427 engine (part 2) - RHS block

[Rich Z]

The guy I have been talking to at RPM Transmissions feels that somehow the part of the input shaft in the torque tube that rides in the pilot bushing got damaged and that damaged surface area caused the pilot bushing to become ground out and ultimately slowly failed, causing the drivetrain noise. So I believe the intermittent nature of the noise was likely from the input shaft being able to sort of flop around in the pilot bearing when the clutch pressure plate began to clamp down on the clutch disk against the flywheel. Until the clutch disk was clamped tight against the flywheel, the rotating pilot bushing would be positioned with random contact against the input shaft, making a squealing noise, depending on whether there as actually metal to metal contact. When the clutch disk became fully clamped, then the input shaft was no longer rotating inside the pilot bushing since they were then rotating at the same speed. This explains the "bearing-like" noise I have been hearing, because the noise would change in pitch as the clutch disk came up to speed before being clamped tight.

The reason this has been getting worse and worse over time is because more and more material was being ground out of the pilot bushing. And it was just a matter of luck, I guess, as to whether I would get any drivetrain noise at any given time simply because it depended on whether or not the input shaft was actually contacting the pilot bushing or not. Obviously the more slowly I let out the clutch, the more pronounced the problem could be. When I would drive more aggressively with the clutch, meaning I was letting off of the clutch pedal much more quickly, there was less time for the random position of the input shaft inside of the pilot bearing to make any noise before the clutch disk was clamped tight.

This likely explains why the noise was much more pronounced when starting to move from a dead stop than inbetween shifts while moving. The shifts while moving were much quicker than the feathering of the clutch coming off of a dead stop.

Anyway, that is my take on what I have seen of the damage, and what I am getting advice about. The one unknown at this point is if the bushing riding part of the input shaft had become damaged, that started this all off, how did that actually happen? I had preferred a brass only bushing, but I don't know if that was actually used. That brass only bushing would be far too soft to damage the steel of the input shaft, but perhaps a steel sintered pilot bushing was used, so would be hard enough to cause damage to the input shaft?

Or, looking elsewhere for the smoking gun, since this was a used torque tube put in my car back in 2012, was the input shaft already damaged then? Seems unlikely to me that the vette tech at Champion Chevrolet (now Dale Earnhardt Jr. Chevrolet) would not have noticed damage unless it was extremely subtle. The guy was pretty competent, I believe. And since he replaced the rubber bushings in the torque tube, he would have been looking at that shaft quite a bit, I would think.

Looking from another angle, perhaps those witness marks on the upper left hand quadrant of the pilot bushing are significant. Maybe the tech had a lot of trouble getting the input shaft of the torque tube into the pilot bushing. And perhaps he tried to be more forceful than usual, which seems possibly looking at those marks. As such, did that bearing riding surface of the input shaft get damaged during this install procedure? :shrug01: Honestly, this also seems unlikely, since an alignment tool is used to line up the clutch disk with the pilot bearing/bushing, so that should have been done before the torque tube was even attempted to be installed. Surely the tech couldn't have forgotten that step?

I guess I'll probably never know. But at least at this point I'm feeling pretty confident that we are looking at the smoking gun (just not seeing whose finger was on the trigger), and this can be fixed.

Finally.

Assuming I can find a new clutch that won't have it's own noise problems, which it seems that a lot of them tend to have, more or less.

Right now the leading candidates for consideration are:

• Monster LT1-SC twin disk
• McLeod RXT twin disk

But I am still doing research. I did look into the Monster triple clutch disk, but when I asked RPM Transmission about it, the guy seemed adamant that this would not be a good idea for me. He said that the extra mass of the triple clutch disks could be hard on the synchronizers in the transmission. I believe these guys would know about such things.

I just know I need to make a decision SOON, because my car can't be up on that lift at the shop forever.

Lordy, wouldn't it be NICE to finally have all the problems ironed out in this car? :dancer01:

 

[mrr23]

have you looked into https://www.exedyusa.com/

i remember them having a clutch for 1000 hp

 

[Rich Z]

have you looked into https://www.exedyusa.com/

i remember them having a clutch for 1000 hp

Haven't read too much about them, but what little I did find was about 50/50 for people liking them and not liking them. They seem to be targeting more of the racing crowd from what I was able to read about. The clutches tend to be grabby and not like being slipped any. Which doesn't make for a fun street drive.

