I recently experienced a failed silentbloc. It seemed important enought to
share the reasons why this occurred in order to help someone else avoid
this problem.
I was very fortunate. The bush seperated as the car was leaving my
driveway, not during the 120 miles of 60+mph sweeping tree/cliff lined
secondary roads I drove earlier that day. We suffered complete loss of
steering, caused by the seperation of the silentbloc bush on the drivers side.
The silentbloc bushes installed in my car, by the PO, were in good
condition. I had examined them several months ago. The rubber was solid
and they were complete. They were, however, different than what Moss is
currently selling, as I have recently seen their product. The washer on
the top of Moss's silentbloc is steel and thick, perhaps 1/8 inch, as I
recall it. My silentblocs had a copper washer on the top, approximately
1/16 inch thick.
I have some slop in my steering, partially in the steering box but mostly
in the idler lever trunion, which acts as the pivot point for the passenger
side of the steering linkage. There was enough play in the system that the
passenger side front tire was experiencing accelerated wear on the inside
of the tread due to the looseness of the steering and the resulting motion
in the front wheel. There was not a lot of slop in the steering, but there
definitely was some.
The control arm bushings and tie rod ends are tight. Because of the
looseness in the idler lever and steering box, and the fact that I
anticipated pulling the engine, etc., I had decided, based on the slop and
accessability with the apron off, to rebuild the steering box and replace
the idler lever this coming winter.
The bottom line is that there was enough play in the steering system that
the samll bump at the end of the driveway, was sufficient to cock the
steering linkage sufficiently to force the copper washer off of the stud
which held the assembly together. I suspect this weakening or failue of
the copper washer occurred over time, but don't know for sure. I don't
believe this would have occured with the steel washer but, trust me, this
is a VERY scary failure. We lost complete directional control of the car.
The steering wheel was no longer connected to the front wheels.
Check out your silentblocs. It is easy to tell the difference between the
thin copper washers and the steel ones. If you have copper top washers,
consider having replacing them, especially if youi have some slop in your
steering systems.
Although I believe the failure in my TR3 was due to a combination of this
particular silentbloc bush and the slop in the steering system, the copper
topped silentbloc bush is an inferior component.
Keep the rubber side down,
Jack
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