Rolls forward in neutral, locks up rolling backwards??

Transmission and Drivetrain Tech

  1. Righty Tighty

    Righty Tighty Well-Known Member

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    Howdy all, I've run into a situation here with my 71 Scamp. I have a 904, and at the end stages of an engine rebuild. The engine is in and connected to the trans, shifter linkage is disconnected. I have a 7-1/4 open rear.

    My issue is that I'm not able to roll it backwards when it is in neutral. It rolls forward with maybe a little resistance (hard to tell since I'm on a slight incline and I'm just one man pushing a car), but will lock up when I try to roll it backwards. It feels like it is in park when trying to roll backwards. Both wheels move freely when in the air.

    There's no fluid in the transmission currently, and when I had the pan off to change the filter/gasket, I noticed two things. Brass colored glitter, and black chunks of who-knows-what. I attributed the brass glitter to the front bushing that had been worn, since I saw the same glitter at the bottom of the bellhousing when I changed the front seal. But the black chunks? Either way, these might not even be related to the problem at hand.

    It's been suggested that maybe I have a bad sprag or a problem in the differential. Does anyone have any thoughts?
     
  2. TrailBeast

    TrailBeast AKA Mopars4us on Youtube

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    Just to start with some easy diagnostics, take any pressure off the driveshaft and see if the pinion yoke is loose.
    When they are loose it will do what you described because of one direction causing a mis alignment of the pinion and ring gear.

    Also, you said the wheels turn easy.
    An open type rear end will let you turn one tire one way and the other tire will turn the other way at the same time.
    Put one wheel on the ground or block it and see what turning the one in the air does then.
    If the sprag is working at all, one way will be harder than the other.
     
    Last edited: May 21, 2020 at 5:59 PM
    • Agree Agree x 1
    • RustyRatRod

      RustyRatRod Weenie idiot loser. FABO Gold Member

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      I agree 100% with this ^^^^^^^ ....oh and I farted.
       
    • Righty Tighty

      Righty Tighty Well-Known Member

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      We must be on the same fart cycle.
       
    • Righty Tighty

      Righty Tighty Well-Known Member

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      Thanks, I’ll try turning with one wheel in the air. I removed the drive shaft so I could roll it where I needed it, so next day off I’ll put it back in and try that. I did have both wheels off the ground earlier and checked the pinion yoke, it was snug. Couldn’t move it at all.
       
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      • Righty Tighty

        Righty Tighty Well-Known Member

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        Okay, just throwing this out there. WHAT IF I’m not actually in neutral, but in reverse or drive? Would the car still roll with the e-brake off? I remember pushing the car and it didn’t exactly roll easily, but it did roll. And IF it’s in drive, would the sprag clutch prevent it from rolling backwards?
         
      • CudaFactHackJob

        CudaFactHackJob FABO Gold Member FABO Gold Member

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        When the motor is off, you only have Park...and then everything else.
         
      • Bulldozer

        Bulldozer Well-Known Member

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        take the rod off the gear selector lever on the trans , push the lever towards the back of the car , then two clicks forward , that will give you nuetral on the trans. now see what happens.
         
      • Righty Tighty

        Righty Tighty Well-Known Member

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        I’m not quite sure I follow.

        That’s what I thought I did, but today I started thinking about it, and pulling forward from park, it almost feels like a softer click before hitting the first real click. Then all the other clicks are solid. So what I did to double check yesterday when putting it in neutral, was go backwards from 1st.

        I think I’m gonna put the transmission issue on the back burner until the engine is running, let some trans fluid flow throughout, then see how it behaves.
         
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        • mbaird

          mbaird mbaird FABO Gold Member

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          Did it roll freely before engine / trany install?
          Did you change anything else ? Wheels ? Etc ...
           
        • Righty Tighty

          Righty Tighty Well-Known Member

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          No, it didn’t. I had no problems with the tranny when it was running, pulled the engine and rolled it around a few times. Pushed it into my driveway for the last time before dropping the motor, and had problems shifting into park. Driveway has a slight incline.

          Then when the time came to push it into the garage to drop the motor, couldn’t shift into neutral. Eventually I thought I had freed a stuck park pawl and was able to BARELY spin one wheel with all of my might. I pushed it into the garage with my truck, and it was doable, but seemed harder than it should’ve been using my truck.

          The only work I did to the tranny was replace the front pump and torque converter. Nothing has been done to the differential, only work I did to the rear was bleed the brakes.
           
        • CudaFactHackJob

          CudaFactHackJob FABO Gold Member FABO Gold Member

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          It could be a band tightened down completely. Are you saying you replaced the pump?
           
        • Righty Tighty

          Righty Tighty Well-Known Member

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          Yeah, the splines on the input shaft had to be cleaned up, so I pulled it and replaced it. Had a transmission shop do it so it would be perfectly aligned when put back together.
           
        • CudaFactHackJob

          CudaFactHackJob FABO Gold Member FABO Gold Member

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          I think the shop tightened down the front band to adjust it then forgot to back it off and loosen it the correct amount. That would lock the output shaft from turning backwards.
           
        • Righty Tighty

          Righty Tighty Well-Known Member

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          I removed the pump and dropped it off at the shop, then I installed it. The alignment I was referring to is the pump itself, for when they put it back together.
           
        • CudaFactHackJob

          CudaFactHackJob FABO Gold Member FABO Gold Member

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          I think your front band adjustment is way too tight; all the way tight in fact.
           
        • Righty Tighty

          Righty Tighty Well-Known Member

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          I’m ignorant regarding transmissions, is the front band inside the pump?
           
        • CudaFactHackJob

          CudaFactHackJob FABO Gold Member FABO Gold Member

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          Better start with a search on here. You got a ways to go, but it's easy and simple.
           
        • Righty Tighty

          Righty Tighty Well-Known Member

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          What I’m saying is I didn’t think the front band was inside the pump. The pump was the only thing the shop touched, and I haven’t adjusted anything on the trans, so I don’t know how it could be out of adjustment.
           
        • CudaFactHackJob

          CudaFactHackJob FABO Gold Member FABO Gold Member

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          If the front band isn't tightened down all the way then that means that you jammed something together when you installed the pump; causing the direct drum to lock to the case/pump/between the pump and forward drum. Fingers crossed...
           
        • Righty Tighty

          Righty Tighty Well-Known Member

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          Where I'm confused here is that I didn't loosen anything but the pump to remove it. I didn't touch the front band adjustment.
           
        • CudaFactHackJob

          CudaFactHackJob FABO Gold Member FABO Gold Member

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          The usual procedure to r and r the pump is to tighten the band onto the drum to hold everything in place when the pump comes out. But not doing that allows the forward drum and direct drum to flop around. Thrust washers can drop down and rings might not slide back into where they're supposed to go. Clutches aren't lined up anymore sometimes. What was the endplay like when you got the pump back in?
           
        • Righty Tighty

          Righty Tighty Well-Known Member

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          Ah crap. I didn’t know I was supposed to do that. I didn’t check the end play with an indicator, but it was nice and snug. Is there a way confirm the theory of the band being too tight without pulling the transmission?
           
        • SGBARRACUDA

          SGBARRACUDA ROY FABO Gold Member

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          Installing the front pump is kinda tricky. You may have broke a sealing ring and have it bound up. Or like mentioned above the front drum flopped down and clutches were not aligned when you tightened the pump and have it bound up.
           
          Last edited: May 23, 2020 at 8:10 PM
        • CudaFactHackJob

          CudaFactHackJob FABO Gold Member FABO Gold Member

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          Factory recommends max end play .040. Did the input shaft turn by hand?
           
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