rear end whine..

Discussion in 'Transmission & Driveline Topics' started by 71RS6SPD, Oct 7, 2017.

  1. 71RS6SPD

    71RS6SPD Veteran Member

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    Nov 14, 2016
    So my 71 is finally back on the road after 38 years. In the 80's - I bought new 4.10 gears and a used gm posi unit.I had it professionally installed into the original rear end back then. Before I drove it - I put fresh gear oil and additive in. After 800 miles (yesterday) there is a whine coming from the from the drive line that gets louder with speed and throttle. It sure sounds like the ring and pinion but it may be the outer axle bearings. I do think they were replaced but i'm not positive.

    I bought some prussian blue, opened it up and checked the gear mesh pattern. Both sides look good. Centered between the face and flank (top and bottom).

    After inspection, there is quite a bit of play in the small spider gears - up/down 3/16". These do not turn when going straight so I doubt they can cause the whine.

    Could bad outer axle bearings make noise only under acceleration? It gets loud over 50 mph. There is also a slight noise on decel. I think its coming from the rear, I hope it's not the trans tail shaft bearing. Going to put it back together now as the ring and pinion seem OK. I need more test rides to diagnose noise.

    Just went for another ride.. i'm bummin' I think its the transmission. Maybe the tail shaft bearing? Cornering has no effect on the noise at all. Off throttle - quiet. slightly on the gas = loud gear whine. The gear I am in has no effect - noise is all drive shaft (and back) speed related. I checked the u-joints and they seem fine and are new last month.

    It's a BW t56 from a 94 Camaro that was supposed to be low miles (purchased in the late 90's). I'm going to check the fluid but I did recently and it's not leaking.

    Possible a tail shaft bearing in the trans?
     
    Last edited: Oct 7, 2017
  2. 71RS6SPD

    71RS6SPD Veteran Member

    116
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    Nov 14, 2016
    So after a little research - there is no bearing.. its a bushing.. even a worn one probably won't make noise. I am lost... need to check drive shaft again..
     
  3. SRGN

    SRGN Veteran Member

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    Feb 20, 2009
    Central NJ
    If the pattern is good and backlash is good, check the preload on the pinion.
     
  4. Twisted_Metal

    Twisted_Metal Moderator Staff Member Lifetime Gold Member

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    Feb 26, 2004
    Bloomington, MN
    Was a new pinion nut used?
    It could have backed off a bit.
     
  5. 71RS6SPD

    71RS6SPD Veteran Member

    116
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    Nov 14, 2016
    will check the pinion nut. thanks. How should I hold the yoke while checking the nut? Is an e-brake enough? prob not mine... lol..
     
  6. tom3

    tom3 Veteran Member

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    ohio
    With a four speed the transmission is locked straight through in fourth gear, no gears involved so there could be no whine from that. I'd check that pinion shaft play, trans in neutral, no load on drive train. Try to move the rear end yoke back and fourth, up and down, etc. Maybe some play? But some rear gears just make noise, seems like Zoom gears used to be noisy back in the day. Might drain lube and look for metalflake type particles, a bearing going south there.
     
  7. 71RS6SPD

    71RS6SPD Veteran Member

    116
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    Nov 14, 2016
    Diff oil was clean and there was very little metal on the magnetic plug. I also drained, cleaned and checked the bottom of the pumpkin. No metal.
    The noise is there in any gear if I am going fast enough and does not change with engine rpm.. only shaft rpm. Sure does sound like a pinion issue. Going to get it back up on the stands tonight and pull drive shaft and check pinion for play and nut is tight. If bearing preload is low - can I increase while axles are in?
     
  8. SRGN

    SRGN Veteran Member

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    Feb 20, 2009
    Central NJ
    You can do it with the axles installed. Sometimes this happens when a new crush collar isn't fully crushed, hopefully if preload is the issue it was caught before it wore a pattern into the gears. There may not be enough preload on the carrier bearings as well. With the axles out, if you remove the carrier bearing saddles, the carrier should not fall out with no resistance. It should take a little effort to get it to dislodge. If it stays in with the saddles out, I'd leave it alone. If it doesn't stay in, I'd set up the gears again. If the noise is the bearings, you can silence it. If its in the gears you can either live with it or replace the gears. Either way I'd prefer to know for sure.
     
  9. 71RS6SPD

    71RS6SPD Veteran Member

    116
    4
    Nov 14, 2016
    It's up in the air... again - wish I had a air/hyd jack! I checked the pinion and it feels tight - no movement at all. I did check the backlash when the diff was open and it was fine. I do find a little play in the trans out put shaft/slip yoke but this is prob normal. Guess I will check trans fluid level just to be sure. I am tempted to run it on the stands with ebrake resistance but I think I will bring it to a shop with a lift on Monday as it needs to at speed for it to get loud. Should be able to determine/confirm the source of the noise.
     
  10. 71RS6SPD

    71RS6SPD Veteran Member

    116
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    Nov 14, 2016
    I watched a video on the t56 and I saw 2 main shaft bearings plus the tail bushing on the output shaft. it could be these also.
     

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