Physics and drivetrain vibration

[COramprat]

I have a vibration in the drivetrain that has me puzzled. At 65 or so there is an ever so slight vibration...almost not noticeable unless I stay at a constant 65. It goes away past 70-75. Now as that speed doubles the vibration is even more pronounced...the shifter vibrates pretty violently and it can be felt throughout the car but once the speed drops it goes away.

I've had u-joint issues in the past and this doesn't seem the same. The vibration appeared around the same time as my clutch swap last year but after my mechanic fixed my tranny a few weeks ago he said the clutch looked fine. So what would cause a vibration at a given speed only to go away and return at double that speed?

 

[03ghoststang]

well i had a friend who had that at around the same speed and we put an aluminum drive shaft and it went away........

maybe your D/S is out of balance slighty

 

[Kilgore Trout]

Vibration at 55-65 only is a classic sign of an imbalanced tire. Tires can quickly go out of balance, especially if they are not genuine Ford rims.

 

[COramprat]

Vibration at 55-65 only is a classic sign of an imbalanced tire. Tires can quickly go out of balance, especially if they are not genuine Ford rims.

Nah...I know what tire shimmy feels like. This isn't in the wheels/tires. It has been there with my old tires and now the new ones that I just had mounted. Definatley in the driveline somewhere. BTW...I have Genuine Ford Rims...take offs from a Mach 1.

I was thinking since it happens at 65 and again at 125 that it has some kind of resonance factor. ???

 

[COramprat]

A thought struck me...Pinion angle. The vibration started after my clutch swap but it is also when I swapped springs. Anyone know how to set the pinion angle?

 

[03ghoststang]

A thought struck me...Pinion angle. The vibration started after my clutch swap but it is also when I swapped springs. Anyone know how to set the pinion angle?

for pinion angle i believe you will require adjustable upper control arms to set it in

 

[joshheat25]

Well the Vibration you are feeling is the driveshaft! I have 4.10's as well and once I get up above 65 I can feel alot of vibration. Especially when you let off the gas! A good test is to go about 80-90 and let off the gas and you will hear a humm which is your driveshaft reaching the resonant frequency causing Resonance. At certain mph your drivshaft is spinning at the right speed to create Resonance which is (where the humm is the loudest). It's def your driveshaft.
EDIT: Get an aluminum driveshaft.

 

[COramprat]

I already have an aluminum DS...I'm thinking it has something to do with lowering the car. Something is just a little out of whack.

 

[Mike97gt]

I think your on the right track with your pinion angle idea.. Do you have adjustable upper control arms? you can also put shims in between the trans mount and tranny.

what you will need to set this is a drive on lift, a angle finder and a straight edge.

here is a pic that might help describe what you need to do..

also here is a link describing what you need to do..

http://www.carcraft.com/howto/91758/

View attachment 418579

 

[joshheat25]

Well that throws that idea out the window that it's the driveshaft itself... but you should check everything along the drive line...and Yea.. hmmm never thought that lowering a car a few inches could destroy that angle and cause balace issues... hmm svttech76 has a good point and that article does also. You might want to check that out as well good luck finding the problem. I have to do this as well but I'll prob end up buying a aluminum driveshaft and still have vibrations.

 

[46gtsblown]

http://www.tccoa.com/articles/tranny/transmission/page17.shtml[/url]

This has a lot of good info on driveline vibes.
Good luck.
ps is your harmonic damper installed on the diff? If not reinstall it, I removed mine after a gear change and the vibes were horrible reinstalling it cured my problem.

Dwayne

 

[COramprat]

http://www.tccoa.com/articles/tranny/transmission/page17.shtml[/url]

This has a lot of good info on driveline vibes.
Good luck.
ps is your harmonic damper installed on the diff? If not reinstall it, I removed mine after a gear change and the vibes were horrible reinstalling it cured my problem.

Dwayne

Referring to the "dogbone"? It is still there.

Mike...thanks for the info. I am almost positive that is it. It is funny that it occurs at 60 and reappears at 120 (we have a track with a VERY long cool down lane ). That is why I was wondering about resonance.

 

[COramprat]

Another question...

I had this clutch vibration/chatter when I got the car back after the tranny fix. Once it is disengaged it goes away. I crawled under today while I was doing my brakes and I can wiggle the clutch fork around a little. Once it is running it vibrates and makes a chattering noise. Sounds like on of those electric toothbrushes. I can put a little pressure on the clutch pedal and it goes away. Is there an adjustment to make it go away or do I have a problem?

 

[COramprat]

Anyone?

 

[Mike97gt]

adjust the clutch cable so it has a slight tension on it.. your not supposed to be able to wiggle the fork.

 

[03ghoststang]

Another question...

I had this clutch vibration/chatter when I got the car back after the tranny fix. Once it is disengaged it goes away. I crawled under today while I was doing my brakes and I can wiggle the clutch fork around a little. Once it is running it vibrates and makes a chattering noise. Sounds like on of those electric toothbrushes. I can put a little pressure on the clutch pedal and it goes away. Is there an adjustment to make it go away or do I have a problem?

do you have the cluth cable adjuster?

 

[COramprat]

do you have the cluth cable adjuster?

Yep...I'll try to adjust it and see if it helps. What would be the problem it the fork moves around? A bad one?

 

[COramprat]

Bump

 

[fast97gt]

um i have my ride lowered almost three inches and the caster camber adjusters for the front they werent enough had cut slots in the strut bolt holes were the spindle and all mount but my point is i dont have any vibs