> You must be very lucky Randall or do a lot of highway driving. In
> 300,000 miles on the TR-6.
As I said, I believe the main difference is that I drive a TR3 rather than a
TR6. My daily commute is 40 or 50 miles, and most of that is in stop and go
traffic. The TR2-4 clutch is different in many details than the later TRs, and
it would appear, far more rugged. The reason there is no "magic clutch kit" or
"Gunst bearing" for the TR3 is because it's simply not needed.
One major difference is that the TR6 runs the throwout bearing all the time,
even on the highway. The TR3 design does not, the bearing runs only when
needed.
Another difference is apparently the huge variability in replacement TR6
pressure plates. Nelson Riedel measured almost a 2:1 variation in release force
... over 400 pounds for one clutch ! If the bearing can only handle a 300 pound
load ...
Yet another difference is the operating levers in the pressure plate, the TR3
uses solid cast iron levers while the TR6 uses those wimpy sheet metal things.
The TR6 also doesn't support the TOB as well as the TR3 : because of the
difference in clutch design the TR6 transmission front cover (which supports the
TOB carrier as it moves) is shorter and the carrier hangs out in space.
According to Nelson it can cock slightly and bind against the cover, which I
think might affect bearing life.
There is also the matter of the "dowel bolts", which I believe are important to
proper clutch operation. The TR3 uses plain dowels that are readily available
and hence almost always installed, while the proper TR6 "dowel bolts" are both
hard to find and commonly misunderstood. So many people, even professional LBC
mechanics, substitute common bolts (which are not the same and don't ensure
proper alignment).
Then there are the bushings that the clutch operating shaft rides in, on the TR3
the bushings are larger than the TR6 and there are grease zerks to lubricate
them every 6000 miles.
There's more, but that should be enough to illustrate the point.
Which of these differences is significant in terms of clutch and TOB lifetime, I
don't know. But I'm certainly not particularly "lucky" when it comes to
clutches ... I have a bad habit of riding the clutch when driving around town
and the clutch in my Chevy never lasted me more than about 40-50k miles. I
honestly believe the original TR3 design is simply superior, and not in need of
improvement.
YMMV of course
Randall
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