Z31 grinding through gears after rebuild

  • #1

    Z31 grinding through gears after rebuild

    Hey, not new to the forums but I have decided to make an account to get some advice on an issue.

    I got my transmission rebuilt from Fitted Garage, located in Sacramento CA. I took it in for a rebuild because the previous owner daily drove this 85 300zx with the gears grinding constantly. I got the car back and it definitely doesn't grind as bad, but it still grinds through 2nd, 5th, and has issues entering reverse sometimes. I got the clutch replaced with an Exedy OE replacement, and the flywheel was also resurfaced before installation.

    Does anyone have any pointers on what to look for to resolve my grinding issue? I've heard rumors from my other friends who own Zs that this is pretty typical in a 300zx transmission. I'm open to any ideas.
    Thank you.
  • #2
    Three different manual transmissions were used on Z31s and two for 85 cars so you might want to specify the type. Have you talked to shop who did the rebuild? What do they say about it?

    What was replaced and what was kept? As far as I've understood, in a rebuild most commonly the bearings are replaced, synchros depending on condition, and gears only if necessary. Perhaps the gears were already too worn from driving it like that for a longer period?
  • #3
    Originally posted by kaur View Post
    Three different manual transmissions were used on Z31s and two for 85 cars so you might want to specify the type. Have you talked to shop who did the rebuild? What do they say about it?

    What was replaced and what was kept? As far as I've understood, in a rebuild most commonly the bearings are replaced, synchros depending on condition, and gears only if necessary. Perhaps the gears were already too worn from driving it like that for a longer period?
    I have the FS5W71C. It is the original transmission just rebuilt. When I picked it up from the shop, the shop owner told me that literally everything was replaced, and so there was not anything kept behind.
  • #4
    My guess would be that if it hasn't been done, the clutch pedal play needs re-adjusted.

    http://xenonzcar.com/z31/FSM/1985/CL.php page CL-3.

    Also, if the slave cylinder push-rod is too short, the throw of the piston in the slave cylinder won't be enough to completely engage the throwout bearing.
    I've purchased slave cylinder kits where I've had to use the old pushrod because the one that came with the new kit was the incorrect length.

    If you suspect this, adjust the clutch pedal first as in the link above, then you can get a steel rod and trim it so it is a few mm longer than the one in there
    round the ends and swap it with the push rod and see if that helps with gear engagement.



    84 AE/Shiro #683/Shiro #820/84 Turbo
  • #5
    Originally posted by Z_Karma View Post
    My guess would be that if it hasn't been done, the clutch pedal play needs re-adjusted.

    http://xenonzcar.com/z31/FSM/1985/CL.php page CL-3.

    Also, if the slave cylinder push-rod is too short, the throw of the piston in the slave cylinder won't be enough to completely engage the throwout bearing.
    I've purchased slave cylinder kits where I've had to use the old pushrod because the one that came with the new kit was the incorrect length.

    If you suspect this, adjust the clutch pedal first as in the link above, then you can get a steel rod and trim it so it is a few mm longer than the one in there
    round the ends and swap it with the push rod and see if that helps with gear engagement.
    Thank you, I'll make sure to look into this soon. Much appreciated.