I'm still considering the Monster triple disk, even though RPM Transmissions doesn't seem to like it. Reviews seem to rate it very highly. So I'm thinking, heck, pulling a transmission to get it rebuilt in 10 years may be a whole lot easier and cheaper than replacing a clutch on this car again. But as Connie brought up, am I REALLY going to put that many miles on the car to make any difference? :lmao: I figure I've put less than 7,000 miles on the car since July of 2012. I think under 300 miles this past year. But will I drive it more if I don't have to worry about a strange intermittent drivetrain noise? :shrug01:

I've also looked briefly at some of the other manufacturers, but kind of leaning towards the front runners in the reviews I read. Mantic used to be what I would consider ad the number 1 choice a while back, but it seems there are a number of complaints from some people about them lately. Mostly about longevity, if I remember correctly.

Anyway, I still need to do as much research as I can before I'm pressed to the carpet to make a decision on one.

Oh yeah, I noticed that Monster will warranty their clutches for a year whereas McLeod only warranties theirs for 90 days. I kind of look at warranties as being the manufacturers' indication of how robust they consider their merchandise to be. A company that warrants their merchandise for a year, expects it to last at least one year. Someone who warrants it for 90 days only expects it to last for 91 days. In my opinion, anyway.

 

[85vette]

Good luck in your search. Maybe this will help.

https://www.ranker.com/list/best-clutch-brands/ranker-cars

 

[Rich Z]

I'm putting out feelers right now to try to determine if anyone actually has concrete evidence of triple disk clutches causing excessive wear or outright damage to the transmission. Or any other notable problems. The more I think about how transmissions synchronizers work, the less convinced I become that some additional mass on the input shaft would be a notable problem. But I sure as heck don't want to put a clutch in there that several months down the road I will come to regret.

The power I am guessing my car is putting out is right around the borderline of the dual disk clutches either being organic or ceramic material. Organics allow better slipping, which is better for street driving, whereas ceramics (and derivatives) are better for tracking and racing. Hence the ceramics grip harder and more suddenly, and can hold more power. I guess there would be an achievable learning curve with the ceramic disks, but I am not sure my relaxed driving style would be compatible with how I would need to drive the car.

Wouldn't do me much good to have a clutch that makes me hate driving the car, now would it?

 

[navy2kcoupe]

Have you (or anyone else for that matter) given any thought to whether the "junk" that was abraded off of the pilot bushing got into the clutch/pressure plate area and was responsible for the marks on the plate? I know it appears to be a long shot, but I thought I would throw it out there anyway.
Andy

 

[Rich Z]

I sure couldn't rule that out as a possibility. Since that sintered material that the pilot bushing is composed of has been oil treated, I would imagine that it getting between the contacting surface areas of the clutch would make it slip like crazy. And I would think that slipping would get worse over time as more and more material affected the clutch disk. Or maybe not. Perhaps the small quantities involved just got burned off by the heat of the friction, leaving the marks we see. :shrug01:

That being said, thinking out loud, I would imagine that material would have been slung all over the place and showing up in every nook and cranny in the clutch. Especially so in the splines of the input shaft of the torque tube and on the face of the flywheel where the bolt heads are located holding it to the crank. Which, as best I can tell, was not the case. Seems unlikely that it would ONLY get between the clutch disk and the contact surfaces of the pressure plate and flywheel.

Yeah, I know it would be logical to look for a common single cause of the two problems evident (1. crud around the pilot bushing, and 2. burn marks on the pressure plate and flywheel), but I am leaning towards thinking they are two separate issues. Actually I am surprised that the clutch disk doesn't show pronounced wear at the outside edge of the disk, since it is possible that it was contacting the pressure plate and flywheel at a slight angle if the pilot bushing wasn't holding the input shaft centered. But I don't see any obvious evidence of that. So I am thinking that the squealing noise was from the contact between the input shaft and the pilot bushing, and not the clutch itself. As many times as I have heard that noise, I would imagine that if the clutch were making the noise, there would be more evidence of it. Beyond the burn marks of course, which I would not think the low rpms at play when taking off from a dead stop normally, would cause. If I had been doing 6K rpm launches, well heck yeah, that might explain it.

I'm really leaning towards thinking that the Centerforce clutch just wasn't up to snuff for my car, and has been slipping all along. Of course, one of the test rides I took using EFIlive to monitor everything was specifically to look for a slipping clutch while under boost at high rpms, and I did not see any sign of them. The display line for car speed compared to engine rpm was pretty much linear. A slipping clutch would show up (IMHO) as engine speed suddenly increasing at a sharper angle than car speed (meaning wheel rotation against the pavement) as the flywheel and pressure plate started spinning at a higher rate than the clutch disk. But never having actually seen that in practice, I am just guessing. :shrug01:

Which I have had to do pretty much all along with this stuff.

