Z32 Rear End(?) Clunk - Tearing my hair out

Discussion in 'Technical' started by Boorkus, Jun 30, 2020.

  1. Boorkus

    Boorkus Member

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    I have a manual 1989 Z32 2+2 TT, and have done some major work to the car since purchasing it 4 years ago...
    When I first bought the car, it had a clunk which was obviously the engine mounts, they were torn in half. Replaced the motor and the engine mounts at the same time, just some generic Mackay rubber mounts. Replaced the trans mount with a Nismo one. Also an Xtreme cushion button clutch at the same time.

    I still have a driveline clunk, which presents itself a single loud clunk from the rear when driving when I push the throttle and the driveline torques up under acceleration, and another clunk if I let off the throttle again. Does this in any gear at any speed while driving. Does it when wheels are in the air, although much easier to make clunk with wheels in the air. I have tried:
    • Energy Suspension subframe and diff mounts
    • Brand new OEM centre carrier bearing
    • Checked driveshaft u-joints, they are nice and tight and smooth
    • CV axles regreased (does not confirm whether they are good or not though)
    • Checked wheel hubs, zero play in outer hub splines to CV axles. Packed splines with grease too.
    • Replaced manual trans.
    • Wheel bearings have zero play and spin smooth
    With the car up in the air and handbrake on, I can rotate the driveshaft by hand maybe 1/8 - 1/4 of a turn and clunk the driveshaft/diff/axles back and forth and this makes the same sounding clunk as I've been hearing - from a few other ancient forum threads I have gathered this axial play might be normal and not necesserily the cause of my clunk.

    I've also noticed there is a tiny bit of wiggle in the output hub splines in the diff output flanges - not sure if this is normal or not, but I gather it probably is, I have two diffs here that both feel the same. My only guess left at this point is maybe trying some new axles but where the f*ck would you even find those these days?

    So I'm at a loss trying to find the source of this stupid clunk, any suggestions or pointers would be great.
     
  2. ivan129

    ivan129 Member

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    Does sound like back lash in the diff.
     
    geron likes this.
  3. Martin Williams

    Martin Williams Well-Known Member

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    It certainly sounds like diff back lash. You dont say what you have done to diff, oil change, type of oil, any adjustments to clearances etc. The car is 30 years old and you dont say what mileage it has done but there has to be wear. You could take your spare diff to driveline specialist and have it set-up, then you have a known good one you can change for existing.
     
  4. IB

    IB ?????

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    That amount of play when rotating the driveshaft seems excessive, far more than I've noticed. You say you have two diffs, have you tried both diffs in the car?
     
  5. rob260

    rob260 Moderator Staff Member

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    The Nismo trans mount FYI will cause the tailshaft to be misaligned as it is not a Z32 mount. I'm not suggesting that is causing the issue, but it may not be helping you to eliminate potential causes.
     
  6. ryzan

    ryzan Black Mesa? Fat chance...

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    Diff backlash
     
  7. Boorkus

    Boorkus Member

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    Updated information, here is a video of me turning the driveshaft by hand. It was split at the centre carrier bearing and I was holding it up with my hand and rotating it back and forth:

    Car has done 140k kms. Diff is the original R230V V-LSD with Cusco oil, 80W-90 API GL-5.

    This is the trans mount I installed, and it measured identical to my old OEM one: https://conceptzperformance.com/nis...on-mount-nissan-300zx-180sx-240sx_p_23920.php
     
  8. rob260

    rob260 Moderator Staff Member

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    Trans mount looks like the old one yes but actually puts the trans at a different height, hence the misalignment. As I said that’s not the cause of your issue, just pointing out that it’s not helping. Nismo don’t make a trans mount for 300zx although that hasn’t stopped retailers flogging them off as an upgrade.

    Looks like your diff needs an overhaul.
     
  9. beaver

    beaver southern zeds

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    Looks like your diff needs an overhaul. agree with that, and possibly a one piece tail shaft. I replaced the engine mounts and gearbox mount on my car and reinstalled the two piece tailshaft, even though the two piece shaft had never had any vibration before, after the new mounts went in, it vibrated like a piss-o on a cold morning, mating marks were lined up, nothing helped. Not saying this will happen to you, you may get lucky...
     
  10. Boorkus

    Boorkus Member

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    The diff whines like a bus on the highway too, I reckon I'm up for a diff rebuild... Yay fun times. I might try the other diff I have in the meantime, although it's got an OS Giken 1.5 way LSD in it so it might be even noisier
     
  11. geron

    geron National Petroleum Equipm

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