Project Christine slo Hackensteinberg

[theholycow]

On the way to work today, sudden horrible grinding. Thought I had a catastrophic wheel bearing failure. Jacked car, checked wheels, felt ok. Then I noticed driveshaft's forward U-joint resting on safety bracket. Then I noticed transmission mount failed.

Rigged part of mount back in place sideways with strap and huge zip tie, got a few miles up the road, happened again. Removed safety bracket, let transmission rest on crossmember. Yoke can't escape transmission anyway, it's way too deep.

I guess I'll fix it tonight in the cold and the dark. New mount is only $7 so at least it won't cost much of anything.

[Rope-Pusher]

We're acomin' ta save you Cow-Boy!

[theholycow]

Ok, realistically, not gonna do this in the dark after work when wife's car is available. I'm back to driving the Sunfire this week. Drat.

[theholycow]

For a couple weeks I've been having a little trouble getting into 1/3/5, mostly from neutral (and downshifts to 3). I suspect flex in the hacky DIY half-assed clutch slave cylinder bracket.

Yesterday I noticed that I was revving higher for launches and upshifts and this morning I realized that it is because my clutch is engaging higher in the pedal travel but I hadn't adjusted my clutch foot to match. I'm unable to get it to slip with my foot off the clutch pedal, but does this sound like a worn out clutch? Or, combined with the other symptom, should I be looking at a hydraulic issue?

Maybe today at lunchtime I'll pop the clutch master cylinder cover and see if I'm low on fluid.

[Rope-Pusher]

For a couple weeks I've been having a little trouble getting into 1/3/5, mostly from neutral (and downshifts to 3). I suspect flex in the hacky DIY half-assed clutch slave cylinder bracket.

Yesterday I noticed that I was revving higher for launches and upshifts and this morning I realized that it is because my clutch is engaging higher in the pedal travel but I hadn't adjusted my clutch foot to match. I'm unable to get it to slip with my foot off the clutch pedal, but does this sound like a worn out clutch? Or, combined with the other symptom, should I be looking at a hydraulic issue?

Maybe today at lunchtime I'll pop the clutch master cylinder cover and see if I'm low on fluid.

As the clutch friction disk wears,.....
it gets thinner.
As it gets thinner, the pressure plate moves closer to the flywheel.
As the pressure plate moves closer to the flywheel, the fingers of the diaphragm spring in the clutch cover move back, toward the release bearing.
As the release bearing moves back towards the transmission, the clutch slave cylinder rod and piston move toward the hydraulic fluid port in the clutch slave cylinder.
Normally, as the piston in the clutch slave cylinder moves closer to the port, it pushes more fluid back up the line toward the clutch master cylinder.
As more fluid comes toward the clutch master cylinder, it pushes the piston in the master cylinder back down the cylinder until the hydraulic fluid port is uncovered.
As the hydraulic fluid port in the clutch master cylinder is uncovered, the piston reaches the end of it's travel in the clutch master cylinder and the extra fluid has nowhere to go but out the port and up the reservoir hose to the clutch hydraulic fluid reservoir.
The fact that the extra fluid can move up to the reservoir normally readjusts the system to compensate for the worn clutch friction disk and the pedal travel upstop, downstop, release and engagement points stay the same.
Remember that part about "Normally"?
If something is changing in the release or engagement points, it may mean that the clutch slave cylinder is as close to the hydraulic fluid port as it can get and the load on the clutch release bearing is not being fully released - the preload of the bearing against the diaphragm spring fingers increases and the clutch begins to lose its torque capacity.

So if there is some way that you can adjust the bracket that holds the clutch slave cylinder so that the piston is no longer at the end of it's travel when the clutch pedal is fully released and it may help move the release point at the clutch pedal back closer toward the downstop position.

[theholycow]

I can probably adjust it that way...and honestly that's the opposite of what my gut feeling was telling me, but I wasn't able to think through the entire "the leg bone's connected to the knee bone" song for the hydraulic clutch release system accurately while I was thinking about it on the way in to work today. Thank you. I hope I get a good look at it this weekend.

