82_930

Hi,

on my 2006 C4, I am noticing that when idling my car vibrates. Do I need new motor mounts? Are there transmission mounts as well?

The car is 10 years old

1) If so, which ones do you guys recommend?

2) If not, what would cause the car to vibrate?

ChicagoSpeed996

My car vibrates at idle. It is lovely! I think that's normal. My 996 also did that. Unless it is excessive. Has the vibration gotten worse over time? Are the exhaust tips significantly lower on one side?

MaddMike

It is a boxer aka flat or horizontally opposed engine. These engines do not require a balance shaft or counterweights on the crank shaft. The engine has a natural dynamic balance which is achieved when in the RPM ranges that the engine is designed to operate in.


On idle, boxers can exhibit a rocking motion--which is part of their charm. I love my BMW motorcycle for this reason.

chuck911

Yes the flat six is an inherently smooth running design. It does of course move, therefore vibrate. But the vibration should not include any mechanical knocking. Worn motor mounts aren't damping like they should and can result in a knocking type vibration. Before they get that bad they could also allow the motor to move around enough to exaggerate the normal vibrations at idle.

Some things to try, do you notice a knock or bump when starting? Or if you blip throttle in neutral? Or driving slow in 1st, if you speed up and slow down (using only throttle no brake)? If you get a knock doing any of those your mounts are shot.

Its the two motor mounts that go. But yes there are two more smaller ones at the transmission. They take much less load and last longer. Its the motor mounts you tend to notice. If you're comfort-oriented go with stock. If you appreciate throttle response and sharp handling- and won't mind a little more cabin noise- get firmer ones. The difference in performance (driving response) is something auto crossers will notice. The difference in noise is something a commuter might notice. Choose accordingly.

user 72902

That's a difficult one to determine without the opportunity to drive lots of different 997's. We get used to what are cars do (sounds and feel) and many problems increase incrementally and we adapt and think it is normal. I cannot advise but I'll tell you that my car was much smoother both running and shifting after I replaced my motor mounts.

82_930

My car's vibration has definitely increased noticeably and shifting gears 5th & 6th... also reverse has been affected.

I could be wrong, but I am thinking that after 10 years my motor/transmission mounts might just be worn out.

I will have to check if there is any clunking sound when I start the engine or when I step on and off the gas.

As far as the exhaust tips being lower on one side, this I can't use as a determination as I had taken out my mufflers and had the Hanksville Gundo Hack done. When taking the mufflers off and then later putting them back on, I had to remove the exhaust tips and when putting them back on, you can adjust the angle of the exhaust tips so I made sure that they were both symmetrical looking (thus making them equal).

I will check them regardless to see if one of them is angled more than the other,but I doubt that I will be able to make this determination.

Thanks for the input.

I am leaning to stock motor mounts, and I know I already touched on this a bit, but does anyone know of a set of high performance ones that they swear by? Something that provides comfort/low noise/and performance?

pavster

If you are sensitive to engine-related vibrations definitely stick with the stock mounts. I recently swapped mine out for semi-solids and am still adjusting. A lot more buzzing in the car, especially around 3k RPM which is where I do most of my highway cruising. It's a bit like being next to a subwoofer vs sitting on a subwoofer - now all the vibrations I used to hear via exhaust come to me via my spine. It's both good and bad. But I may go back to stock mounts. BTW my 7 year old/40k mile stock mounts looked like new when I took them out.

The way you describe your vibration, it might be related more to worn transmission rather than engine mounts.