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What kind of upper mounts? Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 23 Jan 2008 05:26:13
In Reply to: OK....so how much vibration is normal w/autobox, Aerob, Tue, 22 Jan 2008 20:39:06 Members do not see ads below this line. - Help Keep This Site Online - Signup |
What is the upper mount (dogbone, torque rod) bushings made of? Are they rubber or plastic? Rubber is stock; many folks install plastic (poly) bushings because they can be installed as two pieces. The poly bushings transmit more vibration. If they're rubber there should be an air gap in there, with just two rubber pieces connecting the inner and outer portions (some folks 'fix' the bushings by injecting them with rubber). Also, those two connecting pieces should be approximately top and bottom on the front bushing, and left and right on the aft bushing. So as the engine moves forward and back, the connecting pieces flex instead of going into compression and tension.
Every engine is different, and some vibrate more at idle than others. So with some engines that are pretty smooth, poly bushings don't have that much vibration to transmit. Other engines shake more, and even stock rubber bushings have to work hard to damp it out. So 'poly bushings are great' or 'poly bushings are lousy' depends on the individual engine.
Also, the stock lower bushings are hydraulic. Some folks install solid bushings, either to save money, or to control engine movement for better shifting. Solid lower bushings will also transmit more vibration.
Whats the idle speed when you feel the vibration, and how is that compared to when the car is warmed up? You might just be feeling a resonance. If so, you could try and change the idle speed (not easy), or change the resonance. To do that, sticking a piece of rubber into a stock rubber upper mount may do the trick; yes, more vibration, but if the resonance point is moved, you may not notice it.
So far I haven't answered your question. Normal varies, and it depends on your threshold. When the steering wheel bounces like a paint-shaker, it's too much. But it wouldn't be unusual to feel a bit more vibration when the car is cold and in idle. If you have non-stock motor mounts, there will be more vibration.
posted by 192.249....
, Wed, 23 Jan 2008 05:26:13 <-- Viewing This Message
, Thu, 24 Jan 2008 22:21:58
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