Why does my car shake?

Question

We have a 1982 BMW 320i. Between 35mph and 43mph the car shakes pretty bad. But ONLY between those two mph. I have hear it is a stabilizer bar, a stabilizer bushing, a sway bar. . . . I am so confused. Does anyone know what is making our car shake and why only at that speed? Thanks in advance.

Answer 1

It's not a stabilizer bar or bushing. Those things have nothing to do with speed and don't cause shaking. It's something that spins, like a wheel or the driveshaft. You might have lost a balance weight on the wheel or have a bad tire.  

Answer 2

Likely culprits (from most to least likely)

1. Worn / out-of-balance tires

2. Bent wheel / wheels

3. Bad wheel alignment

4. Bad wheel bearings

5. Thrust-Arm Bushings (sometimes called upper control arms)

6. Tie Rods

7. Warped Brake Calipers

You can check 1 by eye, if those tires are more than 10 years old, then you gotta replace them. Check 2 with a friend, have a friend carefully look at the wheels while the car is in motion, if the wheel shimmys around it will be fairly obvious. Check 3 by letting the wheel go while the car is in motion, if the car tracks straight its not that. (4) Bad wheel bearings are common, check them by jacking the car up and moving the wheels, it shouldn't be notchy or difficult to move any of the wheels, also the wheels should only ROTATE (not move side-to-side or more technically translate). (5,6) I'm not sure how you check tie rods, upper control rods, but I'm sure if you get to that point it may be time to ask a mechanic. (7) Warped brake calipers are obvious also on braking, if you brake and the car vibrates a lot, chances are you're brake calipers are bent.

Resonance is like a swing, if you force something with the right rhythm (like when you're going 35-43mph) you'll get massive displacement (i.e. the car vibrates). Same deal with the swing, if you push someone when they are already at the top of the swing, not much is going to come of it, but if you push someone when they are near the ground, they will go higher and higher...

Answer 3

Have the ball joints checked

Answer 4

bad u-joint, tire out of balance, bad wheel bearing. take it to a reputable shop.

Answer 5

Could be a bad tire, a tire or tires way out of balance or the driveshaft is out of balance, could also be a bad u-joint that is loose or binding.  Driveline vibrations occur between 28-40mph so that is a good possibility.  

Answer 6

k i have a 2007 truck.

and my front tires were kinda bad from driving crazy

and my FRONT ALINEMENT WAS OFF

got that fixed and my truck quit shaking.

just go have ur alinement done for like 40 dollars it should run smooth.