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Drivetrain Vibration

G

garner67

Active Member
During my track day yesterday I noticed some drivetrain vibration. At first I was thinking it was just an imbalanced driveshaft, but the vibration is in sync with the rpms, which leads me to believe the vibration is from somewhere from the clutch assembly forward. However, I might have my driveshaft rebalanced just to rule that out (anyone know where I can get a driveshaft balanced in the SF Bay area?).

I'll start looking into it tomorrow, but where do I start?

Maybe I'll take a peek into the bell housing to see if any clutch pressure plate bolts are missing?

Could it be a faulty harmonic dampener?

I'm open to suggestions on where to start investigating?

Background information / Engine spec:
351w is a new build (~3000 miles), and it was balanced with the flywheel. The engine ran perfect before pulling it for paint & body work, and nothing different has been done to it since it was reinstalled after paint.

While on the track as well as the drive to and from the track, the engine runs cool, starts easily (even when hot), and there are no weird sounds/knocks from the engine. I've inspected all the plugs, and they all look good, so all the cylinders are burning correctly.

At this point, it's all I know.
 
Couldn't it also be in the tire/wheels? Does it vibrate out of gear? Did you R&R the rear end?



Why is there NO video for us to watch?????????????????????????????


You know the rules :sur
 
"johnpro" said:
First thing I'd check would be u joints.
Click to expand...

Ditto.

Also, there is a thread on VMF where 68RCodeConv chased a driveline vibration for quite a while. It wound up being the trans. Not saying that's the problem. Lots of info in that thread.
 
Is there a vibration when in neutral and revving the engine? If its a balance issue from the clutch forward, it should vibrate just revving in neutral. Can rule out engine by running it up to speed past the vibration and putting it in neutral and coasting. If the vibration is still felt, most likely in drive line.
 
Quick update...

1st Step
I ran the engine sitting in neutral this morning (neighbors probably weren't happy about that). It "seems" to rev smoothly all the way up to 5k, but with my paranoid mind it feels like there is some vibration. However, a 40+ year old Mustang rev'd to 5000 rpm is gonna have some vibration... right?

2nd Step
I removed my drive shaft and took it to South Bay Drive Line. As it turns out, the shaft is NOT in balance. Not only was it out of balance, it is not even straight. There are different run out numbers at 3 different locations on the shaft. Even if this isn't the entire problem, it definitely needs to be fixed. I went ahead and bit the bullet, and I'm having a new drive shaft built. It'll be ready tomorrow.

3rd Step
I'm going to give all the accessories bolted to the front of the engine a good visual check this afternoon. Other than looking for accessory alignment and/or wobble, are there specific tests I should do to evaluate the condition of all the front accessories?
Also, I'm going to open the valve covers for a quick visual check.
 
"hivewax" said:
Didn't you say it ran fine before paint/body? I'd rule out driveshaft right there.
Click to expand...

+1 -That would make me think driveline misalignment. Of course that bent DS needs fixing.
 
"hivewax" said:
Didn't you say it ran fine before paint/body? I'd rule out driveshaft right there.
Click to expand...

Yeah, but... If you recall an older post of mine about a leaking transmission seal problem, it was from the slip yoke not having a plug to keep the trans fluid from seeping between the slip yoke ID and the output shaft. I replaced the plug on the slip yoke to fix that problem. So the only thing that has changed since paint and body work was the drive line.

Whatever the case, I'll have a brand new balanced drive shaft tomorrow, and I hope that solves my problems. Unfortunately, it's suppose to storm tomorrow, so I probably won't test drive it until Wednesday.

stay tuned... more to come.
 
Update...
I picked up my new driveshaft today. The builder reused my slip yoke and the shaft ends that hold the u-joints, but the drive shaft tube and u-joints are new. Luckily, reusing those parts saved about $100 bucks.

I installed the new shaft this afternoon and took it for a spirited test drive. No more vibration. :vic

Next stop, Knotts!
 
"johnpro" said:
Dude, I am SOOOOOO jealous. Glad you got it fixed. You're going to have a blast next weekend!
Click to expand...

Thanks, I'm definitely looking forward to my first Knotts, but you'll be missed this year.
 
I remember my first Knott's. It is what got me hooked on VMF. Was super cool! I was like a kid in a candy shop! I took the blue 66 I had at the time. We met at Don Jose's. That is where Amber and I met the same month of Knott's.

Then was MITM #1 in Morro Bay. After these two events, I was totally hooked!

Have fun!

Mel
 
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