morepar

Hope some one can help me identify the purpose of a chassis dampner?? under the floor of my 1973 Satellite/roadrunner. What it is , is a large hunk of cast iron (about 20 lbs) and rubber mounted to the under side of the floor. It's around a foot long and 3 inces wide. It's mounted by 3 bolts to the top center of the floor hump and hangs down the sides of the drive shaft an inch or two. Definately not around the drive shaft enough to offer any protection from a broken shaft. Cause of the weight and the rubber mounting I figure it to be some tyype of dampner. Can't figure out what purpose it possibly serves. Part number on it is 3466722-1. Thanks for any insite offered.

Gorts 5th

sounds like a trany damper
does it look like this. mounted to the end of the tail shaft

CJD AUTOMOTIVE

Dampeners are still used on brand new cars. The are to change the frequency of a part. Every part on a car has a frequency in Hertz, and also a free resonate frequency. Think about the old commercial where the opera singer hits a note and the glass shatters. The note she hit has the same frequency as the free resonate frequency of the glass. Free resonate is when a part cycles uncontrollably. If you hit the free resonate frequency of a part on a car, this can cause anything from a drone to a bad vibration. The engineers purposely design parts so that they have different frequencies from one another, but what is designed and what makes it to production sometimes differs, and they end up with a vibration. Rather than re-engineer a part, that add "mass dampening". Add weight to a part and it changes it frequency, and no more vibration.

Sorry, long winded.

440roadrunner

Actually a pretty fair explanation, considering that entire walls full of books have been written on wave action and harmonic vibration.

It is also important to realize that it was the ORIGINAL drivetrain that needed this. A different weight/ size (diameter driveshaft), different rear axle, or different engine combination will change the dynamics, and might just make this device either ineffective or useless.

Also some manufacturers such as Mercedes experimented with sound dampening by using an amplifier in the car to actually amplify NOISE. This is applied "out of phase" with the unwanted noise you hear in order to cancel it.