 

[Rich Z]

My intention is to have all of the following replaced:

• Pilot bearing (bearing this time, NOT bushing)
• Flywheel
• Clutch assembly
• Throwout bearing/slave cylinder
• Torque tube input shaft
• Both torque tube bearings

The drivetrain is already out of the car, so no sense half stepping now.

I have been conversing with RPM Transmissions and the guy I have been talking with recommended that based on what he sees in the pressure plate and flywheel, that I NOT use an organic based clutch disk. I had been planning on using a McLeod RST clutch, but I will have to now consider using the RXT instead. He said he would not recommend the Centerforce clutch at all.

Well, I have parts ordered and when they all show up, the install will take place and hopefully the drive train issues will be behind me.

I ordered the Monster LT1-S triple disk clutch. https://www.tickperformance.com/mon...nd-flywheel-package-torque-capacity-1150rwtq/

Ordered the above from Tick Performance along with the spacers for the slave cylinder/throwout bearing in case they might be needed. https://www.tickperformance.com/tick-performance-slave-cylinder-shim-kit-3-pack/

Also ordered a new torque tube input shaft from RPM Transmissions and they will be pressing the front TT bearing onto this shaft for me.

The clutch assembly will be coming with the pilot bearing and slave cylinder/throwout bearing included. I believe this is a ZR1 throwout bearing, since it is shorter than what comes as stock in the Z06 and is needed to make room for the thicker 3 disk clutch system. But it is an aftermarket "Billet Howe" slave, not a stock GM unit.

The throwout bearing coming in the clutch kit might have the longer remote bleeder attached to it, but I'm not certain about that. In any event, I already have one I purchased separately from Tick Performance a while back in preparation to this job. Just seems like a good idea to be able to exchange and bleed the clutch fluid every now and again.

The front bearing in the torque tube actually appears to be fine, with no noticeable end play or runout, and the torque tube input shaft end that rides in the pilot bearing actually cleaned up nicely, and measures within GM specs, but I just feel better replacing them both. With the input shaft apparently bouncing around in the pilot bearing the last few years, I would rather not chance putting it all back together again to find out that the front bearing was damaged in such a way that it only shows up under load. Like making a squealing noise when taking off from a dead stop and letting out the clutch pedal.

I didn't see any reason to replace the two rear torque tube bearings (yes, there are two), since it was unlikely they got damaged in any way, and they are actually a pain in the butt to change out. The rubber couplings on the drive shaft should be fine, as they have less than 7,000 miles on them from when they were replaced back in 2012.

Also of note, one of the gaskets on the rocker arm covers was broken with a noticeable gap in it. So I ordered a new set of gaskets as well. Odd that I really didn't notice any oil leaks around the rocker arm covers, though.

Evidently Monster builds these triple disk clutches when ordered, so the guesstimate is for 7 to 10 days to build and test the unit before it is shipped out.

I checked into that Monster clutch extensively, and found the reviews for it were generally all very positive. There was an incidence of someone not checking the gap between the throwout bearing and the fingers of the clutch, which resulted in him having to take it apart again to put a shim in place to make the gap correct, but beyond that, nothing of note. Monster STRONGLY recommends reading the install instructions and following it closely. They stress marking everything before taking it apart for the install, and under no circumstances separating the topmost section which contains the pressure plate, top clutch disk, and the first plate that contacts the second clutch disk. Must be something special done during the manufacture of the clutch that would be a problem to deal with in the field.

Yeah, it's more money than I wanted to spend on a clutch, but it is what seems like the best option for my car, all things considered. But time will tell, I guess.

So with any luck by next month the drivetrain issue I have been having for years will be over with.

 

[Rich Z]

Got the new torque tube input shaft from RPM Transmissions with the front bearing pressed into place today (Thursday). Looks in pretty good shape, but I'm not sure it is a *true* GM product. But I checked the front bearing surface and it is the correct diameter, and the length matches an old shaft I have here in one of the cabinets. I doubt RPM would use anything that was an inferior product.

The splines on the shaft that go into the clutch disks are a little bit longer than my original input shaft, which I guess is a good thing since that triple disk Monster clutch will likely be a bit thicker than a stock clutch.

One thing of note is that I tried both a new pilot bushing and a new pilot bearing I have laying around here on the input shaft end and the bearing seems to fit the shaft a LOT snugger than the bushing does. Actually a noticeable wobble in the bushing. So likely a good thing I am using the bearing this time, as I don't like that much play between the shaft and the bushing.

