NB 6 speed driveline failure diagnosis help please

reggie · Postby **reggie** » Sun Nov 19, 2017 7:06 pm

Hi learned friends,

I need some advice please from those of you more knowledgeable in the ways of MX5's. I have broken something driveline related at Challenge Bathurst today, and am hoping someone may be able to help me pinpoint the problem. I have a normally aspirated 76rwkw nb8b, 4.3:1 torsen, 205/50 semis, car has done 183k km.

I was driving hard out of the chase in 3rd gear, something went clunk, and all the drive to the rear wheels instantly disappeared. I can still select all the gears ok, but it is like the motor and the gearbox are no longer connected - car can be started in gear, and change gears etc without clutch, and no impact on motor or rear wheels. The clutch pedal still has some feel, but it feels different now -not as heavy or as much throw.

I am wondering whether it is an input/output shaft issue? Keen on some thoughts of you wise people out there. Could it be clutch related perhaps? The car has an exedy h/d organic clutch.

Thanks,

Rod (reggie)

speed · Postby **speed** » Sun Nov 19, 2017 7:45 pm

Hi Ron,
With the car in gear and attempting to move does the tailshaft spin?
If yes, you have a diff issue. If no you have a gearbox/clutch issue.
Also, does the car make any strange sounds when attempting to move?

Steve

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reggie · Postby **reggie** » Sun Nov 19, 2017 8:08 pm

Hi Steve,

Thanks for your reply - I started the car in gear, whilst it was on the trailer - no tailshaft movement at all. So that would mean gearbox/clutch.

There is a bit of a new ticking sound, that rises with engine revs (that wasn't there before I am pretty sure), but no grinding or crunching that can be heard. Nothing can be felt through the gear shifter either.

Thanks again.

speed · Postby **speed** » Sun Nov 19, 2017 8:16 pm

Ok, no probs.
For your sake I'm hoping its clutch related.
Maybe someone more experienced than me will chime in.
Best of luck.

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greenMachine · Postby **greenMachine** » Sun Nov 19, 2017 9:37 pm

Bummer!

Hard to diagnose at a distance, but I will keep my fingers crossed that it was just the clutch centre pulling out or something like that. If it was gears I would expect to hear grinding noises, and some of the gears would be working.

6-speeds are not normally a repair proposition, but if it was 'just' an input shaft that may be feasible/cost effective to repair.

Just noticed, 76rwkw :shock:

That shouldn't break anything, not in a million years!

Fingers crossed!

:mrgreen:

Todd77 · Postby **Todd77** » Sun Nov 19, 2017 10:33 pm

Sounds to me that you stripped the spline out of your clutch plate. What brand clutch is it? Ebay from U.K.?

reggie · Postby **reggie** » Mon Nov 20, 2017 6:25 am

Thanks all for your thoughts and help - much appreciated indeed.

The clutch is an exedy h/d organic sprung centre clutch - the clutch centre idea makes a lot of sense. Eithrr way, it’s a pull it all out and have a look.

Thanks again,

Rod

Hoolio · Postby **Hoolio** » Mon Nov 20, 2017 4:28 pm

reggie wrote:…The clutch pedal still has some feel, but it feels different now -not as heavy or as much throw…

This indicates that the clutch plate is now clamping something with greater thickness than it did previously. Most likely the centre of the friction plate has failed and the outer part has move off-centre.

reggie · Postby **reggie** » Mon Nov 20, 2017 7:57 pm

Thanks Hoolio,

Appreciate your help indeed

lightyear · Postby **lightyear** » Tue Nov 21, 2017 7:32 am

I have had this happen twice. Both times it was the clutch.

reggie · Postby **reggie** » Tue Nov 21, 2017 6:52 pm

Thanks lightyear,

Appreciate you sharing your experiences - cheers. I'll update this thread with the results, once it is pulled apart. Thanks again everyone for your help.

Regie · Postby **Regie** » Wed Nov 22, 2017 8:13 pm

Had this happen on my NC

all the clutch material disappeared off the clutch plate itself. could select gears with clutch out and engine running, just no forward movement

id post a photo but photobucket seemed to have misplaced the shot

reggie · Postby **reggie** » Mon Nov 27, 2017 7:47 pm

Evening all,

Well, collectively you were all bang on. Photos tell the picture. The clutch didn't last very well at all - less than 10k km. Plenty of track time, but always dríven sympathetically. Is this an unusual failure?

The next question is what to get to replace it? Any suggestions? I am not sure about a button solid centre plate, as I have a single axle tilta trailer, and being able to slip the clutch a bit while driving it on is very helpful

What would you all recommend as a replacement? Its a track car, but road regoed - dont really drive it on the road at all much anymore.

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