Help. Transmission question. why do wheels spin with clutch in--sometimes?
 

So my shifting into 1 and 2 and R has been notchy but inconsistent for a while. The clutch is new and set up per Tilton's instructions-- full release plus a quarter inch of pedal travel.

I can put the car in gear (motor off), jack up the rear, and spin the wheels by hand with the clutch in. I *know* it disengages and the hydraulic system is fine (and <3000 miles old).

When I start the car, rear end jacked up, brakes off, in neutral nothing happens. just idles normally.

When I push in the clutch and put it into gear, nothing happens. For a little while. Then the tranny WHIRRRS and the wheels slowly spin up.

I can stop them with the E brake or brake pedal and the engine doesn't die. It may dip slightly--but hardly at all.

It does it in 1, 2, 3, and R I think.

If I leave it in 1st with the clutch pedal IN, it will randomly cycle through spinning and stopped without any external intervention.

The primary complaint I have is that I have to jerk it into 2nd then 1st to get it into gear about 50% of the time when I'm driving. not impossible but not ideal.

it *feels* like a tranny problem but seems like it could only be caused external to the tranny.

Help.

hah welcome to the club...this happened to me when my clutch wouldn't fully release until i shimmed the PP away, I could slam it into gears, but the rear wheels would spin.....try adjusting the rod on the pedal...make it longer.

Sounds exactly like the clutch is not fully disengaging. Try adjusting the clutch pedal height some more.

lets assume that if i can turn the rear wheels very easily with my hands when the car is in gear and the pedal is in that it does disengage.

Sorry Matt, there's just no way the engine can spin the rear wheels if the clutch were fully disengaged.
Sounds like you have a situation where you have intermittent failure to completely disengage.

could the pilot bearing stick periodically? it's just weird that there would be intermittent drag on the clutch like that.

like why would it stop itself after 5 seconds?

I've seen this on numerous Miatas. It's just a tight tolerance at disengagement. The load is what helps break the friction between the pp and disk.

The clutch pedal doesn't disengage the disk, it disengages the pp - that means the disk is left touching the flywheel and is still stuck on the trans splines. My guess is the friction surface on your disk(s) will eventually wear to the point that this won't happen.

Nothing a few 4K RPM launches won't fix

on some cars dont they use "release springs" to separate the friction surfaces?

I wonder if my shaft isn't lubed enough :cry:

sig material maybe?

Definitely, but if he ever does get his shaft lubed up enough, he still has to deal with this...

Might I suggest some type of prophylactic device?

yeah... sig material... time to replace one y8s quote with another :-)

best suggestion so far.

since you "have to", might as well get someone to shoot it and then post here ;)

AFAIK the clutch disk usually works on the same principal as brake calipers with the pads

http://exmedsupplies.co.uk/acatalog/...med%5B1%5D.jpg

I have the same shit going on over here.

I adjusted the pedal to the max and STILL it doesnt fully disengage, I'm thinking of shimming the slave rod or something.

And I always make the wife lube my shaft, she has experience doing that kinda stuff, wait...What?

I'll figure this out Saturday and report back.

what clutch did you install? matt did you adjust your rod?

I constantly adjust my rod.

srsly tho I readjusted it the other day to Tilton specs. forgot to tighten it though. oops. But it was ok. a little too close to the floor for engagement but considering it was set to the shortest possible length, it worked great. until a block from home. not sure if that was because it was loose or what.

so I lengthened it a little bit but only to remove the excess free play. my top stop was all the way down and I had a mile of free play with full disengagement. I'll test it more tomorrow on the way to work.

Why hasn't anyone said anything about bleeding the clutch, or failing master/slave clutch cylinders?

I also thought the pilot bearing sticking a bit theory sounded plausible.

But I don't know shit.

-Mike

my clutch hydraulic system has had at least a gallon run through it in the last 6 months. I trust it to be bled.

do pilot bearings stick? I checked it when it was out last and it was smooth.

