Slipping clutch

[Philip Parker]

Hey all - i’ve been driving my gtx recently and the clutch has started slipping.

It’s essentially a brand new build and the flywheel was resurfaced when the clutch was replaced. Is there an adjustment procedure to ensure that there’s no preload on it?

Philip

[Daniel Roy]

The flywheel is stepped, that is, the clutch cover sits on a level higher than the friction surface. If you resurface the friction surface you must also resurface the step the cover is bolted to to maintain the original height between the 2. The measurement is in the shop manual.

Has this been done?

Dan

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[Joel Sass]

Clutch pedal adjustments can be made under the dash at the clutch pedal. The rod going into the master clutch cylinder is double-nutted. Loosen the nut closest to the firewall (C in image) and adjust the rod. I believe once properly loosened, it can be adjusted by hand. If the clutch is constantly disengaging, you may need to disassemble the rod and clip in order to make adjustments, and reassemble once it's loosened up. If there is no "dead space" in the clutch pedal, check may want to check the pedal adjustment. For the record, I have had a similar issue with the brake master cylinder, where the brake pedal was too tight, and started to apply brakes as the vehicle warmed up. Figuring out why my car gradually became more difficult to drive was weird.

See the following image:

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[Philip Parker]

The problem I seem to be having is that the slave cylinder travel keeps a certain amount of tension on the clutch fork lever. 

The blind holes that are set up for the slave cylinder on the top of the transmission are at such an angle that the rod is crooked in relation to the lever. 

This is a brand new clutch and a resurfaced fly wheel, but I am starting to think that perhaps I have a leak inside the clutch housing. 

The other consideration I am thinking about is that this car has more horsepower than the factory rating. It’s got a full 2 1/2 inch exhaust and I don’t believe for a second after driving it that it’s got only 135 hp. It feels like way more, so I’m wondering if I actually need a different clutch and pressure plate.

Phil 

On Nov 29, 2022, at 2:47 PM, Joel Sass <sass...@gmail.com> wrote:



[Bob Martin]

The rod should NOT be crooked in relation to the lever. It should be along a straight line through the center line of the slave cylinder to the center of the divot in the end of the throwout bearing lever. Did you replace the throwout bearing while you were doing the clutch? 

Bob

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[Philip Parker]

Yep. All the usual suspects were replaced. Here’s a photo of the slave cylinder rod when the clutch is engaged. The angle seems to be preventing full clutch engagement.

On Dec 1, 2022, at 8:35 AM, Bob Martin <wz4...@gmail.com> wrote:



[Bob Martin]

Are you sure the slave cylinder rod is sitting in the right spot in the lever? It looks too inboard to me. Maybe someone with a BF transmission can take a picture for comparison. But, if not seated properly, that would explain your issue.

Bob

[Philip Parker]

Yes, the rod is sitting in the cylinder cup, and the rod itself  actually seems to be the  appropriate length. It’s like the tabs on the cylinder that mount to the transaxle are not right, as it angles the whole cylinder out of whack.  Do I have the wrong part? Can someone else take a photo of theirs and compare with mine? Real head scratcher. 

Phil 

On Dec 1, 2022, at 9:12 AM, Bob Martin <wz4...@gmail.com> wrote:



Are you sure the slave cylinder rod is sitting in the right spot in the lever? It looks too inboard to me. Maybe someone with a BF transmission can take a picture for comparison. But, if not seated properly, that would explain your issue.

Bob

On Thu, Dec 1, 2022 at 9:00 AM Philip Parker <philiptho...@gmail.com> wrote:

Yep. All the usual suspects were replaced. Here’s a photo of the slave cylinder rod when the clutch is engaged. The angle seems to be preventing full clutch engagement.

[Joel Sass]

Whoops, replying to all:

I think I found your problem.

The arm is splined, and can be adjusted by removing the bolt, and aligning the clutch fork's arm.

Here's from the book:

 

Here's from a transmission I have disassembled:

The real question: How is replacing the clutch and pressure plate enough to throw it out of whack so significantly?

[Philip Parker]

That was my first step actually. I did remove the arm and move it a notch further out, however the adjustment was too dramatic to the point where the clutch would not then disengage.

On Dec 1, 2022, at 4:06 PM, Joel Sass <sass...@gmail.com> wrote:



[Philip Parker]

That is the question. What changed? It honestly engages fine and works properly until I hit the gas and the boost comes on. 

It’s an oem clutch and pp. That’s why my hunch is that there is potentially a leak from the transmission. The rear main seal was replaced when I did the engine build but there was no fluid coming out of the transmission. The flywheel was resurfaced by a reputable machine shop. 

I have read that used make a lot more power with exhaust but it could be that much more power? 

