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Vibration after clutch install at 100+ mph

drano38

Wayne
1,130
318
Had the Exedy Hyper Single installed a few weeks ago.
Today was my first track day, and I'm getting a vibration or low moaning sound above 100 mph. Did 2 short sessions, and stopped for the day.
Replaced items: Clutch, throwout and pilot bearing, Cobra Jet pulse ring, MGW racespec shifter, Ford Racing clutch line.
Still have stock 2-piece drive shaft. They may have disconnected it from the diff because I see bright orange paint on the rear driveshaft flange. Would re-installing it a 1/4-turn from original spot on the differential cause vibration?
Anything in the clutch that could cause it?
Hate to lose Sat and Sun track time because of an unknown noise/vibration.
 
Bummer. I certainly would try the 1/4 turn as others members have had luck with that. Is the clutch working properly? Not that I think this is an issue but did they use new flywheel bolts?
 

drano38

Wayne
1,130
318
I provided ARP flywheel bolts, so yes they are new.
My front rotors had some pretty good cracking in them, so I swapped them out just in case that could be the cause.
Stripped the drivers side caliper mounting hole, so a road trip to Auto Nation White Bear Lake Ford near St Paul to get a new one. That dealership isn't as big as I thought it would be for their good online parts business.
My instructor for today's BMW school had a GT350 for a while, so hopefully he can help diagnose the vibration if its still there.
 

drano38

Wayne
1,130
318
So far so good. Wet track for all sessions today. Drizzle to light rain most of the day. Shallow standing water on some portions of the track. Made it interesting, but provided for an educational day. Should be dry Sunday.
Didn't feel any vibration, but with the wet track, getting up to speed wasn't doable.
A GT350R showed up this morning. White with blue over the top stripes. Nice. He had a '13 Boss. I need to see if he's a member here.
 

ArizonaBOSS

Because racecar.
Moderator
8,551
2,388
Arizona, USA
Driveshaft “clocking” can absolutely cause those vibrations; hopefully that is your culprit as it is an easy fix. Whenever the DS needs to be removed, always witness mark it vs the trans and diff to make sure it goes back in th same way. Typically you won’t notice that until 100mph or more. Driveshaft angle can play a factor as well if you are lowered.
 

drano38

Wayne
1,130
318
I have Steeda Sport springs, so lowered a bit.
Stock 2-piece driveshaft still on the Boss.
A definite drive-train vibration starting at 110 mph, and gets more pronounced at 120+.
Its a high frequency, low tone. And its only there when the drive train is under load (accelerating, or engine braking). If I "throttle match" while coasting, it goes away. If I add throttle, it instantly returns.
Need to jack it up again and see if the shop witness marked the tranny/shaft connection. And validate the orange paint at the diff matches the driveshaft.
 

ArizonaBOSS

Because racecar.
Moderator
8,551
2,388
Arizona, USA
It could be possible that your carrier bearing in the stock DS is on the way out, as well. These typically don't last long at high speeds--usually the center boot blows up and sends grease all over the trans tunnel and exhaust. I think I went through two stock DSs before switching to a Dynotech unit.
 

drano38

Wayne
1,130
318
20,000 miles on the Boss, ~ 3 track weekends a year since 2011, I agree the carrier bearing is past its life expectancy (and a driveshaft has been my next planned mod). But odd that it would fail the same day they installed a clutch. I don't remember if they completely removed the drive shaft, but I'm 99% certain they took it off the rear diff.
Maybe its time to by the Ford Performance drive shaft and completely destroy the mods budget.
 

drano38

Wayne
1,130
318
Put the Boss on jack stands, and took a look.
Blaze orange paint witness on tranny/driveshaft and driveshaft/diff, so its clear they put it back on in the same alignment as it was.
Mid boot is in fine condition.
The hanger bracket bolts are tight, and the bracket does not move.
The rubber bushing in the hanger bracket is sorta soft and allows the driveshaft to be moved relatively easily. Is that normal?
 

drano38

Wayne
1,130
318
Finally, my 1,000th post here at TMO :)

Checked bushings on both ends of the UCA, and they appear to be in good shape. They're the stockers, so I can move the arm a bit but the rubber looks to be ok.
I'm pretty sure the issue is behind the tranny because the vibration is speed-related. Hitting 7500 rpm in lower gears/speeds does not cause the vibration.
As I said above, vibration starts at 100 mph, then continues getting worse thru 120 mph (that was top speed at the recent track event). Shifting into 5th reduces it somewhat, but its still there. So it seems like more load on the drive train makes it more noticeable.
An aluminum driveshaft has been on my upgrade list, so I think I'll get the Ford Performance one and hope that fixes it.
If not, then a UCA and diff bushing.
Thanks for the help guys.
 
Hey there, I just installed MGW Race Spec / Billet Flywheel and RST twin disc. Also did ARP bolts / pilot / throwout / Stainless line. Suddenly have vibration / drone (it comes and goes every second to half second at 80+. It gets louder as I go towards 100. If I push the clutch in and let rpm drop or throw the car into neutral, the vibrations still remain until my speed reduces to 80... even at idle rpm... Curious if the driveshaft was your issue and if that fixed the vibration??
 

drano38

Wayne
1,130
318
Hi Spencer, welcome to TMO!
I did install a Driveshaft Shop aluminum driveshaft, and it did not fix the vibration. They use a large CV joint at the back, so pinion angle is not a concern. I did use my adjustable LCAs to set the gap from the CV joint to the shaft per the instructions. I was 1/16 too long. I called them, and they recommended adjusting the LCAs so the gap is in the middle of their range.
On Cyber Monday, I purchased a Metco UCA and BMR poly diff bushing. I'll install those this winter, and hopefully that will be the solution. If not, I'm guessing I have a loose bolt somewhere that could take a long time to find.
 
I appreciate the reply! I'm going to swap tires to my track set to rule that out of the equation then start solving from there... Let me know how it goes with the UC and diff bushing.
 

drano38

Wayne
1,130
318
Digging up my old thread for an update.
Bad vibration is gone.
My only track event this year was the Mustang Roundup in Hastings NE a couple weeks ago.
Went out Thurs for a couple short sessions. Vibration was there like it was since my clutch swap.
Friday sessions - vibration was gone! Didn't do anything to the car, so no idea what did it. No idea if clutches need a "break-in" period or not.
The Metco UCA installed this spring didn't fix it because the vibration was there after I installed that and on the first Roundup sessions on Thursday.
Above 100 mph I get what I would consider typical NVH of a race clutch, delrin Roto-joints in UMI UCAs, and replacement Meto UCA with BMR poly bushing in the diff - NVH is there, but not annoying.
Don't know what cleared it up, but glad its gone.
 

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