Gritty/ Sticky Clutch
 

Has anyone experienced a gritty/ sticky feeling clutch that can only be felt during the pedal travel of the clutch? i.e. holding the clutch in one spot does not propagate the vibration, you gotta be moving the pedal.

I notice I feel it the most if I do the following.

Rev up to 5K-6K in first.
Push the clutch in --> during this travel the clutch pedal kinda vibrates or feels like it's rubbing against something. You can definitely feel it through your shoes. It's most obvious near the end towards the floor.

I've searched around and some people suggested pumping the clutch in neutral a bit. It helps, but the feeling doesn't go away.

Engagement point is fine, shifting is fine so it's not causing any mechanical issues, just feels really weird on the pedal. No weird noises or squeaks to report either. Car is at 42000km, started happening around 40000km. Other forums for the Impreza platform say this is somewhat normal, happens often, and goes away over time.

If anyone's had experience or can chime in that'd be great.

I had a lot of different kinds of feelings from the original clutch. Sometimes it would feel a gritty, or give some kind of fluid resistance.

Either way, this continued until I got a new clutch installed, changed the brake/master cylinder fluid, and changed the trans fluid.

Thanks for the feedback, I suspect it's a problem that would go away with a clutch swap down the road.

To add more info, it is RPM dependent. The higher you rev before clutching in/out causes more feedback through the pedal.

OH ........NO!

Not the dreaded TOB raising its ugly head AGAIN ......... !! ......:cry:


humfrz

I thought the TOB issue is more related to creaking noises.
Should also mention in neutral at a stop, pumping the clutch is smooth. Also low RPM shifting is relatively smooth on the pedal, but it's apparent 2.5K plus.

I'm not saying for sure that it's a bad TOB.

The TOB (on newer cars) is always spinning, (@Ultramaroon learnt me that) as long as the engine is running.

The TOB isn't working (pressure applied to it) unless the clutch pedal is depressed.

If the TOB bearing is bad, or is going bad, it usually makes more of a fuss the higher the RPMs, especially if its under load.

You may wish to review recent threads on clutch problems, for more background information.

I'm sure more armchair mechanics will chime in ....... :)


humfrz

I'm not saying for sure that it's a bad TOB.

The TOB is always spinning on these cars, as long as the engine is running ( @Ultramaroon learnt me that).

The TOB isn't working (pressure applied to it) unless the clutch pedal is depressed.

If the TOB bearing is bad, or is going bad, it usually makes more of a fuss the higher the RPMs, especially if its under load.

You may wish to review recent threads on clutch problems, for more background information.

I'm sure more armchair mechanics will chime in ....... :)


humfrz

Do you notice the squeak/crunch when the car is off?

OP, I sometimes have a hint of what you're describing. There's some sort of feature in the design of this TOB that I've read allows for some slop and is supposed to be self-centering. I don't understand it but every once in a while I get a little bit of the rumble in my clutch pedal. :iono:

No squeaking or crunching when the car is off; in fact it's smoothest and quietest when the car is off.

I think something just needs to be lubed up, but not sure what. I'm just hoping driving it like this is alright and not causing excessive wear on anything. I'd take it to the dealer, but I'm sure I'd get a "normal/ cannot replicate" or a "need a $800 deposit to drop the tranny --> oh it has this small hotspot --> abuse --> fork out cash".

http://forums.nasioc.com/forums/show....php?t=2080802

Thread in question, in case anyone is curious.

You should be saying this, because that's what it is. If the noise/issue he was describing happened when the engine was off that'd be different. Mine made the "creeking" noise/feeling originally (before I replaced the TOB) but it did it with the engine both on/off and was due to the lack of lube on places where lube belonged.

"It makes a funny noise only when I push in the clutch pedal and only when the engine is running." Textbook definition of TOB going south.

OP should pay attention to the noise when the car is cold vs warm. Sometimes the bearing will make different noises at different temp. Mine howled when cold, almost silent when warm. My TOB started making odd noises (like honking sometimes) at about 20k.. finally got bad enough for me to replace it at 55k.

Well I took my tranny out and replaced my TOB last weekend. It was shot, it made noise just spinning it by hand and when I looked at the distances of things when bolting the tranny back to the engine I'm pretty confident the TOB does not engage the PP in its resting position. I would need Ultramaroon to definitively prove otherwise because my own eyes did see that as a reality.

Damnit.. I have to elaborate now after looking at the picture I snapped of my tranny when it was out.

The fork that moves the TOB has no return tension, no return spring. The slave cylinder returns when you let your foot off the pedal and it allows fork to return to its resting position. Now here's the fun part. That fully resting position is far enough back that the TOB wouldn't be making contact if the TOB returns all the way back. But there's nothing in place acting upon it to return it all the way back.

So what happens when the lubed shaft the TOB rides back and forth on is no longer lubed and there's friction? When you release the clutch pedal the TOB may not slide back enough to disengage the PP teeth.

The best analogy I can make is your brakes. There's no piston return spring in your calipers but when you lift off the brake pedal, the pads relax enough that they don't drag on your rotor. Anyone have a sticky caliper? What happens?... Pad keeps in contact with the rotor just enough to get really hot or wear out prematurely.

Well, I think next weekend I will go the hardware store and find out how to make my own clutch return spring.

Something like this:
http://i605.photobucket.com/albums/t...ham/spring.jpg

Correct me if I'm wrong, but from what I understand if the TOB was really going bad, wouldn't I feel/ hear the vibrations if I'm holding the pedal at 50% - 100% and then reving in neutral? Since this would cause the TOB to spin.

What's weird for my issue is that you only feel it if you're moving the pedal. For instance, you'll feel if you rev in neutral and pump the clutch, but you won't feel it by hold it at any particular position.

I'm thinking perhaps something to do with the clutch fork due to it being related to the actuation motion. Again, any other inputs are appreciated! I'll give a listen if I can hear anything holding the clutch at certain positions tomorrow.

Well, @Ultramaroon ....... you're up ...... :thumbsup:

@rice_classic I thought the same as you until @Ultramaroon convinced me differently.

It's now my understanding that prior to about 1985, the clutch systems were set up such that the TOB did NOT rotate, until the clutch pedal was pushed down.

Then about the time hydrolytic clutches came along, "they" figured it was better to have the TOB in constant contact with the fingers of the pressure plate (with a pre-load of a few pounds of pressure).

I scrapped this off the Internet (so you just know it's true ...... :D), but it sounded pretty good to me:

"I did a lot of reading on the TOB when I was setting up my clutch. Even found some posts from an engineer who works for a bearing mfr. The throw out bearing used by our cars [ miata ]was designed for constant contact. It is meant to constantly spin. The stress from a bearing going from a standstill to full spin is much harder on the bearing and reduces lifespan. Stock factory setups can last for hundreds of thousands of kms, mine did. Guys setting them up with no pre-load constantly complain of short lifespans. There was a time that no pre-load on the TOB was how it should be setup, that’s why the clutch forks came with springs to make sure the bearing came away from the fingers."



humfrz