Clutch fork vibrating against footbox

HSSS427 · #1 (**permalink**) 12-03-2006, 06:47 PM

Have an ERA with a 427 so, Tremec TKO 600, and Lakewood scattershield. I'm getting a bad vibration when I depress the clutch and it feels like the clutch arm is vibrating against the bottom side of the footbox. I can feel the vibration through the pedal and it makes a bad vibrating noise. Haven't had this before and just re-installed the engine and tranny.

Is this just a clearance issue with the fork hitting the footbox, or is it a sign of something worse ie bad throwout bearing or the like? Thinking of changing to the Forte system where the slave is attached to the bellhouse, but don't want to take the tranny out now that I've just gotten it back in. Any suggestions or things to check?
Thanks!
Scott

rblong · #2 (**permalink**) 12-03-2006, 08:56 PM

I am not famalier with ERA. Mine is hydraulic mounted to bellhousing. I yours direct pedal pushing the clutch fork? If so, and your getting a bad vibration when you depress the clutch I would be thinking throwout, Does you bellhousing have an inspection cover on the bottom? If so you can look and see from there.

Bruce

strictlypersonl · #3 (**permalink**) 12-04-2006, 05:09 AM

Has the corner of the fork been trimmed as per the manual?

If the fork has already been trimmed, you might have to lower the back end of the trans by using a different mount.

undy · #4 (**permalink**) 12-04-2006, 05:23 AM

just curious... Was the Lakewood "dialed in" for crank/input shaft concentricity? If not, one of the resultant symptoms is very similar to what you're describing.. If there's an alignment issue then there's undue lateral loading of the input shaft/pilot bearing or bushing. Eventually this will cause the pilot bearing/bushing to wear and ultimately fail. The end result is input shaft whip, due to misallignment and now no pilot bearing to keep it in toe. If the shaft is whipping then the throwout bearing is too. That will all transmit to a "feel" in the pedal. In extreme and neglected instances it can also lead to tranny failure and premature main bearing wear.

..not saying that's your problem but it sure is suspect.

Dave

HSSS427 · #5 (**permalink**) 12-04-2006, 06:27 AM

Thanks guys. The setup is a hydraulic with a master cylinder on the frame and a slave cylinder attached to the block that acuates the arm.

I did have the Lakewood aligned by Keith Craft when he rebuilt the motor. I think Bob may be on to something as I did put in a new tranny mount setup when I last re-installed the engine so it may be sitting a tad bit higher. Will also check on the cut-off of the fork. Still using the original fork that Phil Cool installed when he built it and had assumed he would have done that.

Also, it's a new throwout bearing that was installed about 200-300 miles ago. Any way to tell if it's good or bad without pulling the tranny? Also, RBLONG, no inspection covers on the Lakewood.

HSSS427 · #6 (**permalink**) 12-12-2006, 05:58 PM

Today I ran the car and the throwout fork is vibrating up and down against the bottom of the footbox when the car is in neutral and clutch pedal is out. When I push the pedal in I get an initial harsh vibration as it engages, and then it goes quiet. Thus, each time I shift gears it feels like a chainsaw is being put against the bottom of the foot box and it's transmitting the vibration through the clutch pedal. When the car is running in gear I'm still getting a slight vibration. I haven't had this problem in the past and am trying to figure out what would cause this. The throwout bearing was installed new about 250 miles ago.

First, I assume it's not normal for the fork to move up and down so it's not just a clearance issue. Given that, what could be causing this?

- the fork / bearing is not releasing all the way out? ie when the car is in gear, the throwout is still contacting the presure plate splines?
- could I have bent or broken a pressure plate spline and it's hitting the throwout bearing?
- The bearing is bad and not spinning freely?

Any ideas or experience with this? Don't want to go through yanking the tranny out if I don't have to since it's such a pain.
Thanks!
Scott

Burgs · #7 (**permalink**) 12-12-2006, 07:47 PM

Is the pivot ball for the fork on the passenger side? If yes, could the end of the fork have come off the pivot ball? Actually, I guess the same could happen with the pivot on the driver side also.

HSSS427 · #8 (**permalink**) 12-12-2006, 07:52 PM

No, it's a Lakewood scattershield on a 427 FE with Tremec TKO 600. It uses a clutch arm that has a clip on it that slips through a slot on a bracket inside the bellhousing that acts as the pivot. The bellhouse opening is on the driver side. Clutch arm is actuated by a Tilton slave cylinder bolted to the block.

BTW Burgs, with that Avatar feel free to post to my questions anytime. I mentioned in another post that your avatar and lovehamr's always seem to make me take a bit longer to read your posts.

Burgs · #9 (**permalink**) 12-12-2006, 08:04 PM

Just make sure the fork is not some how hitting the pressure plate housing as it's spinning,... as if the fork is too far forward. It happened to me while I was sorting out some incompatible fork parts.

Partial credit for the avatar goes to Lineslinger and the Cardinals.

HSSS427 · #10 (**permalink**) 12-13-2006, 02:44 PM

Called Centerforce and he said there's not enough clearance Clarence for the throwout bearing to move up and down that much, so the fork must have come loose from the bearing clips. I said makes sense and thanks.

So started messing with the fork while trying to peak up inside the bellhouse and guess what the bearing was moving up and down. Hmmmm....

So pull the tranny out, and guess what - wrong bearing size - the hole in this one is 1 3/4" and the Tremec input shaft is a good bit smaller than that. So the thing was wobbling all over the place.

Now, I'll go replace it, but I'm not sure how I ended up with the wrong one.....