There's no way in hell it's the pilot bearing. That things tiny, just imagine how much torque it would take going through that little 1" bearing to actually spin all the gears in the transmission full of oil, the driveshaft, and the diff full of oil. That bearing just makes a lot of noise when they go out, it won't cause what your describing.

Your clutch disk is rubbing the flywheel or PP. In your case, you have a fancy twin disk setup so whatever the disk touch, they are touching! Your supposed to use some high temp grease on the input shaft so the disk will slide smoothly. Did you? Obviously you have two disk so there's more friction, causing your problems.

FWIW, I let a shop put Centerforce dual friction clutch in my 86' Trooper II (3" lift on 33x12.50's 10 lights, wench, brush guard, Weber conversion, cold A/C, 70 hp...) and they didn't grease the input shaft AT ALL. So my transmission does the same thing your describing. If I pop the clutch out quickly, it will sometimes get the disk off the flywheel. Needs to be taken off and the splines greased. I actually cleaned them with a wire brush and brake parts cleaner so it would be clean when assembled, but the dumbasses didn't grease the shaft, or tighten any bolts, etc.

I can take it apart when I swap motors (some day)

so tell me ... this hasn't been directly answered yet: why is it fine and then after say 30 seconds at a stop light does SOMETHING happen and I feel the clutch start to rub randomly?

You tell me... Did you grease the input shaft of the transmission with high temp grease before installing your disk?

far as I know. I used the same shit I used the first time I put the twins in--they worked fine before.

Seems to me that could be caused by a leaky master or slave piston cylinder. It disengages at first, then slowly re-engages? The piston could be moving slowly due to a leak.

indeed it makes sense. then the effect reverses, the clutch re-dis-engages and the wheels are free again. :)

gremlins!

I think you have a loose nut between the steering wheel and the driver's seat :giggle:
Weirdness...

Try this.

Hell, I dunno. I would assume your master cylinder and slave cylinders are in good shape, properly bled, no air, you bench bled the master cylinder, etc. If all that's good, and pedal adjustment doesn't fix it either, it's time to pull the transmission. I remember you had to extend the rod on the slave cylinder I think? Perhaps the geometry in that area is wrong and the reason you're not getting full disengagement. This is my hypothesis. I assume the clutch assembly wasn't sticking out enough for proper disengagement, so you extended the rod on the slave. Ideally you would have moved the fulcrum and kept the geometry correct and your slave stock. Any way to do that? Sorry, never had my transmission off (yet).

you realise he has a custom dual disc tilton setup?

http://gallery.y8s.com/d/840-2/Dscn1597.jpg

Si. Note I made reference to the custom slave cylinder, and how his clutch assembly didn't stick out as much as normal.

ok so my geometry is preserved. I lengthened the slave rod and shortened the fork pivot to keep the fork at the same angle.

it could be a mild warpage issue--when the disk is cold maybe it rubs and as it rubs it warms up and becomes flat again. lather rinse repeat.

but I doubt it because stone cold the car is not consistently problematic. so who knows. perhaps I hang out with scott too much?

If it is actually pulling you forward, then you have a leak in the master or slave. Have you checked the external condition of either? The slave cannot have an internal leak, so everything for the slave would be "outside the box". The master cylinder can have both an internal and/or external leak. Again, you can see the external leak when you pull the dust boot off, but with an internal leak it is bypassing the seal and going back to the reservoir, feeling like the clutch is being released.

Another question- Why are you holding the clutch for 30 seconds at a time? Not only is that running your clutch release bearing, but it also could be killing your thrust bearing (or bearings, don't know, have not cracked open a mazda engine).

Also on a side note, if you have a dual disc, they normally rattle around with the clutch disengaged? I couldn't stand to have my dual disc rattling at intersections..... made the car sound like a POS between the cam lope and the rattle.

OH it rattles... but it's not that bad.

Not worried about thrust / release bearings. after 80,000 miles, they seem fine.