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Lately I've noticed a bit of vibration in the clutch pedal when starting in first gear. Any ideas what that's about?
Greg
Simple vibration could be a lot of things. Potential faults...Transmission input shaft bearing, clutch throw-out bearing wear, wear on the pressure plate fingers, oil/grease contamination on friction surfaces, warped mating surface (heat damage), or damaged clutch disc. If you get chatter/vibration when releasing the clutch to engage the flywheel/pressure plate, it's usually a sign that you have a problem with the flywheel/pressure plate/clutch disc. It's very possible some type of hot spotting or contamination (glazed) is present on the friction surfaces.
If your clutch isn't slipping under load, you're probably safe to continue driving it and just live with the vibration until it's time for a new clutch. My Z had horrible chatter/vibration when I bought it and I discovered while doing the clutch replacement that both the flywheel and pressure plate surfaces were contaminated/glazed badly. At some point those components were overheated due to driver error (riding the clutch or dumping the clutch attempting to do a burnout, money shifting, etc....)
I had the RJM clutch pedal installed by my mechanic and I don't think he installed it correctly and/or had it adjusted properly. First drive after the install and the clutch was engaging immediately after the pedal was barely moved off the floor. In fact, I learned later that the clutch was not disengaging all the way with the pedal all the way to the floor. I drove it a few times with the clutch pedal adjusted this way, and then the day before my appointment with Z1 Motorsports to do the Dyno Tuning I had an incident where I was at a stop light and couldn't get the car into gear. The clutch was not disengaging enough to where I could get it in gear. Finally, after waiting a few minutes and fiddling with it, I did get it in gear and limped home. Austin came over early the next morning and adjusted the clutch pedal and we took it for a spin and even though it was still engaging too early, it seemed to be working ok. I decided to make the 4 hour trip to Z1 to have the tune done. After I got done at Z1 I went to Marietta to test drive a Boxster. As I was leaving to head home after the test drive, a big rain storm hit and in the middle of the rain storm I got stranded at an intersection with the same problem of not being able to get the car into gear. Long story short, I ended up using my annual 'long tow' with AAA to get the car to Elite Auto Repair in Sparta, TN (175 miles) and that's where it sits right now.
I have two issues going on with the clutch. The first being the pedal, which I know is not installed/adjusted correctly. That's what really left me stranded in Marietta. The second issue is the vibration problem. The Tech at Z1 said that even with that vibration I could probably drive the car for a very long time without the clutch actually failing. But I don't like the feel of it and I've decided to have Elite replace all the clutch parts on the car and re-install/re-adjust the RJM clutch pedal.
Greg
Last edited by TN350ZRoadster; Aug 14, 2023 at 09:51 AM.
Vibrations may be due to a defective flywheel. The Z is equipped with dual-mass design(DMF). Google up "problems with DMF", it may give you insight.
Z Speed offers options, good vendor: https://zspeed.com/product-category/...eel-2003-2006/
The steel single mass (19 lbs.) will eliminate the shudder / vibration encountered with a defective DMF, (they go out of balance when worn) and will give you better performance than the 25 lb. stock unit. It also will be much quieter than a lightweight aluminum flywheel.
Kudos for maintaining / upgrading your Z.
Sorry to hear about the troubles with the clutch pedal. Something is definitely not right, I did have to make some minor adjustments after my initial install of the RJM v4 pedal, but I never had the clutch failing to disengage with the pedal fully depressed. When you ordered the pedal from RJM did you go with their HD Clevis fork or did you re-use your stock clevis? As I recall, you also had your mechanic make some adjustments to your OEM master cylinder rod/clevis pedal settings before? I believe you already took care of the fluids, so the clutch hydraulics should be fully bled/flushed with fresh fluid. I'm also assuming your mechanic inspected the master and slave cylinders for any signs of leaks.
As timeltel and you both surmised, you may have an underlying clutch issue. If the vibration issue was always present and has only gotten worse, it is possible the dual mass flywheel is failing or the clutch disk &/or basket. The throw-out bearing could also be toast, even though the mileage is low, the bearing itself is old/original and they are not sealed units. The grease has probably dried out and some rust or corrosion could also be present. I've only witnessed this behavior (clutch failing to disengage) once before on my buddies Z32. He was power-shifting and stressed his clutch disk so much, that the springs in the disk's hub busted out of their cages from the drivetrain shock. This caused the pressure plate fingers to jam and prevent the disk from disengaging with the crank. The tell tale sign was that you could only shift gears on the trans with the engine off. This all happened because he was driving the car hard while bedding in his brake pads with new rotors and seemed to really enjoy hard pulls from 1st to 2nd.
If you care about maintaining the factory drive-ability (comfort), then the zspeed EZ street clutch kit is one of the best choices on the market. I purchased this same kit for my Z, I went with the steel 19lb (18.4 on website) single-mass flywheel. Engagement is very smooth and controllable. Minimal torsional vibration (gearbox chatter) that plagues most aluminum light weight flywheels. I'm extremely happy with it.
Again, I'm terribly sorry to hear about the pedal mod going wrong. I feel somewhat responsible since I recommended it, once setup correctly it really is an amazing improvement. The mistake I made was NOT bleeding my new hydraulic with the OEM pedal BEFORE installing the RJM pedal. Instead I installed everything in 1 shot and attempted to bleed the system with the RJM pedal. This little mistake added a lot more time fiddling with the RJM pedal to bleed the system, only to make more adjustments to get it back to my happy zone.