Also got in the shims for the throwout bearing/clutch slave cylinder, in case they might be needed. I was told that more than likely they won't be, but it is just a real good idea to check that spacing between the throwout bearing and the clutch pressure plate fingers, just to be certain.

I also picked up a set of valve cover gaskets, hoping they are the correct ones.

Hopefully the clutch itself will come in next week or so. Would be nice to get this wrapped up soon.

 

[Rich Z]

Well, hold on a minute....

OK, maybe I am just too picky to be healthy.* Been looking at the photos I took yesterday, and REALLY looked at things closely.

I asked the RPM about this, asking if this was a genuine GM replacement part and was told that the C5 torque tube input shafts are no longer available new, so the C6 input shafts are being machined down to fit the C5.

Well that is all and good and everything, but darn if it doesn't look like the area in front of the splines was worked over with a hand file.* And honestly, I'm not all that crazy about the stub that goes into the pilot bearing being polished rather than just left with the raw machining parts.

So let me ask you this. Would you put this input shaft in YOUR car?* Am I just being way too picky about this?* Or will this be perfectly OK?


:banghead:

 

[Rich Z]

For reference, this is the torque tube input shaft currently in the car after the tech polished up the stub that goes into the pilot bearing:

He said he checked and the shaft has zero runout and zero play.

:shrug01:

 

[Rich Z]

Well, the apparent manufacturer of this input shaft I bought (AMP Distributing) says in a post in a thread I posted elsewhere about this:

The sleeve pressed on is a case hardened bearing material and designed to work with a pilot bearing.

I didn't realize that I was looking at a sleeve pressed onto the stub end of the input shaft. But the guy says this will be fine. Still, I wish it had been polished somewhat smoother than my closeup pics are showing. Holding the input shaft in hand, it does look just fine, so maybe I am just looking at it far too closely to where what I am seeing just doesn't matter. I measured the stub, and it comes to 0.590", which from what I have been told, is GM spec for the diameter of that end that goes into the pilot bearing.

But I still haven't heard why it looks like the area in front of the splines appears to have been hand filed, instead of machined. But does it matter? :shrug01: Maybe I am just expecting perfection in an imperfect world.

Something tells me that if I used that same camera to take pics of the stub on that input shaft that came out of my car, I would likely have a heart attack, even after the tech polished it up. :hehehe:

 

[Rich Z]

Well, sort of a "smoking gun", I guess. The material around the pilot bushing was checked, and it is magnetic, as is the pilot bushing itself. When I had the drivetrain work done at the local Chevy dealership here, I specifically requested that a pilot bushing be installed instead of a pilot bearing. And that the bushing be non magnetic (non-ferrous). I said this to the tech directly. Obviously that last part was ignored.

I suppose I understand now why when I contacted Dale Earnhardt Jr Chevrolet, where that particular tech is now the shop foreman, why they never got back to me about bringing my car back into their shop to diagnose a drivetrain noise.

Everything I read concerning using a pilot bushing strongly recommended against using a pilot bushing made out of sintered steel instead of pure sintered brass. I guess now I know why. :banghead:

 

[Rich Z]

Well, the new clutch from Monster is scheduled to be delivered sometime on Tuesday. So from time of order (10:00am 04-25) to actual scheduled delivery (05-14) we are talking about 19 days. Honestly, had I known the delay would have been this long, I think I would have looked harder for another brand/model that was on the shelf and ready for immediate shipping. Maybe I'll feel differently about it when it is installed and hopefully will be tickled pink about how it performs, but historically, my surprises concerning this car and the problems I have faced over the years have not been pleasant ones. So I'm not holding my breath thinking the excessive wait will prove to have been worthwhile.

So we will see how this turns out.

 

[Rich Z]

So the machine marks on the stub of that input shaft have been bugging me ever since I received it. I talked with a representative of the company who actually made it and expressed my concerns, but he said it will be perfectly fine "as is". So I asked him if I could polish it up a bit, or would that negatively impact anything by doing so. He said it likely wouldn't have any impact either way, and if it would make me feel better, and I didn't get carried away with it, to go ahead.

So I did....

Chucked it up in my little lathe and then used increasingly finer grit polishing paper (from 1500 grit to 3000 grit) and then applied some Simi-Chrome.