[theholycow]

I've posted a few times in the past year or so about some clutch symptoms. I've been too lazy to take anything apart.

Lately I've been noticing something I've never noticed before. In neutral, clutch engaged / pedal fully up / not touching the dang thing, I get a "rrrrr" sound similar to straight cut reverse gears or a power steering pump trying really hard. It tracks with RPM and disappears the moment I step on the clutch pedal.

Any guesses? My guess is release bearing.

Could be normal life for this release bearing in this hack application (I feel like there's more pressure on it than there should be at rest), could be prematurely worn by some excessive long-term clutch disengagement I've been doing to work around my other symptoms, could be related to the semi-slipping clutch symptom (bearing not worn out or prematurely worn, but either way with a worn clutch and potentially not enough play it could be under more pressure at rest).

[Rope-Pusher]

Well, If it was low on bearing preload, the bearing may be sliding along the clutch cover diaphragm fingertips. F N it's not noisy as soon as you add some pedal load, that may be the KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK.

[theholycow]

I'm chewing on the idea of switching to a concentric clutch slave cylinder. However, I can't seem to find one with the right bore diameter (let alone could I then guess at hydraulic specifications, collapsed length, and throw). Inner diameter of my release bearing is 1.3775 in (or 1.3779 depending who you ask), which is 35mm. I'll need a concentric slave cylinder that size (or slightly larger will likely be fine).

I would want to find a regular replacement part for another vehicle, not a custom/aftermarket/racing item. Otherwise I could spend a whopping $165 on http://howeracing.com/p-7754-improved-h ... lutch.aspx but for that price I'll stick with my old-school external slave.

[Rope-Pusher]

There is a lot to be said for keeping the slave cylinder out of the bellhousing. Makes hydraulic release system issues easier to diagnose and repair.

Also, the concentric slave needs to mount to the case to hold it in position from tilting or twisting. For OEM replacements, you just bolt to the threaded bosses inside the bellhousing. For do-it-yourselfers,......punt!

[IMBoring25]

...Yeah, replacement of the external slave on the 'Vette, while bad due to the shape of the floorpan, was far better than replacement of the internal slave on the truck. What are you hoping to gain by the change?

[Rope-Pusher]

What are you hoping to gain by the change?

Fickset

[theholycow]

Yeah, those advantages of the external slave have been important to me and I've been a big proponent of them.

However, there are disadvantages. One is the backyard-engineered halfass-fabricated slave mounting bracket that fatigued and cracked. It was repaired but I'm not 100% confident in it, and it has always been insufficiently stiff. Another is proximity of the plastic-cased slave cylinder and plastic hydraulic line to the exhaust manifold. A concentric slave would eliminate those failure points, protect the slave from road debris/salt/etc, and simplify the system by removing the fork/pivot/etc. It's a simpler, more robust system that's less easy to repair but less likely to need repair.

Another disadvantage of external slaves, though not important at this time, would be clearance for headers, which I'll probably never get anyway. I would absolutely require an internal slave if I ever got headers.

Since I'm thinking of taking the transmission down to investigate the symptoms I'm having, I figured now is a good time to deal with that too. Since I'm also hoping to put in a new engine next year (probably won't, but I'm hoping), I figure if it's not optimal then this is a good trial before the next time I drop the transmission anyway.

[Rope-Pusher]

When you have it apart, take a good look, make some measurements, write down some notes...you're going to want to match that CSC travel to the release bearing travel, so there is always some preload and room for diaphragm spring fingers to come "Back" as the clutch disk wears and yet not bottom the CSC in the extended position when you are disengaging the clutch either.

You might need to adjust the position that the CSC sits at to do that, so think how to mount some plate in there at the proper position in the bellhousing to react the thrust of the CSC and also to keep it clocked to a certain position about the input shaft. The bearing isn't 100% efficient, so it will have to react some motion trying to spin it around the shaft.

[theholycow]

In addition to the 899various symptoms I've been ignoring, now it's popping out of 4th gear.

I have a spare transmission and I feel like I ought to slap it in this weekend, the last warm weekend for like 6 months. I'm really not prepared to do the job.