[Geronimo '74]

First of all, I did use the search button and I found out a lot about vibration issues. But my mystery is not solved.

Here's what's wrong with my car as far as I can tell. It takes in false air between intake and cylinders. So I need to replace those gaskets . My gearbox (915) needs a rebuild. and my front tires are unevenly worn due to a bit to much neg camber.

Here are the symptoms. When I drive, no matter the speed, I hear a low tone growl front and left. Like I'm running an off-road tire there. A higher speeds ( 80, 90, miles an hour) the growling noise gets louder and I also feel an oscillating vibration, off and on for a few seconds. It is noticeable on the passenger side, next to the wheel-well. But also in the gearstick, in the steering wheel..

At first thought, I would say the wheel bearing. Did the test of swaying from left to right, to see if there's any difference in noise. No difference in noise, so I ruled out the bearing issue.

What is more is that I noticed that the speedeometer needle is bouncing a little bit in the same oscillating rhythm as the vibration. It goes down about 5 to 7 km/h and then goes up to the correct speed again, all in the same rhythme as the noise. (Well maybe not exactly synchronous but it is obvious they are linked somehow.)

So now I'm thinking gearbox... because of the bouncing speedometer needle. Can gearbox issues cause this type of vibration as well?

A friend mechanic drove it and he did not think it was a bearing issue but frowned when I asked if it could be a gearbox issue.

Any comments, thoughts, directions would be very welcome.

Thanks you guys.