BEFORE:

AFTER:

I wasn't inclined to take off too much metal to try to get all the machine marks out, just enough to make any riding surfaces of the shaft on the pilot bearing smooth and silky. As frictionless as practical. Shaft nub feels smooth as butter now.

 

[Rich Z]

Well, this is *special*.

The clutch shows up via UPS around 10:30 am. Was planning on running it right out to the shop, but I have been recovering from a pretty bad migraine headache and decided to hold off for a day. So early afternoon, UPS shows up again, bringing another box from Monster Clutch. Which, btw, I knew nothing about ahead of time. Well, turns out that apparently they didn't have the slave cylinder ready when they shipped out the clutch, so they sent the slave separately afterwards but over nighted it. Swell, I thought.

Anyway, here is what I bought.

https://www.tickperformance.com/mon...nd-flywheel-package-torque-capacity-1150rwtq/

Note the image of the slave cylinder/throwout bearing in the above pic? In the advertising text in the link above, it plainly states that the shown slave cylinder is for the 1997-04 C5 Corvette. Which I certainly bought this for.

Well when I opened up the box I got, here is what I found inside.

OK, so maybe this is one of my dumb days brought on by that migraine headache, but darn if I can figure out how this slave cylinder they sent me is supposed to be installed. The stock unit needs to be bolted onto the engine side of the torque tube, with the input shaft running through it. So unless I have to JB Weld this thing to the torque tube, darn if I can figure it out. :thinkin:

Bad enough that had Connie and I just grabbed that clutch box and ran it out to the shop without opening it, there wouldn't have been ANY slave cylinder in it, unbeknownst to me. But heck, I'm not sure this is any better, except it saved us a wasted trip, of course. But I sure don't have a clutch that can be installed right now.

 

[Rich Z]

Well, here is the scoop. Evidently when the clutch was sent out to me, AND when the slave cylinder was also sent out to me, Monster neglected to include a bracket needed to mount the slave cylinder to the front of the torque tube. So they overnighted it to me, and I got it this morning. NOW things are making sense to me.

At first I was concerned about there not being a spring included in this kit, as is found in the stock slave cylinder, but I was told it is not needed in this design. When I fit the two pieces together, it's a really tight fit, so I don't think any spring is needed. Matter of fact, with this design, the throwout bearing won't be constantly pressed up against the clutch pressure plate fingers as a spring operated one would be. So perhaps less wear and tear on that bearing, hopefully.

So anyway, I had everything I think I needed, and Connie and I ran the stuff to the shop so they could work on in whenever they could. With any luck, I'll have the can back in a week or two. AND hopefully the awful drivetrain noise will be gone.

 

[Rich Z]

Speaking of drivetrain noise, I'm pretty much convinced that the pilot bushing is the smoking gun here.

I was able to bring that old pilot bushing home with me, and the pictures are showing some pretty awful gouging on the interior surface of the bushing. And that bushing is definitely magnetic, so that sintered steel bushing rubbing against the stub of the input shaft to the torque tube obviously were making some music together. Had the bushing been pure brass as I had requested, then I likely wouldn't have even heard anything.

Still not sure what exactly CAUSED the gouging, though, but it looks like the tech who installed this stuff back in 2012 wasn't all that gentle about it. But was that the real root of the problems I had after that repair? :shrug01:

 

[Rich Z]

Something else that the tech found of interest. I've had a small oil leak at the rear of the engine on the driver's side for quite a while now. Not bad enough to actually look into where it was coming from. Well apparently the valve cover gasket on that side had a section of it just missing. Not just a crack or a split, just a section of about a half inch just gone.

I'm not sure when that happened. Those valve covers were originally put on by Aaron Scott. I'm not sure the tech at Dale Earnhardt Jr. Chevrolet remover the valve covers or not when he worked on the drivetrain. Seems unlikely that the section of gasket just fell off recently, but who knows?

Since this is an aftermarket valve cover set, and I don't know who made it, I'm having trouble finding replacement gaskets for them. So perhaps whoever caused that or even noticed it later on, had the same problem and decided to just ignore the problem and put it back together again anyway. I would have thought that someone could have at least permatexed the gap. :shrug01:

 

[navy2kcoupe]

Wonder if it shrunk because of the heat? Is the other one off too? What's that one look like? Lotsa possibilities for blame given the number of people that have their grubby little mitts inside the engine compartment. Unless someone owns up to doing it, you"ll never know. Good find by this tech nonetheless! I would hope that the gaskets used on the rocker arm covers would mostly be standardized, but apparently not. Good luck finding replacements. Hope you don't have to buy new covers to get the problem solved........
Andy