Multi Link Front Suspension - Diagnostic Misconceptions
MODELS: All Q45 (G50)SECTION: Front Axle
CLASSIFICATION: FA94-002
BULLETIN NO.: IBT94-019
DATE: March 10, 1994
Q45 (G50) MULTI-LINK FRONT SUSPENSION: COMMON DIAGNOSTIC MISCONCEPTIONS
APPLIED MODEL: Q45 (G5O)
APPLIED VIN/DATE: ALL
SERVICE INFORMATION:
The Q45 (G50) Multi-Link front suspension has many unique characteristics. The Upper Link Assembly, in particular, displays some characteristics which may be misunderstood and, consequently, the assembly could be misdiagnosed, leading to unnecessary repairs or replacement of parts. The information presented on the following pages of this Technical Bulletin addresses some of the more common misconceptions about the Upper Link Assembly.
For additional suspension noise diagnostic information, refer to 1TB94-018 (FA94-001); "Q45 (G50) SUSPENSION NOISE DIAGNOSTICS".
COMMON BELIEF:
Movement in the Upper Link Assembly is due to worn bushings.
FACT:
Movement in the Upper Link Assembly is generally not due to worn bushings, but is normal. The Upper Link Assembly has a free play specification of 5 mm, as described in the Q45 (G50) Service Manual. The measurement, as detailed in the Service Manual, (Figure 1) should always be used to evaluate Upper Link free play.
COMMON BELIEF:
A "clicking" noise from the Upper Link Assembly that can be produced by applying a back and forth force to the Upper Link/Third Member joint with the vehicle on the hoist also produces a "Rattle" or "Click" noise while driving over bumps.
FACT:
This "clicking" noise is only produced with the vehicle on the hoist. With the wheels on the ground and the suspension loaded (even considering suspension travel) this noise cannot be produced by the Upper Link Assembly.
COMMON BELIEF:
It is common for the Upper Link bushing to wear resulting in excessive free play that requires Upper Link Assembly replacement in order to repair.
FACT:
Although new Upper Link Assemblies have very little free play, it is normal for the free play to increase shortly after installation and then remain fairly constant thereafter. This increase in free play shortly after installation is a normal characteristic of the Upper Link Assembly and does not affect vehicle handling.
COMMON BELIEF:
It is common for the Upper Link Assembly to be the source of suspension noise while driving over bumps.
FACT:
It is very rare for the Upper Link Assembly to be the root cause of customer complaint noises. In almost all cases the actual customer complaint is the result of some other suspension or chassis component.
In general, the Upper Link Assembly.
^ rarely requires replacement due to excessive free play
or
^ is rarely the root cause of customer complaint concerning suspension noise.
Therefore, replacement of the Upper Link Assembly is generally not necessary.