clutch failure diagnostics
 

It's been three weeks since I'd driven the Miata, and finally got a chance to take it out today (70 and no clouds). Got about five miles from the house near the interstate and after jumping on it at 4k in 3rd I couldn't up shift to fourth. No noise, just no shift. Couldn't shift into any gear after that. Car runs and accelerates fine in all gears.

Got it up on stands and check things out. There's no fluid leaks, reservoir is full, the slave has what looks to be the same action as before when it was working, looking up through the fork hole I can see the pp springs moving when the clutch is pressed and it looks like more than adequate motion to disengage the disk. I stuck a magnet down there looking for parts (rivets?) but didn't pick anything up. I'm looking for anything else I can check before pulling the transmission. Any ideas/suggestions? thx-rob

Rob,

I can't help you diagnose your clutch, but can offer you after hours or weekend use of a lift, compressor, and tools--if you can make to to lawrenceville.

Ben

Thanks Ben. Car is way up on stands now, and I've had ten years experience pulling trannies by myself (unforutantely and not preferred). I hope it doesn't come to that, but it seems that's going to be the only way to figure out what's wrong. I hope to have a new garage with a lift sometime next year... which was when I was going to install the 2.2 liter. Wasn't suppose to have any major work on the car between now and then.:vash:

Can you shift into gear with the car off?

turn the car on, disengage the clutch. can you put it in and out of each gear? if you go back into a gear the second time will it grind? could be out of adjustment...

Goes into to gear fine with the engine not running. I drove it home by "leaning" on the stick and matching the revs- it'd pop in. But pressing the clutch had no effect on gear shifting at all. Leaving the traffic light just prior to "getting on it" and it shifted fine. I couldn't tell anything mechanical happened to it- it was just a suprise when it wouldn't go into fourth. The pedal doesn't feel any different either. The resistance begins at the same point- and you can see there's full motion on the slave, and see the pp springs flexing. I might try putting it in gear, engine running, clutch fully pressed, and then holding down the brakes as hard as possible to see if it'll slip. Just wonder if something is wedged in there... like a disk friction pad or piece. It wouldn't take much. That might break it loose.

dude i wish i knew peoples names on here so when I see them on other forums and mailing lists I know who I'm talkin to. hehe

there's a only a small overlap between here and the power list- like you, me and joe perez.

thats probably good. i read enough OT there.

Just an update:

Pulled the slave boot back, no fluid. Check it's action against another and it's at least equal. So I start it up in first, mash the clutch to the floor and then bury the brake while mashing the gas. As the revs rise, I hear a loud PWANG! I can now get it in first and second with some effort. Third, fourth and fifth require double the effort. Reverse is impossible- probably because the clutch isn't fully disengaged.

Now for a twist. The slave is a Miata unit, but the shaft/rod is custom (lengthened) to work with the b2000 bell housing and fork. When I'd originally set this up there was about 1/16" of tolerance between the fork and the rod/shaft end after a good clutch bleeding. When I checked it today the shaft was firmly pushed against the fork, which probably means the t/o bearing was riding on the pp springs all the time. Any theories as to how this might have caused or contributed to the problem?