Differential Noise - Old Datsun Mass Dampers

[Guest Rick Johnson]

Well not really a "Chevy only" question but I think the real technos hang out here.

 

My car makes a loud ring and pinion noise in the COAST mode which peaks at 45 MPH. (In fact 3 different rear ends have all made objectionable pinion whine in this car!) With 3:54 gears this equates to a pinion mesh frequency of about 380 HZ. I verified the diff is vibrating at about 380 HZ with an FFT analyzer when the noise is peaking. In an effort to determine which part is acting as my speaker, I attached an FFT's accelerometer to a variety of under car parts and banged around with a hammer. Sure enough the mustache bar's natural frequency is about 380HZ, so I figure this is the part that is being excited, resonating, and sending the noise throughout the car (nothing else was even close to 380HZ).

 

I could probably hang some weight on the bar or stiffen it somehow but I am looking for a shortcut or some tribal knowledge here at HybridZ. I have heard that the old 240's had some weight attached somewhere to the differential that Datsun used to dampen ring and pinion noise.

 

Does anyone have any knowledge of this weight or personal experience with removing / installing this weight for noise reduction???

[Pop N Wood]

Maybe related to this thread

 

http://www.hybridz.org/ubb/ultimatebb.php?ubb=get_topic;f=7;t=001306#000000

[Guest Rick Johnson]

Thanks for the link to that thread. He referred to several plates mounted directly to the front cross member of the 78 vintage Z's. I will keep my eye out for such a mass damper and try them. Anybody have some for sale?

 

I also heard of, but have never seen, some weights that supposedly look like balls of some sort. They may not have been standard equipment but may have only been used for complaining customers back in the early 70's.

 

Has anyone seen or heard of these ball type weights or any weights that were used in the early 70's cars??? I would like to buy some and give them a try if they exist.