Clunky 31. Prop, diff or both?! | The Z Club of Great Britain
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Clunky 31. Prop, diff or both?!

Discussion in 'Z31 (300ZX)' started by zx-mikey, Jul 26, 2016.

  1. zx-mikey

    zx-mikey Forum User

    I owned a Z32 last year and when purchased, the offside rear alloy was buckled slightly. The centre prop bearing was ruined and the prop caused a slight wobble.
    All in all this caused some nasty vibrations. Eventually I solved 95% of the issues and then went on to sell it. I know that the Z cars can suffer a bit from these issues.

    My Z31 is pretty much factory, the wheels are fine and the prop bearing is original. It looks to be intact.
    What the car currently suffers from is a clunk from gear changes. When releasing the clutch peddle after a gear change, there is a pretty noticeable clunk.
    What movement of the drive train is this? What do I need to replace/look at?
    I want the car to be free from this sort of movement, it spoils the drive…I don’t mind a little vibration but this doesn’t sound great.

  2. Huw

    Z Club Member


    Not that up to speed with the mechanics of your car, but there was a thread on here somewhere for a 280ZX with a worn pin in the R200 diff causing a clunking noise. YouTube vid link:

    There are probably lots of other causes of 'clunking' however.


    Last edited by a moderator: Jul 26, 2016
  3. jonbills

    ZClub Administrator
    Staff Member Moderator

    Failure of that pin causes a rhythmic recurring clunk (more a tock-tock-tock imo).
    there are many other causes of clunks, like play in drive shaft, propshaft, bearings in the diff, movement in diff mounts etc. Not easy to diagnose.
    A small(ish) clunk seems to be a very common feature of r180/r200 diffs.
  4. zx-mikey

    zx-mikey Forum User

    Hmm, that certainly looks like the kind of movement in my prop shaft.
    Albeit I haven’t taken off the diff cover, it appears from a quick inspection this could be it. Would this be a possible replacement pin or is this a new diff?!
  5. jonbills

    ZClub Administrator
    Staff Member Moderator

    If it's as far gone as the one in that video, it's a new diff. Before it gets to that stage, the spider carrier shaft (that you can see moving) actually moves up and down and knocks on the ring gear before it starts eating through the diff carrier. if you catch it at that point, you can just replace the roll pin that locates the spider shaft. I think you can probably even do that through the diff inspection cover (although I did mine with the diff out and after I disassembled it)
  6. zx-mikey

    zx-mikey Forum User

    Thanks for the feedback. Now where would I go to find any replacement diff parts for my Z?

    It’s an ’84, manual, turbo.
  7. jonbills

    ZClub Administrator
    Staff Member Moderator

    I think Mike Feeney (Mr.F on here) can supply most parts.
    First step, get that inspection cover off and see if there's wear in the carrier around the spider gear shaft, or whether the shaft moves up and down in the carrier. That spider shaft should be solidly located, no motion in any direction.
  8. jonbills

    ZClub Administrator
    Staff Member Moderator

    the Z32 has an R200 short nose I think, which all have 4 spider gears on 2 shafts and is much less susceptible to failure of the roll pin.
    So I think it's not v likely it is this - but easy enough to look and check.
  9. zx-mikey

    zx-mikey Forum User

    Appreciate it Jon, thanks. I’ll take a look when I can get something ordered. Let’s hope it’s not destroyed! :eek:
  10. zx-mikey

    zx-mikey Forum User

    Sorry for the daft question but how do I find out which diff is on my car?
  11. Mr.F

    Mr.F Inactive

    All UK Z31s have the long nose R200. Ratio will be 3.7:1 for NA and 3.545:1 for turbo. Other markets and models will vary...
  12. jonbills

    ZClub Administrator
    Staff Member Moderator

    Oh yeah, I misread the original post. Z31 not Z32!
    I have a Z31 r200 in my car. (3.36:1 - who knows what that was from?)
    Still, they have 4 spider gears/2 pinions so less likely to have that pinion pin failure shown in the youtube clip. (Thats what I've read anyway!)
  13. Northerner

    Z Club Member

    H'mm interesting thread as I have a similar knock.
  14. CrashCourse

    CrashCourse Active Forum User

    As do I, I had just put it down to general wear and tear of the drivetrain components....
  15. zx-mikey

    zx-mikey Forum User

    No problem Jon, appreciate the input. I should know more by end of play today, I'm going to see a guy who rebuilds old Ford diffs, he should shed some light into what I need to replace.

    Thanks for clearing that up Mr.F…mine is certainly a UK turbo manual, so this helps if I need to replace the whole thing.

    What would you recommend?

    Ah! Well I am starting to wonder what all the fuss is about these cars. You see, I like driving, and ever since stepping into the realms of classic Z’s…nothing but vibrational issues and knocks. Something I never suffered in a short stint of German rear wheel cars. I know everything can be repaired but some of the same design flaws that are in my ’84 Z are seen again in the Z32. To be fair to the Japanese, it looks better than a BMW for example but it’s just shame they never built them to last.

    I’ll report back with my findings from today’s trip.

    Thanks guys
  16. mrM

    Z Club Member

    i have read all the road tests from back in 84 /85 and almost all talk about vibration,slop snatch in the drivetrain if it was in there on new cars its only going to get worse when wear sets in, car too has slack in the diff when i turn the prop
  17. Big Supes

    Big Supes Forum User

    My car has a horrendous knocking sound coming from the rear of the car if you change gears without any consideration. I'm looking forward to getting underneath it and investigating.
  18. Peter Bartlett

    Peter Bartlett
    Z Club Member

    My 208ZX 1982 has a lot of play, not too sure if it is the diff or the CV joints, have had no time to investigate, when cold it is interesting to say the least trying not to judder the car on take off, with the fuel injection fighting the play in the rear drive train. Who stocks the CV joints? on another note the rear springs seem to be sagging, would like to raise the back a bit or lower the front, any ideas.
  19. Huw

    Z Club Member

    Hi Peter

    Mike Feeney (MJP Eastern Autos) can help you with the springs. As to the other problem you have, it sounds more likely you have a clutch issue that diff or CV problem from the way you are describing it.


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