Engine/Transmission (1994 - 1998) Drive shaft has a "harmonic balancer" on it - why?

[Dan_69GTX]

My 96 Dodge truck, 4x4 5spd has a harmonic balancer looking thing on the front of the driveshaft. Anyone know what it is for? Why is it there?



I say harmonic balancer cause it is approx 1. 5" wide, 7" diameter, and is attached to the front yoke via a rubber insulator - similar to a harmonic balancer.



How often do these move?



I'm asking cause I have a vibration at 72-78 MPH. I believe it to be the driveshaft since it the vibe is there with the vehicle on jackstands and no tires or brake drums. But it is not there with the driveshaft removed.



Any ideas?



Can this "harmonic balancer" be removed?



How hard/expensive is it to balance a driveshaft?



Thanks!

Dan

 

[jimk]

vibration

I would think that the reason is for damping of a resonance freqeuncy. There are a couple of ways that I have used to get by in balancing a drive shaft. I have used a couple of hose clamps to add a weight the shaft and drive the truck and see if there is a change. Move the clamps to change the vibration. You can even add a wheel weight to add the amount if needed.

I would check for looseness in parts, worn yoke or bushing in the drive shaft. Drive shaft phasing and run-out.

Where I work at we have a data on all of the critical equipment that has vibration recorded on a pm and when there is a work order generated to check the vibration of also. That way you can look a trends. Running equipments till it fails is not all-way cost effective JimK

 

[C Schomer]

The heavy ring is to smooth out the driveline. My 97 doesn't have one. Try blocking the truck up securely and run it while someone watches underneath. I had a van that got a vibration and I ran it on a rack. Everything looked smooth as it could be. Turned out it was the tires but it sure wasn't visible on the rack. Craig