Despite careful work and all efforts to do it right, the new Centerforce clutch has a rather nasty shudder when launching the car in first gear. Once engaged and during all subsequent shifts, there is no issue. Only when I take off in first. The slower the engagement, the worse the shudder. Bad enough to worry me and pretty violent at times. We are going to tear it down this weekend to see what's up, but wondering if anyone has any ideas as to what the most likely issues may be. Clutch was installed by a very qualified person, so contamination and the like are not concerns. Wondering if the pressure plate was dropped or bent in shipping?? Very small possibility that clutch plate is on backwards - but not likely. Would that give such a result? I hate to take up anyone's valuable time tearing this down a second time, so focusing on most likely causes will be a great help. I appreciate the input folks have or if you've experienced similar issues. Thanks
Causes of Clutch Chatter or Shudder Improper break-in procedure Flywheel not properly resurfaced before installing a new clutch Flywheel or clutch disc friction surface not parallel with the crank flange surface Flywheel has severe hard spots or hot spots Flywheel has an improper step or cup dimension Defective pressure plate and/or disc Disc has inadequate or no marcel (not enough cushion between friction facings) Oil or grease contamination on clutch facings Worn or damaged clutch linkage Bent cover assembly and/or clutch disc Damaged/excessively worn U-joints or CV joints Misaligned U-joints Excessive backlash in differential Excessive driveline angle Improper gear ratio versus tire diameter Improperly tuned engine Worn/damaged engine or transmission mounts Bad leaf springs, bushings or mounts
Flywheel was resurfaced at a reputable machine shop. Looked good . Beginning to think I may have simply drawn a short straw with a bad pressure plate. We'll see this weekend. Thanks
Which type of Centerforce clutch do you have? Some folks have had issues with the Centerforce "DFX" clutch chattering. http://www.v8buick.com/showthread.php?151413-Centerforce-dual-clutch-vs-DFX-clutch
Wrong type of clutch disc material will cause chattering, especially the more race oriented ones that have higher metal content. They can be very ON/OFF on their bite onto the flywheel. I wouldn't be quick to blame the pressure plate. Very unlikely the clutch disc is in backwards. I did just that last summer. The result was there wasn't enough adjustment in the clutch linkage to make up for the slack created by the disc hitting the crank hub and pushing the pressure plate outwards. Effectively making it like the clutch pedal was pushed all the way down even though it wasn't (plus the clutch disc friction material wasn't touching the flywheel).
What gear/tire size are you working with? Mine used to have a 3.08 with the M-22 and would always chatter, it went away when I installed the 3.90 did you check the bellhousing alignment? that will make it chatter as well. Does the pedal operate smoothly?
Thanks guys for the tips/questions. Flywheel was resurfaced, pilot bushing replaced. Clutch is a dual force, not a DFX. Operation is smooth and it is quiet in neutral. On the matter of alignment, wouldn't I notice vibration in all gears/shifts? Engagement is pretty close to the floor, but several adjustments were made, so I think it is operating correctly. Guess we'll need to see what we find when we open it up. Prior clutch was smooth on engagement and operated fine, just a very heavy pedal feel. I'm sure we'll figure it out and I'll let folks know.
Funny you should ask! Just spoke to Brian and he has the car back together. He's rather pleased with it, so I'll go get it tomorrow. Let's review the bidding.... Pulled things apart last weekend. Badly burned flywheel with som eheat cracks. Corresponding burns on pressure plate. Noted some strange green grease on the input shaft and figured out it was excess from the new throwout bearing. May have been too liberally greased? Working guess is that the bearing grease flung to the flywheel and PP and burned?? Took flywheel to be resurfaced and they checked runout. Perfect. Everything went back together clean as a wistle. So far, seems fine. Could have been a bad PP, clutch disc, who knows. Hated to see Brian go thru that twice. Now just need to log some miles! I'll update with miles gone by. Steve
Been driving the car all summer. Second clutch assembly proved better, but still has shudder. I lug the motor down to next to no RPMs and she'll launch ok. Still notice shudder frequently and when I down shift. Brian and I will get this back apart before winter and sort out what's up. May be an alignment issue. I'm intrigued by the comment about bellhousing alignment. I would not have guessed it was an issue based on how the BH bolts on. How is alignment adjusted? Could be that for sure with the first attempt being more off than the second. Need some education. Thanks, Steve
They make offset bell-housing alignment dowels. I think it's Mcleod, Lakewood and maybe some others (RobbMc and others) http://www.robbmcperformance.com/products/dowels.html
How was your ballstud distance to the flywheel? I run that centerforce setup and have silky smooth engagement. I measured my thinning flywheel (300k+ miles) and lengthened the adjustable ballstud accordingly. That entire pedal-linkage-geometry thing should be investigated.
Since no one has asked, did you just convert the car to a 4 speed from an automatic or did you simply replace the clutch and ? If just a new clutch was installed, how did the old one work?
Brad, Is there a spec on the distance between the ballstud and the flywheel? I've always installed the ballstud measuring off the back of the block. I believe it's 3.75". I have it written down somewhere...
Unless the back of the block or front of the stock BH have been surfaced that dimension will never change. But the fork to flywheel face dimension will change as soon as the FW is surfaced; and this will alter the fork throw geometry. The FW has a stock dimension listed in the service manual. As the flywheel gets thinner the ballstud must get longer to maintain stock fork-to-flywheel geometry. Probably does not matter for the first few resurfacings. Eventually though the growth in this tolerance will have an effect that is more noticable at the pedal because of the mechanical multiplication inherant in the pedal throw to fork throw ratio.
I recently installed a scattershield and thought I measured mine out to a proper 3.75", but the pedal engagement was near the floor and over a very short range of pedal travel. So I ran the pivot point out some until the pedal feel was good and even over the whole range of pedal travel an that seemed to help a ton. Pedal effort went down and the clutch was less grabby with more control over the pedal travel range. Don't know if that is your problem or not, but I know I fubar'd the measurement or something when I put mine together and I had to do some serious adjusting afterwards.
Sorry Guys,. Just getting back to this. This is a factory 4 speed car and the previous clutch engaged very smoothly. I nly changed it out to lighten up the pedal as the one it had was extremely heavy and not much fun in any traffic at all. Starting to wonder more about bellhousing alignment and may need to check that. I see that Browell makes a slick alignment tool for this purpose. Does anyone know if this is available for rent at any of the prts places ( Autozone, etc..)? Thanks, Steve
Since it didn't have the problem before the new clutch and pressure plate were installed, I'd be looking at what was changed rather than what wasn't rather than trying to reinvent the wheel. How was the flywheel resurfaced? Was it turned or was it milled? I guess I'd want to have it checked to make sure it's square with the mounting surface, possibly by another reputable shop. If that checks out then I'd be calling Centerforce and telling them how unhappy I was with their product. I've put at least a dozen of those dual friction clutches in customers musclecars and have never had a bad one but I have heard a couple stories of people having problems with them.