On Dec 1, 2022, at 4:18 PM, Philip Parker <philiptho...@gmail.com> wrote:



[Joel Sass]

Hmm. Jeez, I was hoping you could get away without having to pull the transmission. For the record, I do have a pic of the arm and slave in my vehicle:

I suppose the next thing I would look into is the sizing of the throwout bearing, and how it's mounted to the clutch fork. My supposition is that it may be taller than the original, or in some way be constantly putting pressure on the pressure plate's spring. What clutch brand did you go with?

-- Joel

[Joel Sass]

About the setup you have: there is no shot that you are producing enough power to break away a brand new clutch while moving, on boost, unless you are producing a transmission-shattering amount of torque. The vehicle I am taking pics of has a custom turbo manifold, stock turbo with t-bird hot side, larger intercooler, chipped ECU, a 2.5" exhaust to the rear, SPEC lightened flywheel, and a dual force clutch and spring meant for "stage 1", and it never broke torque, regardless of what I was doing. Hole shots, 3rd gear pulls on the freeway, didn't matter. Never slipped.

[Joel Sass]

Taking a look at the manual, there are no shims in place anywhere around the clutch. Further, I don't recall ever working with or around a shim in that location. Was there a shim on your crankshaft behind the flywheel?

On Thu, Dec 1, 2022 at 4:39 PM Philip Parker <philiptho...@gmail.com> wrote:

Yours looks properly aligned. Is there a shim between the flywheel and the crank flange?

On Dec 1, 2022, at 4:37 PM, Joel Sass <sass...@gmail.com> wrote:



[Joel Sass]

Yeah, the splining will be identical, and the shift fork can only go on two ways, but one way would have it pressed through the transmission bell housing, so that's not going to happen. I would suggest you back the arm off one tooth and see how that looks.

On Thu, Dec 1, 2022 at 4:44 PM Philip Parker <philiptho...@gmail.com> wrote:

Ok that’s good to know. It must be the arm then. The fork only goes in one way and I assume the splining it identical. 

On Dec 1, 2022, at 4:42 PM, Joel Sass <sass...@gmail.com> wrote:



[Joel Sass]

Congrats dude. About high idle: I have a lightened flywheel, which leads to a higher idle speed.

I know that if you have the A/C switch on, even if the A/C compressor is not connected, it will cause an idle around ~1000 RPM. When the vehicle is warming up from a cold start, an idle around 2500 is expected until it geta to operating temp, where it should settle down to ~850 rpm. 

Engine idle can be adjusted with a screw on the throttle body, but i would investigate other causes first. Wondering what vacuum you're pulling at idle. Are you running stock intake components?

For the record, if you're experiencing a vacuum leak, you would typically have a low/rough idle with possible stalling because you would have unmetered air entering the intake.

What is your engine idling at once it's warm? 

I 

On Sat, Dec 3, 2022, 15:37 Philip Parker <philiptho...@gmail.com> wrote:

That fixed it. The clutch engages literally right off the floor and feels decent. No more slipping though. 

Have you ever dealt with a high idle? Experience tells me vacuum leak somewhere, however it goes up and down with electrical load. 

On Dec 1, 2022, at 4:50 PM, Joel Sass <sass...@gmail.com> wrote:



[Joel Sass]

A request when communicating in this group: could you please "reply to all" when communicating in this forum? It's helpful for others to reference previous conversations for reference if all communication is publicly searchable. Including 323...@googlegroups.com in your response ensures that this information is available to everyone. 

Most alternators have an integrated voltage regulator. The gtx alternator is no different. If this were a regulation problem, over or under-voltage, you would probably notice the alternator warning light illuminate. I've experienced this with a bad ground and high rpm driving. As I would approach redline, the alternator light would be dim, but visible.

What you are describing for engine idle response is normal operation. The peak charge output for the GTX alternator is 60A at ~2,500 RPM. At idle RPM, the alternator is producing only the amperage required to keep the battery above 12V. As you increase power requirements (blower fan, radiator fan, headlights, etc), the ECU will detect a drop in voltage, and increase idle to keep the battery at a normal voltage. I am not familiar with the idling ranges programmed into the ECU, but I wouldn't be surprised to see a high idle (1200 - 1400) in specific circumstances with high electrical load.

The GTX manual states that idle should be 850 +- 50 rpm with the transmission in neutral, and your foot off the clutch with no electrical load.

--Joel

On Sat, Dec 3, 2022, 21:47 Philip Parker <philiptho...@gmail.com> wrote:

This is great information. Thank you. 

It is very much for electrical related. If I turn on the fan to idle goes up and if I turn on the light cycle goes up. Regular Idle with everything off is around 850. Is there a voltage regulator somewhere on this that may be bad?

On Dec 3, 2022, at 3:51 PM, Joel Sass <sass...@gmail.com> wrote: