Car shakes Violently @ 1000 RPM

[im2damncool]

The whole car shakes violently at anywhere between 1000-1500 RPM's. No matter what gear it's in. Up until a few weeks ago it's made a loud thunk! noise from the front of the car whenever you stop at a light or sign. Basically whenever there was a signifigant weight shift. Been doing that for a month or two. Now it stopped and the whole car just vibrates. Took it to a shop and they put the sensors in the exhaust and said the emmissions showed no problems. So it's apparently not a vacuum leak or timing or air/fuel problem. I'm thinking motor mounts. Thoughts? I did the test where you put the car through the different gears and gas it with the brake on to see if the engine moves a lot. It seemed to buck more in drive than reverse but I really don't know what's normal movement vs. what's excessive.

 

[91lxttrim]

I would check the motor mounts first.

 

[wht93gtEd]

check for movement in the driveshaft or u-joints.

also, check the tranny mount...they have tendencies to wear out over time.

both of those things are much easier to check rather than the motor mounts at first.

 

[TheBocSez]

Bad U-joints maybe or Harmonic Balancer?

 

[dragnazz5.0]

im thinking motor mounts. take a look at the fan. it should be dead center in the middle of the fan shroud. the shake is probably a combination of things like a bad balancer and the motor sitting on the kmember or directly on the mounts with no rubber in between.

 

[mob]

anyone else think 1k rpm's is alittle low? I may have a bcam, but my car boggs under 1700. I couldnt imagine cruising at 1k. May be the stuff listed above but you sure the car isnt just bogging down?

 

[stang8urimport]

Harmonic balancer

 

[nonglossjason]

mine shakes a little but im leaning to a warped flywheel.

 

[aussie5.0]

i would first check the engine mounts, then the harmonic balancer. Ive seen alot of people replace the harmonic balancer and get a much smoother car to start off with, so its always worth it.