Banging sound on floorboard when accelerating up hill

[RSBob]

Dad just got a 968 cab with an auto from his wife for his birthday. Car does everything well but has one annoying problem no one can seem to solve. When doing 70+ uphill (not down hill or on level) there is a banging noise on the floor boards. Anyone ever heard of this?

Here are his words.... at 70 MPH on an uphill stretch, the loud rumbling and vibration underneath is still there. It stops as soon as you take the foot off the accelerator.And on level ground it does not make any noise, even at 80 to 85 MPH.

Dad was born in Germany is 83 and still has a lead foot.

[flash968]

could be a failing flex damper, though you would typically hear a banging on and off throttle, like backlash in the driveline. however, if it is only cracked, and not completely broken, it could do what you are talking about.

could also be a blown motor mount causing interference under load.

is the banging rhythmic? is it limited to or different in any particular gear or rpm point?

[RSBob]

Sent him your question. We shall see. He's in Santa Cruz if there are any local experts that anyone would recommend

[v2rocket_aka944]

Maybe an exhaust mount? Mine used to bang the trans tunnel because the mount was misaligned

[RSBob]

Update from dad: just had both motor mounts replaced (original parts, came from Germany, $600. I don't know what a flex damper is, but will find out from the local Porsche guy here. I just washed the car for the first time and noticed a loose flap behind the left front wheel, which makes quite a noise when banged against the body. Will secure that with a screw and see if it helps. If not, I will consult my guy. The noise and the vibration only comes under full throttle.

v2 - good thought. he had that checked as well and the clearances are good. Thanks

[tamathumper]

Does he notice the noise when your mother isn't in the passenger seat?

[RSBob]

There is constant noise when she is in the car. The fix would cost far more than the car's value. 😺

[tamathumper]

It was worth a shot. I figured if he's 83 years old and doing 70+ uphill, maybe the noise is her banging on the "passenger-side brake pedal"?