I have a 93 mazda RX7 with an LS1 pull out from a 2002 F Body. I have an LS2 Fidanza aluminum flywheel with an LS7 clutch and pressure plate. I am running a wilwood 7/8 master cylinder with the stock LS6 slave cylinder. The clutch has been in the car for about 2 years. During that time I have put about 10-12k on it. The car gets driven a couple times a week and has only seen the track once.

The problem I am having is that the clutch makes a very weird noise every once in a while when letting the pedal back up from the floor. This started a few months ago and got worse. It does not do it every time. I can drive it easy and out of the blue, when I go to let the clutch out after a shift, it makes a bad swirling/chattering sound as the clutch re-engages. It doesn't matter what gear. If I get on it, it will do it more often, but not every time. I have pulled the tranny and inspected the clutch and stuff. Everything looks fine. The slave is not leaking and the bearing is good. It has a new pilot bearing which still looks good. The flywheel is perfect. no hot sports or odd looking stuff. no wear. The disc still looks new. I had the pressure plate looked at and the only thing the guy did was reset the self adjusting cover for me to reinstall. Since I could find nothing broken, I had no choice but to reassemble.

Now after putting everything back, the problem was gone for about a week. I even took my car to a road course event and ran it pretty hard and it seemed to be fine afterward. Then it started again. i think the thing that set it off was a hard 1st gear pull to 7k. During the pull , I felt an odd vibration at the top of the pull. A little while later the problem returned. Now its to the point that it has to come back out. I don't know whether to get a new LS7 pressure plate or one from an other company.

Has anyone had this problem and for sure traced it back to the pressure plate. I am thinking it has to do with the self adjusting cover getting screwed up some how. The reason I went with the LS7 setup to begin with is the daily drive ability aspect. My car is putting down around 430 rwhp. It has heads/cam/longtubes. I figured this is about where an LS7 is powerwise so this clutch would be just fine. It did not do this from the start. I have always gotten on it hard and it has been flawless. So its not the setup. something has changed but I can not find anything broke. I wish it was black and white. Also, the car still shifts. The problem is after the shift when letting the pedal back up. The pedal does feel lighter though now that it is getting worse.

 

maybe a bad motor or trans mount? something out of balance (u joint, PP, flywheel, etc)?

 

Motor and trans mounts are poly and new. Everything looks good. Don't know how to check the flywheel or pp for balance. How would this cause the noise to happen just once in a while or the pedal to now feel light?

 

Interesting...it is possible that the SAC-mechanism is adjusting unusualy but generally speaking if this happened the problem would be more consistent. Recently I provided some tech support for a customer with an unusual noise that was most noticible at start-up and at slow-speed driving but that occured with no rhyme or reason (hot/cold/in-gear/out-of-gear/moving/stopped). We talked and we talked; we thought and we thought; and eventually he pulled the trans down. In an effort to find the issue as quickly as possible he replaced the Pilot-bearing and though it appeared to be in pretty good shape it was actually the cause of the problem. I am not saying that this is definitely your issue but it is a potential cause.

 

Here is what I am up against.

1) I don't want to pull the tranny only to find nothing positively broken again.

2) I don't want to put new parts aimlessly hoping to fix it and spend money needlessly by replacing good parts.

3) I don't want to put an aftermarket clutch only to not like the drive ability vs the LS7 unit. When everything was working as it was for quite some time, it was very pleasant to drive, I had no slippage issues.

I have a bronze pilot bearing in there now, not the roller bearing type? I was told those fail. It doesn't look galled or anything. could it be spinning on the out side?

Is there a way to lock out the SAC so it cant adjust? Do these units have a high failure rate? Do the spec clutch kits such as the 3+ work with the Fidanza LS2 flywheel?

 

I talked to a guy here at Tampa clutch. He said he had a guy with a bad pilot bearing that made a weird whirling noise on and off. It looked good but was spinning on the crank side. Kind of supports what spec-01 suggested. If it turns out that that is all that is bad, ( doesn't explain the pedal feeling different) should I put a roller bearing type back in, or stick with the old style bronze bushing?

I was reading a bit about possibly having to shim. Is this necessary when using the LS7 pressure plate since it is supposed to self adjust?

 

I am confused about shimming. The slave cylinder advances with each push of the clutch pedal. One press of the pedal is not enough to fully extend the slave if it is pushed all the way in. so the 1st time I push in the clutch pedal, the TO bearing advances about 1/3 the length of its full travel. the second push of my clutch pedal another 1/3 and the last push will hyper extend it. So if the slave advances every time you push the pedal, it should take up any slack in order to get onto the PP fingers. The spring in the back keeps it against the fingers and the fingers push it back when you release the pedal. so why would you ever need a shim. if you push the TO bearing all the way to the base of the slave, then after you pump it once or twice, it will advance till it engages the PP fingers. The only issue I see is if you don't have enough volume with one stroke of the pedal to fully disengage the clutch by not pushing the fingers in far enough. Am I missing something?

 

I understand your desire to find a definitive cause for the issue...but I also realize that finding usually requires seeking and there is no way to "seek the cause of this issue" without pulling the transmission (this is of course assuming that the issue is inside the bell). I am not suggesting that you throw parts at the car...but I think it is worth the time and effort to examine the parts and determine what's happening.

Years ago, when ratcheting plates were starting to come into use, we examined a number of the available units to determine if there was a way to lock the asjuster. Though this can be done it is a very rudimentary way of solving a "possible" cause of your issue. To make this clearer, even after assessing the potential to do this we decided against it. That being the case, if this issue is SAC related then I suggest moving away from the SAC cover design rather than trying to fix a plate that has issues.

Both bronze bushings and roller-bearings are commonly used in pilot bearing applications. Though I know of people that swear by one, or the other, they are each effective and the choice is yours.

As for the echoed suggestion, by the folks at Tampa Clutch...i guess this proves that I'm not blowing smoke...of course why whould I be (LOL)? Additionally, shimming is not needed on a stock LS7 clutch kit and since you are using a Fidanza flywheel, that uses a replaceable friction surface I assume you haven't cut the flywheel which means that everything should have the correct geometry. Let me know if you have any further questions. Thanks!

 

Spec-01. the throwing parts at it wasn't directed toward you. I hope it didn't come over that way. If so I apologize. I appreciate your input. I was just stating that because a lot of times that's how people fix things. just replace everything. Obviously the pilot bearing is cheap. The slave is a little bit more. Both have very little mile on them. Which slave cylinder is the best for my application? Should I get an LS7 unit or LS6 like I have now. I am just a little reluctant to switch to an aftermarket kit if the problem I am having has nothing to do with the PP or disc. Not that that is what you are pushing, just the contrary. You have been very helpful trying to solve the problem with my existing setup.

I just took it out again and romped on it. As I suspected it aggravated the problem. Here is what I could observe. With the car in gear going down the road, if I push the clutch all the way in and rev the gas, the car makes the shuddering swirling vibrating noise. If I put it in neutral same thing. If I let the clutch out and rev it it is very hard to discern. Parked in the driveway, it doesn't seem to do it. at least not like it does when rolling.

I am going to try more scenarios and report back.