To TR6 & Triumph Lists:
I helped a friend fix (we hope) a sticky clutch in his TR6 over the weekend.
The cause appeared to be a rough release bearing sleeve, sharp edges on the
sleeve and a rough gearbox front cover.
A second problem was that the clutch had a constant squeal when engaged. A
light pressure on the clutch pedal caused the squeal to go away. We had
surmised that the squal was caused by the release bearing rubbing against
the clutch diaphragm spring. Upon examination we found what appears to be
excessive wear on the diaphragm spring. The clutch is the TRF "Magic
Clutch" kit with 5,000 miles on it. A photo of the pressure plate and
photos of the Toyota and standard release bearings are shown at:
http://www.nextek.net/BuckeyeTriumphs/ToyotaRB/ToyotaRB.htm. At this rate
of wear, the spring fingers will be gone in 25,000 miles or less.
The Toyota release bearing seemed to be OK. It is much larger than the
standard bearing. It turns smoothly but is much stiffer than the standard
bearing. The standard bearing spins easily and will continue to spin after
the spinning torque is removed. The Toyota bearing is much too stiff to spin
freely.
We concluded that the light force exerted by the spring in the slave
cylinder holds the bearing against the pressure plate with sufficient force
so that the standard release bearing rotates with the pressure plate. Since
the Toyota bearing has a much greater mass and is stiffer, the force holding
it against the pressure plate is insufficient to transfer enough torque for
it to spin. Hence, the stationary release bearing held against the rotating
pressure plate causes the squeal and excessive wear. We applied grease to
the front of the release bearing as a temporary fix.
Two possible permanent solutions are:
1. Pull the bearing back from the pressure plate when the clutch is
engaged.
2. Apply more force to the release bearing when the clutch is engaged so
that it spins.
Some months ago Scott Tilton posted a couple notes to the list describing a
similar squeal. He cured the squeal with solution 1 using an adjustable
push rod between the slave cylinder and clutch operating shaft arm and a
return spring, an arrangement similar to that used on the earlier TRs. I
contacted Scott yesterday and he said it is still working after the trip to
Breckenridge.
The main problem I see with solution 1 is that the push rod will have to be
adjusted as the clutch wears. A second possible problem is that float is
introduced between the slave cylinder and the pressure plate, an area of the
system that is intolerant of float.
Solution 2 seems the best choice and can probably be achieved with a stiffer
spring in the slave cylinder. However, it requires that the release bearing
turn all the time. I don't know how the Toyota bearing was used in the Land
Cruiser and whether it was designed to rotate all the time.
Questions for the list:
1. How have others had this problem and if so, how have you solved it?
2. Does anyone know if the Toyota bearing is designed to rotate all the
time?
Nelson Riedel
Granville Ohio
'68TR250, '70TR6, '76TR6
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