Trying to diagnose clutch chatter - 1st gear only ??????

NorCal Cobra · #1 (**permalink**) 07-02-2008, 03:37 PM

Please Help!!!!!

My Cobra has gradually developed clutch chatter.

Engine- 427 Stroker motor (2,000 total miles on motor, car, trans, etc...)
Tranny - TKO 600
Clutch - McLeod w/ Willwood slave cylinder setup

The front end of my Cobra chatters and shakes only when I am starting to roll from a dead stop and only in first gear. Once the clutch is disengaged and the vehicle is above 5 MPH, I have no issues and the car work perfectly. It will not chatter in reverse from a dead stop either.

I have been easy on the clutch with little slip and very few hard launches.

The chatter is much worse when going up a steep incline. I have read numerous threads that it may be the Pilot Bushing, warped flywheel, glazed clutch disc, loose motor or tranny mount, and various other possible problems.

The tranny and motor mounts are all tight. I don't belive it is the flywheel or clutch disc, because it only occurs in first gear and I am not receiving any vibration feedback through the clutch pedal.

I am trying to get some input before I decide to pull the entire tranny and clutch.

If you have any possible solutions, please let me know.

Thanks,

Mike

wtm442 · #2 (**permalink**) 07-02-2008, 04:28 PM

What happens when you take off from a dead stop in second gear?

Have you tried bleeding the hydraulic clutch setup? Might be air in the system.

NorCal Cobra · #3 (**permalink**) 07-02-2008, 05:11 PM

I haven't tried taking off in second gear, but I will within the next few days.

I installed a new Willwood cylinder last week, but the chatter was still there prior. Perhaps I did not bleed the line completely. I have it on stands right now, so I'll try to bleed the system a little more today or tomorrow.

Thanks for the suggestions.

DAVID GAGNARD · #4 (**permalink**) 07-02-2008, 05:31 PM

Been there,done that, forgot to put the pilot bearing/bushing in the rear of the crank, it'll do it everytime!!!!!!!!!!!!
Either way, you're gonna have to pull things apart to fix it........my vote is the bushing.............it's very easy to forget to put in and overlook........

My car did the exact same things you describe, brought it to a local mechanic and after he let off the clutch one time and felt it, he called right on the spot and he was right....I guess 25 years expirence will do that for you......

David

jwd · #5 (**permalink**) 07-02-2008, 06:53 PM

Sounds like a contaminated disc. The lack of a pilot bearing would not cause a chatter to come on gradually after 2000 miles, it would be right away.

Jim

vector1 · #6 (**permalink**) 07-02-2008, 07:02 PM

Quote:

Originally Posted by jwd

Sounds like a contaminated disc. The lack of a pilot bearing would not cause a chatter to come on gradually after 2000 miles, it would be right away.

Jim

unless the pilot bearing gradually went bad. either that or i agree, contaminated disc surfaces. either way, brace for a teardown.

Roush #1 · #7 (**permalink**) 07-02-2008, 07:53 PM

Mike,
I have heard of several others who have experienced the same problem...
clutch chatter in first gear only after a couple of thousand miles.

Several have narrowed the problem down to clutch adjustment and improper slave cylinder mounts, ie. the slave cylinder mounted to the frame and the engine and transmission moving a bit from initial torque causing the clutch to slip or chatter a bit when the engine moves on initial take off in first or any other gear. Slave cylinders work best when mounted to the engine or transmission.

The first thing I would check would be clutch adjustment and slave cylinder mounting location.

Just my $.02 worth.

Hope this helps.

Jody

PS....just curious why you replaced the slave cylinder - the same folks who have the cylinder mounted on the frame experience frequent slave cylinder failures due to tension placed on the rod on the moving end of the cylinder when the engine torques over.

CHANMADD · #8 (**permalink**) 07-02-2008, 09:07 PM

More often than not it is not the clutch but some play somewhere in the driveline. A worn universal can do that ,so can a rear hub bearing,it could also be that the driveshaft is not properly aligned. I would check for play inthe driveline first before taking things apart..

imo

Got the Bug · #9 (**permalink**) 07-02-2008, 09:57 PM

Mike - What kind of oil leaks (if any) are you experiencing? I had a situation where an oil leak contaminated the clutch surface and I started to experience clutch chatter at about 2K miles in first gear when the car was hot. Ended up having to replace the clutch.

Rick Parker · #10 (**permalink**) 07-02-2008, 10:02 PM

Another thought, if the disc is a "Race" type without the Marcel springs or a sprung hub it may have become glazed from gradual engagement in a "Street" environment. I would place my bet on the disc regardless of which type you have.

