Those that have the hydraulic throwout bearing as offered by HVDA may
find this interesting. Many were wondering as to what happens to the
setup clearance between the clutch fingers and the face of the throwout
bearing, after the initial setup is made. This .100 to .125 clearance
disappears, once the clutch fluid activates the bearing forward. This
was confirmed by McLeod Engineering, the chief designing outfit behind
the hydraulics used in this conversion.
The purpose of the initial clearance is to ensure that there is room for
the t/o bearing to move back, as wear takes place over the life of the
clutch disc lining. It is NOT to give space between these parts during
clutch engagement. McLeod says that there is no problem if this bearing
turns, due to the clutch touching it when fully engaged. The bearings
are designed for 15,000 hours of service. (That is more miles than the
typical lining life of a clutch disc)
It is not unusual fo the clutch fingers, as used for the Triumph
pressure plate, to be of uneven "stick out". Apparantly this can happen
during the heat treating of the pressure plate. When only some of these
fingers touch the bearing, it can barely rub against the bearing and set
up a chirp, or squeal. This sound is not particularly new to those who
have gone thru this with other bearings. The difference is that this
sound goes away, rather than get worse.
Most owners who have installed the hydraulic bearing never heard this
chirping. Possibly because whatever Pressure Plate they used had uniform
fingers. Those that are uneven will eventually wear down their "high
spots". If you use a P.P. that shows this unevenness of fingers, know
that this can be rectified thru the use of a 3 inch sanding disc and a
drill press. I happened to do this because I installed a used (grooved)
P.P. and this returned the fingers to as-new, tho slightly thinner.
Finally, as the grease that's packed into the new Toyota bearing thins
out, thru heat or thru wear, the noise is said to stop without doing
anything! Some will be glad to know that.
Dick Taylor
NFI in any of this.
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