Big Thump when engaging or disengaging clutch

[1984AEisback]

Hey there,
I’m new to the forums. This is my second 1984Z. I got another one after having one along time ago. Anyway, it’s only got 60,000 miles on it and when you shift in and out of gear putting a load on and taking a load off of the transmission and drive line, there’s a clunk both engaging and disengaging unless you do the clutch insanely slowly and perfectly - Which is not close to normal driving. I’ve narrowed down that the clunk sound is coming from somewhere underneath the shifter.

we thought it was on the rear of the car. The car now has a new driveshaft, new clutch, new fly wheel, transmission oil changed, new subframe bushings, new differential mount/insulator all done professionally by a mechanic that’s very experienced. 

The mechanics aren’t sure what to look at next. I jacked The rear end up to get the wheels off the ground and put it in gear and put the clutch on and off to determine that the sound was coming from somewhere under the shifter (mid area) of the car rather than something at the back. Any ideas? Thank you

[1984AEisback]

Here are the 3 videos I took under the car trying to narrow down the noise: 

(25 seconds) https://drive.google.com/file/d/1AjQ4Kvh4eN__tr288uVKkHLbBUymNt8B/view?usp=sharing

(31 seconds) https://drive.google.com/file/d/1_22FuTzPmCNFyJcUcdT6q7TAR0_lbtb0/view?usp=sharing

This one points to the sound as best as I can tell. 

(24 seconds) https://drive.google.com/file/d/18otKlGipECdSjlBNsbwYzFvELL9bxu4H/view?usp=sharing

[Mayolives]

Did you take a close look at the old gear oil that was drained from the gear box?  Was any metal visible in the drain pan? Have you checked the half shafts for play in their u-joints?  

[1984AEisback]

Thanks for helping. We did drain it and there was nominal small shavings according to my mechanic but nothing that he thought was unusual. I am not sure if they’ve checked for play in the half shafts. We will check that. Thank you

[bunkhouse]

15 hours ago, 1984AEisback said:

Hey there,
I’m new to the forums. This is my second 1984Z. I got another one after having one along time ago. Anyway, it’s only got 60,000 miles on it and when you shift in and out of gear putting a load on and taking a load off of the transmission and drive line, there’s a clunk both engaging and disengaging unless you do the clutch insanely slowly and perfectly - Which is not close to normal driving. I’ve narrowed down that the clunk sound is coming from somewhere underneath the shifter.

we thought it was on the rear of the car. The car now has a new driveshaft, new clutch, new fly wheel, transmission oil changed, new subframe bushings, new differential mount/insulator all done professionally by a mechanic that’s very experienced. 

The mechanics aren’t sure what to look at next. I jacked The rear end up to get the wheels off the ground and put it in gear and put the clutch on and off to determine that the sound was coming from somewhere under the shifter (mid area) of the car rather than something at the back. Any ideas? Thank you

 I use a 3'-4' piece of garden hose as a stethoscope. You'll be able to poke it into tight areas while holding it to one ear and pinpoint the sound. I noticed the transmission twitching in unison with the click clack noise. Be sure to check that for the source of the problem.

[1984AEisback]

Thanks!! I’ll try that too

[silverado22c]

Buy a cheap mechanic's stethoscope from Harbor Freight or similar place, only $5.

 

You can hear the gears grinding after engaging gear, that low grind.  The clunk is probably something to do with the syncros, gears or something else internal to the transmission.  I don't have any personal knowledge on these transmissions, just your video pointing to most likely the transmission.  Maybe a gear shaft bearing is worn, not allowing gears to be properly meshed.