.55 wheel speed.

            In an automatic; turning the wheels, turns the MS in the trans,plus the planetary assemblies.
            In the other direction, the sprague locks the low drum and then the planets are forced into action, spinning the low drum inside the band.
            I think in one direction the sun shell spins, which then forces the whole front end to spin.
            In any case, all those spinning things do require more power, as already said, in one direction, than in the other.

            IMO, something is wrong, and I think it is seriously bad news.
             
            Last edited: Aug 9, 2020
          • 70DusterBob

            70DusterBob Well-Known Member

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            Hey AJ,

            Even if I remove the drive shaft and it is relatively easy to spin? I will still contact the assembler and ask him if he removed them. I would have to burn a AAA tow to get it to him to check it out. I have already burned 2, you get 4 a year. I think it is too hard to spin personally, but that is a lot of stuff to spin in the trans, then both wheels and axles and suregrip, etc. He has to fix it warranty if he screwed something up. I would rather get it fixed now than blow something up or break something. I drove it 40 miles this way with the ER Cable too tight, burned the shoes clean up. Could it have burned the axle bearings out of grease too? What should I tell the shop to look for?
             
          • cosgig

            cosgig MoBro Inc.

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            no, it is not a bearing, it is a button shaped coin in the middle of the center section that pushed on the drivers side axle when you are adjusting the preload with the passenger side axle adjuster. May not be the problem if Cass has confirmed the contents of the components inside the center. Just throwing it out there!
             
          • AJ/FormS

            AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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            I have never used the green type ball-bearings. So I cannot say.
            With the tapered bearings you would be Ok cuz they run in their own grease, and the load is spread out over the entire face of the race, with several rollers sharing the load at the same time.
            Whereas with ball bearings you are looking at a different picture. If I had to guess; if they were properly greased in the first place, I'd guess they will have survived.
            Since it has to be taken apart for inspection anyway, I would let the installer worry about it.

            But you just provided a huge clue, when you said the brake shoes are cooked.
            Since we are talking about the rears, there are only three ways this can happen;
            1) a too-tight adjustment; be it either the cable or the star-adjusters, or sticking parts
            2) assembled wrong,
            3) the hydraulic pistons not retracting into their bores

            #3 is the wild card because several things can lead to that condition.
            Principally, the fluid might not be returning to the master. This can happen in several ways;
            mechanically, hydraulically, or a super-heated air-pocket.
            Mechanically; we are talking about rust in the wcs, or a brake-pedal not parking at the top of the stroke.
            Hydraulically; it could be a faulty flexhose. They rot from the inside out, and sometimes a piece will partially break free and become a check-valve.
            Or the M/C pushrod can be too long, closing the return ports permanently. If simultaneously your rear brake system has air in it, then that air when heated, can expand and force the shoes out into the drums. Of course this can start out mild, and then become a chain reaction, as the air picks up more and more heat. This can happen without air as well.
            But the whole thing can only happen if the fluid cannot return to the reservoir, and that usually only happens if the C-ports are blocked, either by the piston or rusted up, or the flexhose is rotten, and of course with 40/50 year old lines, they could be the culprits just as well. It could even be a faulty Combination Valve; I have seen the rubber parts in there swollen up bad enough to freeze them in a permanently applied position.
            So,
            before you ship the car back, I would suggest a lil homework is in order. But I think, perhaps unwittingly, you already did it. You reported that the shoes were burned up. You have to fix that, but that is a separate issue. Since you know this, it implies that you took the drums off. And so that particular (#3 above) is no longer valid. So if the axles are still hard to turn with the driveshaft off, then you have isolated the problem to being in the rear-end itself. And lots of guys have given helpful advice as to troubleshooting that.
            One thing that I don't think I saw was a bent housing. Tapered bearings can run loose enough to not be affected by a mildly bent housing. But ball-bearings have no such forgiveness. If they are forced out of alignment, they will squeeze the grease out, and run steel on steel, making plenty of heat. But if your housing is bent enough to cause that, then your installer would surely have noticed it, as he was "hammering" the axles into the tubes.
             
            Last edited: Aug 10, 2020
          • 70DusterBob

            70DusterBob Well-Known Member

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            Good news, so far... The mechanic did say the green button had been removed, and that it is much harder to turn a wheel on an 8-3/4 than a 8-1/4 by hand. So it looks like its okay. I will still probably pop the shaft off to check for ease after the shaft is off. I can only work from 5-6am to 9-10am and from about 8pm on due to the heat here. Seems like Mr Sunshine has been taking steroids or something, but more likely it is radiation cause we don't have an Ozone Layer anymore.

            So yeah, I will go ahead and replace the shoes, and the wheel cylinders too. The guy I got them from said they were brand new 8 years go, so that is long enough for the cups in the wheel cylinders to dry up a bit.

            I am also, per advice from my mechanic, drive to the top of a medium hill, put 'er in neutral and coast down the hill, then apply the brakes. If the noise, that sounds like a strange scraping noise, occurs, then it is the shoes, not the diff.

            Thanks for everyone's help. I appreciate it. I was having the hung jury effect over these two problems.
             
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            • 70DusterBob

              70DusterBob Well-Known Member

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              Thanks for the detailed reply AJ, I posted in here that the ER Cable was too tight and that was the most likely cause of the shoes hanging in the applied position. The shoes look bad, half gone and black semi glossy on the surface, so in 40 miles they were probably barely tight and rubbing, but the shoes, in my opinion are cooked.
               
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