Original submission by T Feb 21st 2007;
Back to Brakes, Wheels Suspension
Any part of the Suspension or Drive Train that is loose is likely to show up as vibration when the Car is at cruise.
Wheel Balance:If a Front Tyre is out of balance, a periodic pulse will be felt through the Steering Wheel as the Car's speed increases. A Rear Tyre will increase its vibration with speed but not be felt so much through the Steering Wheel.
Toe In:Incorrectly adjusted Toe-in will appear as a vibration that starts when the Car's speed is increased. It may also go away as the Car accelerates faster.
Sway Bars:These are often connected to the chassis by rubber hinges and to the Car's Suspension by rubber Bushes.
The Grommets and hinges will wear out in time. The looseness that results will cause a vibration to occur when the car reaches a certain speed.
If the wear is left for too long, the Sway Bar will wear large holes in the Control Arms.
The fix is to drill out the Control Arms and fit oversize Bushes.
Upper Control Arms:The pivots on these went to rubber Bushes from HT on. When the rubber centres wear out
they will affect the Camber, Castor and Toe-in. The poor Wheel Alignment that results can contribute to vibration.
Lower Control Arms:These used rubber centred Bushes from HT on. The lower bushes will need replacing before the top ones because they carry the weight of the Car on them. Wear in these will show up as Castor, Camber and Toe-in problems all of which can contribute to Suspension Vibration.
Trailing Arms:From HQ and LC on Holden used Trailing Arms on the Rear Suspension. The advantage is that
the Rear Axle was positively located whereas with the previously used Leaf springs the Rear
Axle was not so precisely located.
Off Road drivers often talk about the advantages of Leaf Springs in rough Road conditions.
A Leaf Spring will allow the Rear Axle to move backwards or forwards as required
over an obstruction.
A Trailing Arm provides precise movement around a fixed arc and gives more precise handling on a Bitumen Road. The Trailing Arm also prevents Axle Tramp which caused earlier model Holdens
to jamn in 1st Gear if a high speed takeoff was attempted. Essentially the Rear Axle wound up like a Spring under power. When the Clutch was released the Rear Axle reacted speeding up the
Tail Shaft and causing the Car to Jamn in 1st until the energy was dissipated.
The Trailing Arms use rubber centred Bushes as Pivots. When the Bushes wear looseness appears
in them. Any looseness will cause the Rear Axle to vibrate. The nature of the vibration can
change with the addition or removal of power.
Upper Trailing Links:These can tend to show up problems first because they don't carry so much of the vehicle's weight. They are responsible for stopping torsional reaction in the Rear Axle.
Wear in these can typically appear as a vibration when the Vehicle is Engine Braking in Top Gear at high speed.
Lower Trailing Links:These take longer to produce a vibration but can still contribute. They can contribute to a Rear Axle bang on take off or with power reduction.
Universal Joints:A worn Universal Joint carries danger potential. If a Universal Joint is considered
to be faulty it should be replaced immediately. If the Tailshaft works loose and tries
to fall out on the Road the consequences can be tragic.
A typical worn Front Universal Joint will show increasing vibration with speed and change its reaction under deceleration.
When replacing Universal Joints make sure these are free to rotate before installing them in the Car. If the Front Universal has a tight spot it will cause the Car to shake with each Tailshaft rotation.
Engine Mounts:Engine Mounts can fail if they are left Oil soaked. Any cause of Oil Leak should be investigated and fixed and the Engine Mount washed clean or replaced if it is cracked.
If there is any looseness in an Engine Mount it will show up when the Engine is developing power and also at speed.
Gearbox Mounts:The same rules as Engine mounts. If they show any cracks, replace the Mounts. Fix any Oil Leaks around them.
BellHousing Bolts:There have been instances where incorrect Bellhousing Bolts have been used during an installation.
In some instances a Bolt has been too long and has bottomed out in the Engine block. This has resulted in the bolt being torqued down correctly but not holding the Bellhousing tight to the Engine.
In other instances a Bolt has been too short and has not engaged in the Engine block leaving it loose.
Either way the result is a Bellhousing that is not adequately secured. The undesirable result can be a vibration that occurs when the vehicle is at speed.