I decided that after my recent front end issue, I would compile all of the knowledge I had searched for across the Web and any experience I had personally gained. Attached is a zip with the docx format, and below is a link:
Unfortunately, I could not get the file size down enough to meet the forum max (which is low!)
TOYOTA TACOMA FRONT END VIBRATION TROUBLESHOOTING GUIDE
This guide is created for diagnosing and solving front end vibration issues. A decision tree will be established to aid in a root cause analysis.
IDENTIFYING THE GENERAL SOURCE OF THE VIBRATION
Vibrations can be caused by suspension, steering components, drivetrain, or the wheels and tires amongst other things. This section will aide in determining individual components to investigate.
Is the vibration dependent on vehicle speed?
When vibration starts, slow down or speed up and observe the results.
Is the vibration dependent on engine speed?
When vibration starts while moving, put the vehicle in neutral and observe effects. Additionally, when vibration starts, place vehicle in neutral and then shut off the engine and observe effects.
Does the vibration occur when turning as well as going straight?
When vibration occurs, turn the wheels and observe effects.
Does the vibration occur when braking?
Let the vehicle roll at low speeds and feel and listen for any brake grab while the wheels turn. Also, at speed, brake hard and feel for any vibrations.
Once you have determined the probable cause, refer to the appropriate section for further diagnosis.
I have little experience in this realm, so this is not as detailed as it should be.
Referring back to the results of the tests in the previous section,
Did the vibration stop when you put the vehicle in neutral while moving?
If so, the problem likely lies between the flywheel and the drive wheels. Drive shafts and axle shafts are the two rotating members in this region, and will be susceptible to oscillations more than anything else. Visually inspect the driveshaft and axles for physical damage. Then you may need to test their rotational balance.
Did the vibration stop not in neutral, but when you cut off the engine?
Something from the flywheel forward must be out of balance. There are lots of moving parts in an engine, but an extra vibration can be nothing but bad.
While the vibration is occurring, try putting the vehicle in four-wheel drive (if you have it). Does the nature of the vibration change?
If so, you may have a problem with your front CV joints or half shafts.
NON-DRIVETRAIN COMPONENTS (INCLUDING STEERING)
This type of issue can be the hardest to nail down, as there can be multiple sources of vibration.
The first step should be a simple test to know whether you should pursue wheels and tires as your cause of issue, or suspension components:
1. Lift one side of the vehicle until the front wheel is no longer touching the ground.
2. Grab the tire on the horizontal axis (hands at 9 o’clock and 3 o’clock) and try to apply torque to the wheel (pull from the left, push to the right, and vice versa). If there is significant play, you may have a steering issue. Please look down the page for another steering test.
3. Grab the tire on the vertical axis (hands at 12 o’clock and 6 o’clock) and apply torque to the wheel (pull from the bottom, push the top, and vice versa). If there is significant play, you may have worn upper or lower ball joints. You may wish to have these inspected by a mechanic because worn ball joints can become a safety issue if allowed to fail.
4. If you fail to find any play for either Step 2 or 3, then you most likely have a problem with the wheels and tires.
WHEELS AND TIRES
Here are some easy things to try for starters:
-Adjust tire pressure: many truck tires are sensitive to excessive pressures than can cause them to bounce along the road
-Rotate the tires: sometimes the tread may wear in an uneven pattern, causing vibrations on the more sensitive front end. Simply moving the position of the tires may allow the fronts to wear in to a smoother pattern on the rear.
-Balance wheels: over time, the tread and structure wear of tires may change their rotational characteristics. Also, wheel weights may fall off or the wheels themselves may slightly deform. Getting a proper balance (on a Tacoma, this is a lug-centric road force balance) can smooth out any wheel rotational tendencies.
If any of those solved your problem, superb! Otherwise, you should look into suspension or the additional steering system test described below.
If you suspect any play in the steering system, you should test for worn bushings. Typically, a rack gear will last over 150,000 miles, but the rubber bushings used to hold as well as isolate the rack/crossmember interface can wear out well before this milestone. For this test, you will need a partner.
Have your partner sit in the vehicle with the key in to keep the wheel unlocked, but with the engine off. Instruct your partner to rotate the steering wheel back and forth. Do you notice any of the rubber bushings deforming or moving in their mounts? Is the steering rack moving significantly in any direction?
If so, the bushings may need replacing.
Note: this is also a good opportunity to inspect the state of the steering system. If the tie rods seem loose, they may need replacement. Also, check the steering rack outer seals by unclamping the outer clamp of the bellows covering the inner tie rods and check for fluid leakage. If there is leakage, the rack will be to be rebuilt (or replaced ).
I recommend the Energy Suspension bushing kit because the bushings are made from high quality polyurethane and will not only last longer but yield a more firm performance from your steering system.
DiscountSteering.com is where I purchased my steering rack, their prices are competitive and they allow a return shipping label (for the core) to be added to your purchase for just $12. I have seen no issues with their quality.
Occasionally, a vibration may develop because a suspension strut is unable to dampen any oscillations the wheels may be undergoing. This will develop after years of use, and there are simple test you can perform if you suspect your struts may be worn. The following is taken from the ehow.com strut testing guide:
1. Perform a "bounce" test. Put your foot or knee on your front bumper and push down with all of your weight as low as you can push it toward the ground. Take your foot or knee off. A car with good struts should rebound quickly. Perform the same test on the back bumper. If your vehicle bounces up and down more than twice, your struts could be worn.
2. Perform a driving test. Drive through an intersection or dip in the road. If your car makes strange noises or thumps or bounces three or more times, your struts might be worn.
3. Visually inspect the struts. Touch the towers of the struts, and look for signs of damage including the presence of a leaking oily liquid and caked-on dirt from the road. If your struts are leaking, they are damaged. The only remedy is replacement.
4. Take your vehicle to a mechanic if you still have doubts. Ask the mechanic to perform a visual inspection and drop test. A drop tester drops the vehicle one axle at a time from about 10 inches up in the air. It then plots a graph of the vehicle's suspension reaction. This should determine whether your struts are worn.
If any of the test procedures yields a result that is suspicious, especially if you have not replaced your struts in a long time, then you should consider strut replacement.
Ball joints attach the wheel assembly to the A-arms and upper suspension. They allow the wheel to move up and down while still remaining attached. Both lower and upper ball joints can wear out and fail. However, prior to failure, if they have worn and do not fit firmly then they can vibrate in their mountings. When inspecting the ball joints, on first generation Tacomas, also take the time to inspect the bolts attaching the ball joint to the A-arm. These have been known to fail, and losing a wheel while driving is a genuine safety concern.
Ball joint replacement is not a beginner level task, and a Haynes or Chilton’s guide would be a very helpful resource (as always).
Warped brake rotors can cause vibrations for two reasons:
1. A warped rotor presents an off-balance rotating mass
2. A warped rotor may contact the brake pad during rotation and momentarily slow the wheel down. This contact may cause a vibration at high speeds.
There are several quick ways to test if the rotors might be warped:
1. While rolling at slow speeds, listen and feel for any contact during each rotation. There may be a metal on metal sound or you may feel the vehicle pull slightly while rolling.
2. While at higher speeds, press the brakes hard and feel the pedal and steering for any vibrations. Uneven braking may indicate warped brakes.
3. Jack up the vehicle in your garage, and remove the wheel. Take a straightedge to the surface of the brake rotor and look for any gap underneath the straightedge. NOTE: Resurfacing brake rotors will not repair warping.
Hopefully this guide has been helpful to anyone trying to diagnose a front end vibration. If you have any questions or wish to add to this guide, please email me at firstname.lastname@example.org