Speedysnake · #11 (**permalink**) 07-03-2008, 05:23 AM

Mike,

I had the same problem with a wilwood external slave cyl. With the fixed end of the slave mounted to the frame, there can be chatter on start up. I remounted the fixed end of my slave to a bracket attached to the engine and solved my problem. I hope this helps. There is a pic in my gallery.

Paul

JBCOBRA · #12 (**permalink**) 07-03-2008, 07:00 AM

Sometimes you just have to beat them harder. Go out and beat the hell out of it and your problem should go away

NorCal Cobra · #13 (**permalink**) 07-03-2008, 07:57 AM

Thanks for all your suggestions. My slave cylinder heim joint is attached and secured by an "L" bracket attached to the frame. I think I'll try to adjust it before an entire tear down.

Can the problem really be a contaminated disc? I would think the clutch would slip before any chatter would occur. Also, wouldn't chatter occur in every gear if the disc was contaminated or the flywheel was warped?

If I feather the engine and clutch just right, I can virtually eliminate any chatter (except on an incline).

The driveline appears to be fine and I am not having any rear main leaks. I think I can rule out anything from the drive shaft back.

The fact of the matter is that something is seriously wrong and baring a simple slave adjustment, a complete breakdown is iminent. Unfortunately, I lack the free time needed to drop the transmission and make any repairs. I will try to find a knolwedgable and honest mechanic here in Northern CA.

I think the easiest way to simplify what is happening is to say that the problem occurs when the clutch disc is releasing from contact with the flywheel. I believe it it one of three things would cause this:

1. Slave cylinder
2. Clutch disc or flywheel
3. Missing or out of round Pilot Bushing

Thanks everyone,

Mike

Bxx1 · #14 (**permalink**) 07-03-2008, 10:12 AM

Unfortunately, I lack the free time needed to drop the transmission and make any repairs. I will try to find a knolwedgable and honest mechanic here in Northern CA.

Mike,
I can recommend Gary Cook at GT Auto in Rancho Cordova, excellent/honest mechanic with lots of experience on Cobras etc. Please keep us informed/updated of the repairs. Good luck.
Ron

lovehamr · #15 (**permalink**) 07-03-2008, 10:28 AM

Quote:

Originally Posted by NorCal Cobra

My slave cylinder heim joint is attached and secured by an "L" bracket attached to the frame.

I'd bet that this is it. That would be the first thing I did before tear-down.

Steve

MrMagoo · #16 (**permalink**) 07-03-2008, 11:40 AM

I'll go in with everyone who thinks it's the clutch slave being mounted to the frame. I had that problem real bad, exactly as you describe. It went away when I mounted the slave to the engine mount, instead of the frame.

If it were the pilot bushing, would it also chatter when engaging second?

NorCal Cobra · #17 (**permalink**) 07-03-2008, 12:58 PM

Why would it make a difference if the heim joint is attached to the frame vs. the engine mount? Both are fixed rigid points on the car that allow very slight movement, if any.

I'm just trying to understand the dynamics of the setup. Unfortunately I have a Lakewood Belhousing and the clutch fork extends much lower (further away from the engine) than with Quicktime and others out there.

Since the slave cylinder sits so much lower, it is very difficult to fabricate a bracket that would attach to the engine mount.

Speedysnake · #18 (**permalink**) 07-03-2008, 01:15 PM

Al,

Unless you have absolute rigid motor mounts, the engine will move due to the torque on start up. This changes the distance from the fixed end of the slave cyl. to the clutch fork. I had exactly this situation on my BDR with the frame mounted slave cyl. I installed a bracket, hanging from the rear bolt on the left side motor mount, and attached the slave to that. This way the whole assy. moves with the engine torque. Problem has been gone now for over 3K miles

Check out the pic on my gallery.

Paul

NorCal Cobra · #19 (**permalink**) 07-03-2008, 01:24 PM

Thanks Paul. I'll see later today if it would work with my current setup.

Mike

tcrist · #20 (**permalink**) 07-03-2008, 01:25 PM

Norcal,
I think that maybe the slave mounts to a bracket that mounts to the engine. That way everything moves at the same time. You just need to have a flex line to your slave. When I was looking for a kit for my T5, there was one that bolted right up to "2" tabs on the transmission. It was a "push" from the rear to replace using the cable "pull" clutch. I ended up staying with the cable.

Terry