Hope you get it sorted out. Consider this just further bullet proofing your Z. The OEM clutches all fail, it's just a matter of when.
Cheers!
-Icer
Last edited by icer5160; Aug 15, 2023 at 07:00 PM.
This replacement package combines our Z1 Nodular Iron Flywheel with the Z1 Mild Performance Clutch Kit. The result is a clutch built to OE spec clamping forces that has characteristics similar to that of the original clutch. The pressure plate along with the full face sprung hub disc allows the clutch to handle increased power of moderately modified cars without a major change in pedal feel. We find this clutch kit to be one of the best options for daily driven cars where the user wants to minimize noise / chatter without using an expensive failure prone OE dual mass flywheel.
Looks like a good kit. The clutch disk appears to be identical (made by Exedy) to the Zspeed kit. The main difference I see is the flywheel. You should be happy with the kit once installed. Hope this resolves the vibration issue.
Cheers!
-Icer
I think Z1 is making their own flywheels in house.
Elite automotive repair has the car now and I think they'll take good care of it. They are installing the clutch tomorrow and said they would adjust the clutch pedal as well. Looking forward to getting it back.
The graphs make it look quite impressive. I'm a bit disappointed though. I thought I would have gained a bit more hp. The tech said it was my cats that were holding the engine back.
It did cost quite a bit of money, but I've had a lot of fun choosing the upgrades and enjoying the results of the upgrades as each one was installed. Overall I'm happy with the results. I have a much better performing car now than I did before. It makes a nicer sound, it handles corners better, revs up a bit easier, and has noticeably more power. I like that I have proof of the power gain - that was a fun experience.
That's generally the consensus when it comes to NA mods. A lot of money for unimpressive results, but that's a good looking curve and a nice torque bump. Don't focus too much on the raw numbers as long as you are enjoying it!
The underlying disappointment with my Z is not getting to enjoy the touted 300hp it is supposed to have, even with the mods I did. I really dislike it when a company promises something and then doesn't deliver. But when I put that aside and think of it as a 250hp car, I'm quite happy with it! As you said Heel, don't focus on the numbers, just drive it and enjoy the ride.
I drove a 2004 Boxster S last weekend that has a rated 266hp and it would completely embarrass my Z in a drag race. It felt like 300hp. A much better engine than the one in my Z.
However, compared to a Boxster, my Z has a more comfortable seating position and a bit more elbow room in the cabin, it has a more comfortable ride, and I'm quite sure it will have lower cost maintenance over the long term.
The Z is the perfect car to have if you decide you'd like to own an older Boxster, because then you'll have something to drive while the Boxster is getting the ignition switch replaced, or the air oil separator, or the water pump, or the heat shield on the muffler fixed, or having the IMS bearing upgraded, or changing out the coolant expansion tank, or ???
I drove a 2004 Boxster S last weekend that has a rated 266hp and it would completely embarrass my Z in a drag race. It felt like 300hp. A much better engine than the one in my Z.
They would be about the same. It might FEEL faster, but it isn't
The underlying disappointment with my Z is not getting to enjoy the touted 300hp it is supposed to have, even with the mods I did. I really dislike it when a company promises something and then doesn't deliver. But when I put that aside and think of it as a 250hp car, I'm quite happy with it! As you said Heel, don't focus on the numbers, just drive it and enjoy the ride.
I drove a 2004 Boxster S last weekend that has a rated 266hp and it would completely embarrass my Z in a drag race. It felt like 300hp. A much better engine than the one in my Z.
The Z does make 300HP. It's rated at the crank, not the tires. ALL cars are rated at the crank. Your results are why everyone says, if you're looking for better sound, upgrade NA. If you're looking for more power, forced induction. The Z has a very good intake and exhaust from the factory. Upgrading them will sound different, but won't net much power. The Boxster will always be quicker because it weighs less and has it's weight over the drive wheels. Less tire spin.
Nice powerband overall, HP will suffer from the DE manifold, but you stated you don't rev, so numbers aside, you did the right thing.
I did suggest HFCs a few times lol.
That's a good chart. Don't get hung up on the raw numbers, pay attention to the % gain. Every dyno is going to be calibrated a little different and each will put out different numbers. To gain 30+ft/lb of torque is power you can feel and I would prefer more mid-range tq over peak hp. I take it that since you had the Z tuned, your clutch install went well and the pedal is properly tuned? Any feedback on that front?
Cheers!
-Icer
Nice powerband overall, HP will suffer from the DE manifold, but you stated you don't rev, so numbers aside, you did the right thing.
I did suggest HFCs a few times lol.
I considered that, but didn't want to add more exhaust noise. The Invidia Gemini turned out to be just the right amount of added zoom.
That's a good chart. Don't get hung up on the raw numbers, pay attention to the % gain. Every dyno is going to be calibrated a little different and each will put out different numbers. To gain 30+ft/lb of torque is power you can feel and I would prefer more mid-range tq over peak hp. I take it that since you had the Z tuned, your clutch install went well and the pedal is properly tuned? Any feedback on that front?
Cheers!
-Icer
The tune was done just before my breakdown occurred in Marietta. I think the clutch is being installed today. If not Monday. I haven't had any time to enjoy the car since the dyno/tune was done.
