Tracing Vibrations

Many people suffer from vibrations, in this section I will provide some tips and suggestions for finding that illusive vibration. Vibrations come in two basic types, these are the vibrations from moving vehicles, and those from static vehicles both can be troublesome and many are easily found and rectified.

Static vehicles suffering from vibration are somewhat easier to find, so it generally needs the engine running to diagnose them, so begin by running the engine and listening for the area from which the noise is coming from. Most vibration noises are from loose items such as tin ware used as protection plates, or loose components which work loose through off road usage or snapped bolts or studs on moving components such as power steering pumps, fans, water pumps, or alternators.

Begin by running the engine at idle, if the noise is a tinny sound it is most likely some form of tin ware, some noises may only be diagnosed through revving the engine while the vehicle is stationary, and listening to highlight the area the noise is coming from. Check all the underbody, and other protection plates for tight bolts check the exhaust for any heat shields which may be rotten, or have rotted bolts, and check for any damaged items which may be hitting the underside of the vehicle. Check any engine components which may work loose such as hot air ducting pipes or any attachment or mounting bracket which holds another part or component.

Vibrations which are engine speed related can be any reciprocating part, begin by checking the tension of drive belts to power steering pumps, alternators, air conditioning compressors, and water pumps. Slacken off and remove all the belts and check the crankshaft pulley for any movement or out of round, then check each driven item in turn, particularly the pulleys for true and play, and ensure each item pivots correctly. If they do not pivot correctly it could be a loose, corroded, or snapped pivot bolt which is causing the problem.
If an item has any potential defect or play then suspect it, fit drive belts back one at a time and run the engine each time a belt is refitted, if the noise disappears, then reappears when a particular drive belt is refitted, you have the suspect item. If no reciprocating components are showing signs of being defective it could be the clutch, check this by removing the rubber from the clutch actuating fork in the gearbox bellhousing and look inside with a torch, you will see the clutch mechanism. Turn the engine by hand using an accomplice, you should see most forms of damage to the clutch and its mechanism as well as any missing bolts; you can also check the thrust bearing for play using a long screwdriver.
If you still have a vibration you need to look at the engine, if it has excess movement while idling it is most likely deteriorated or broken engine or gearbox mountings, so check these individually. Use an accomplice to rev the engine to see if this movement is excessive when the engine is revved, if you are not sure then compare your engine movement to another vehicle of the same type which is I good condition to make a valid comparison.

Vibrations when a vehicle is moving are much harder to diagnose, these cam be broken down into the main moving components, check when the vibration occurs, which drive set up is engaged, and if it is in one of these or all of them. If a problem occurs in two wheel drive; it is most likely at the rear or in the rear transmission, if it happens only in four wheel drive it is most likely a defect in the front transmission.

Begin with the obvious, check the wheels for any debris which may have collected on them, lumps of mud or cloying clay often stick to the inside of a wheel and throw it out of balance, also check the wheels are tight and none of the wheel balance weights have become detached. Check the tyre treads for any large stones lodged inside them, or a cluster of smaller stones in close proximity, this may be enough to throw a wheel out of balance if there is sufficient weight to an individual, or cluster of stones. Check the tyre tread for damage, if a portion of the tread, or any cleats have become detached from the tyre during off roading it is most likely the wheel is out of balance.
Check the brake discs for any debris in them, it is common for stones or debris to fill a vented disc and throw it out of balance, also check the brake callipers for tightness. While the front end is in the air check for play in axle bearings, or the drive shafts and their CV joints on models with this type of front axle drive arrangement, also check their mounting bolts where they have drive flanges, missing bolts will cause an out of balance. Where front drive shaft arrangements are used check the driveshaft for any damage which has bent them as this will show up as a vibration, also check the bearings on the differential unit where the drive flanges exit the differential.
Where automatic hubs are fitted, it would be prudent to ensure they are engaging and disengaging correctly; abused or incorrectly maintained hubs may not disengage correctly leaving an imbalance in one side of the front axle drive train.
Check the steering assembly for any play in the various joints, if this is slight then greasing them may solve the problem, any play in the steering joints will be exacerbated to a vibration when the vehicle is moving.

Check both propeller shafts, the most common item to wear is the universal joints, if these are not worn then check the splines for any excessive wear, also check for a slightly bent propeller shaft, also check both differential input bearings for play or wear.

Check all suspension components for wear, it is not uncommon for suspension bolts to corrode or snap over time, and suspension bushes to wear or deteriorate; and on leaf sprung models, an individual leaf to snap. On independent suspension set ups it is not uncommon for the end of a coil spring to snap off and impede the suspension while it is working.

Be methodical, work to a logical sequence and check the obvious first, work to a system of diagnosis which identifies what type of vibration it is, and where on the vehicle it is coming from. Remember a fault may not be obvious, and never be surprised what you will find, so check everything and do not overlook or dismiss anything because it is highly unlikely.