1st/Reverse vibration + over run gear lash noise

I run a turbo MX5 with a similar clutch. I get a slight judder occasionally but nothing as extreme as you. The gearbox backlash/wine would point me in that direction. 5 or 6 speed?

Not sure if I'm clutching at straws here.


Noticed that the drivers side mount isn't square in the bracket so I might pull it off to have a look.

The mount is a Mazdaspeed item, not overly old. 

Passenger side is dead centre. Given that the hole in the bracket is dead centre along with the threads on the mounts, perhaps the mount has warped or something

As 5 speeds are pretty cheap, is it worth trying another?

Mark, hopefully I'm not trying to teach you something about eggs here

'race' clutches can be a little 'grabby', as soon as a cerametalic lining is used then don't expect oem type characteristics although with gentle 'running-in' the clutch & flywheel can match surfaces for a better 'slip' action.

And (I'm guessing) the centre-plate is sprung? these springs act as a damper when taking-up drive & heavy-duty clutches can have harder damper springs

one possibility is the clutch centre plate was assembled incorrectly & the damper-springs are not damping - rare but can happen...

overly hard bushings can give judder as theres less absorbsion...

your gearbox, is it a 'known' quantity or fitted at the same time as the clutch & diff?

maybe worth checking backlash & general play in the drivetrain - car in gear with rear jacked-up & handbrake off, turn each wheel looking @ driveshaft to diff then turn the propshaft checking for how much everything turns? also maybe worth trying in neutral to see whole driveline rotating (un-powered then powered?)

the diff, you've had the alloy case fail & the diff 'drop', this could have damaged a driveshaft inner cv joint? interestingly, the driveshaft inner cv joints do not have a bearing where they fit into the diff - just float around inside the oilseal and clip into the diff's gears, possible that theres wear or damage in the diff but this is harder to see (floppy driveshaft in diff??)

probably more but this has taken ages to type....

 

christ! weren't you taught about using anyone's name in vain


those mounts from mx5partsni look awfully similar to those available in the US


but I guess they're not made by the sampe people

as to mounts, they're a similar setup to the mk1 & mk2 Escort 'World-cup' engine mounts dating back ~50 years so no new tec. - guessing theres no patent left either?
I still have not made some for my car even though I've got parts leftover from the Nove & Astra mounts I made in a past life



even free



I'd consider this....

Rich.

Cheers Zed, some great points there. I did do some further poking around and got a video to share, something really odd is happening. I did read your post as I was tinkering and checked out each element for play etc, shafts and so forth, nothing seems untoward. Drive shafts spin perfectly central, minimal side to side play but as they should have. Everything is tight and nothing is no centralised. However, read on..

Dadbif, I did check those out and there just seems to be no play what so ever.


So I did more investigation, car up in the air with myself under it. A helper sat in the car, 1st gear, quickly engaging and disengaging the clutch.. Metallic banging/knocking noise every time clutch engaged.

While under the car, I followed the noise and although quite hard to pin down, it seems to be toward the gearbox/front of prop area. A knocking, metal on metal, I'll try and get the video here shortly. What I was surprised to see, was the PPF flexing and I think it is the PPF knocking the box, the video does make it seem like the proper is hitting the box but I have enough space to gets fingers in between so it isn't flexing that much and there are not contact marks.

The diff remains solid, doesn't move but the engine has some movement. Not a lot but it does move/shake a few mm when engaging clutch which I think is transferring to the ppf and making it bow/wobble. I didn't get around to removing the mounts as it got too late/dark but my suspicions are that they may be too soft/broken for the IL motorsport diff mounts. Perhaps the mounts deformed/broke while I had the car sitting on stands for over a year with the engine pivoted back while the ppf wasn't fitted.

I was also thinking, maybe the ppf is bent but it does bolt in place perfectly fine, I had no issue fitting the 5 bolts and I even removed and refitted them last night.

When going for a drive later, if I applied heavy throttle and then let off, there was slack, the uptake isn't quite immediate, as if the drivetrain has to take up the slack and then it goes, same goes for when I let off at high rpm's, there is a wobble in the drivetrain and you feel the car settle as it wobbles back and forth, almost like it had suspension from a 7 series Tailgate McNoIndicate but this isn't suspension related.

So I am left trying to think logically here, the ppf is bridging the diff and the engine, the diff remains still but the engine has some movement, minor but it does move like an engine does, when you rev it or engage clutch. I think that movement is wobbling the ppf.

Or is the input shaft of the drive shaft bent and causing a vibration through the gearbox/ppf..

I just don't know, so I'm hoping this info may help generate some ideas..

Help!

sometimes a fresh pair of eyes & ears can see what you dont, this isn't saying you've missed something - more that you're digging too deep?

also, re. the ppf, it's an (old) aluminium channel-section that was designed for roadcar use with (soft) roadcar bushings @ each end. adding harder bushing @ one end will cause it to 'wind-up' due to different harmonics either end


Rich.

Quick update, wedged pieces of a chopped up exhaust hanger around the drivers side mount, went for a drive and the vibration was noticeably LESS/gone, as the drive went on, when pulling away, vibration was coming back.. Got home, checked and bits of the rubber I stuffed in, had come out, so I'm pretty certain that's it! Will remove the mount to double check but gonna replace for some other style of mounts I've seen made by Direnza.


www.direnza.co.uk/mazda-mx-5-na-nb-mk1-mk2-1-8-2-0-aluminium-engine-torque-mounts?gclid=CjwKCAjw7fuJBhBdEiwA2lLMYRn279jtJRB7JqybY3Vz3aRcFV7WtAzwiLuSa2KJAMkjJ9_4UtxsARoC11oQAvD_BwE