2000 Pontiac Grand Prix shakes at 45mph

Another question regarding the shaking would changing the spark plugs help at all?

I just had the tires replaced and balanced changed the plugs and wires. Changed the air filter and oil. But still shaking when I get to 45mph. So im stuck and confused?

There is no lights coming on. Its defiantly coming from the front end, I just cant figure out where, I defiantly feel it from the steering wheel. It can start from as low as 35 but starts to smooth out a little at about 70. I have heard so many different reasons, so any good advice is good advice. I love the car so I will be putting allot of effort into it.

I think it may be the Motor mount or the balance shaft is off.

I have the same problem, Im going to get it looked at this weekend

The motor mount? I have heard that before but I cant locate it. And the balance shaft? Where its that? So is your shaking progressive or does it always start at around the 40 45 area?

Mine comes and goes, its not always constant, and its not a violent shake.

I know I need an alignment too, but it shake more when I turn the wheel to the right, but the shake feel like they are coming from the front centre and not from teh wheels, feels likes its right under the gas pedal.

Im going to do the tie rods and alignment this weekend. So I will know more from there.

I did research on the motor/engine mount, and found it stop the car from shaking, when the enigine is shaking (running). Motor mounts support the engine and transmission, and dampen noise and vibration. The mounts isolate engine and transmission from the chassis so vibrations and noise are not transmitted to the rest of the vehicle.

Aa1car. Com/library/motor_mounts. Htm
wiki. Answers. Com/Q/What_is_a_motor_mount

Balance shaft.

In piston engine engineering, a balance shaft is an eccentric weighted shaft which offsets vibrations in engine designs that are not inherently balanced.
En. Wikipedia. Org/wiki/Balance_shaft

A shaft designed so that, as it rotates, it vibrates in a way that reduces or cancels some of the vibration produced by an engine. Not essential to an engine's operation, balance shafts are nonetheless becoming increasingly common as a means of engine refinement.

A single balance shaft is used when fitted to three-cylinder and V-6 engines. Four-cylinder engines use two shafts turning in opposite directions on either side of the engine's crankshaft

autorepair. About. Com/library/glossary/bldef-022a. Htm

trick now is just finding out what is the actual problem :S