Slight vibration at 3400 RPM????

[bynumj]

I noticed that I am getting a slight vibration feel in the shifter at 3400 RPM. At first I thought it might be the trans or drive shaft but after some testing, I get the slight vibration feel with the clutch in or out, moving or stopped. This only leaves two options: 1) there is a vibration with the motor or pulley, 2) there is a harmonic from the exahust at this RPM. The vibration is there whether the motor is under load or not. The consistant thing is that it only happens at 3400 RPM. This is not a vibration that you can hear or that shakes the car but can be felt through the shifter.

Has anyone else had this feel and what do you all think it might be?

 

[Gearbanger 101]

Does it happen in every gear, or just a particular one?

 

[bynumj]

Does it happen in every gear, or just a particular one?

It happens in 1, 2, 3, 4, N, clutch in, clutch out, moving, or stopped. The only constant is that it happens at 3400 RPM. This leads me to think that it is a vibration in the motor or a harmonic of the exhaust.

 

[Gearbanger 101]

Could be engine harmonics. These engines are kind of thrown together with best guess in mind. The rods and pistons aren't exactly measured to within three decimal places like they are with an aftermarket set up after all. That and the stock balancer aren’t exactly precision built.

If it were a driveline vibration (drive shaft, u-joint, flywheel, etc), my guess is that it should be taking place at all RPM. You might want to crawl underneath and make sure none of the exhaust components are close enough to the floor pan, trans, or other areas of the vehicle to make contact.

You could try swapping out the balancer for a higher end one like ATI, or Innovators West....or even another Ford unit, but unless you know for certain, you might just be throwing unnecessary money at the problem.

Keep in mind...your Hurst shifter won't have the soft, rubber bushings that the stock unit did. It may have very well always been there, but not made itself prevailant until the addtions of the aftermarket shift. They've been known to trasfer vibration from the engine and/or driveline into the cabin.

 

[bynumj]

I am just thinking that if it were an engine vibration that I would have to worry about that it would happen at other RPMs but I am not sure. I just didn't want to have Pop Goes the Motor over something that I could have fixed. I think I will take it to our local Pro shop and have them weigh in.

 

[bynumj]

After deliberation with some of my race buddies, we believe that it is a harmonic caused from the exhaust.