Seeking material engineer/plastic guru wisdom

Long story short: I have a custom short shifter in my 6-speed manual truck that resonates transmission noise into the cab via the shift knob. Without a shift knob on the shifter, the setup is virtually silent. With one on, 6th gear gets to me during long highway drives.

I am a machinist by trade. I've tried turning a few different materials, such as: brass, aluminum, UHMW, and Delrin but haven't found a solution for dampening the sound. So far, the stock leather wrapped knob (with presumably nylon threads) seems to offer the most suppression.

Anyone have any recommendations for materials or other possible solutions? I love the shifter otherwise so I'd rather not change it.

 

Curious, would some sort of rubber washer do the trick? Get it between the shaft and the shift knob and the knob then won’t vibrate?

 

No dice unfortunately. Just gave it a try.

 

damn, no idea then, sorry

 

I'm not an engineer, but it seems like it is related to the length of the shifter. That length is causing it to vibrate at a resonant frequency. Changing the weight of the knob on the end won't do anything. If you make it lighter it might do it less, but it will still be there. The only solution is to make its "effective" length different. Putting something on the shaft may work. I would try making a rubber bushing that you can move around on the shaft. That way you can essentially "tune" it. Once you find the positioning you can make it out of something nicer.

 

Guys with buzzy Hurst shifters use Dynamat...