Bill Kelly wrote (and Randall Young agreed) that:
> >Actually, experience and theory both indicate that a worn clutch will
> >begin slipping in top gear, working its way down to lower gears
Then Dave Massey replied:
> I think your both goofy!
Sorry Dave, but they aren't goofy! A decade ago when I went through my
slipping clutch woes, I did the analysis that BK and RY did and I came to
the same conclusions. My experience was exactly as they described, slipping
in higher gears, especially 4th with OD engaged or going up hills. In fact,
I was trying to find a reason why that would happen, rather than starting
with the analysis and looking for the behavior it predicted. Had I done it
the other way around I might have "found what I was looking for" instead of
what was actually happening. (Of course, one can argue that my analysis was
skewed by my trying to explain what I had found. Yes, I did conclude that I
was *not* observing the OD slip.)
One possibility is that one notices clutch slippage more readily in a higher
gear. The reasoning is this: If you depress the accelerator more than a
steady-speed throttle position, a low gear will let the car accelerate
easily. Even if slippage happens, you can't see it because both the tach
and speedo are moving upward together. Perhaps they aren't moving quite in
accord with each other, but the difference in their rates can't be judged
easily without a precise numeric comparison. In conrast, depressing the
accelerator while in a higher gear, especially on a hill, may result in
little or no acceleration at all. Tach movement accompanied by no
corresponding speedo movement is all too obvious!
Thus both dynamics analysis as per BK and observational precision suggest
that slippage is indeed observed first in higher gears. But I still
wondered which was the real explanation, observational error or dynamics.
So I endeavored mightily to observe slippage in the lower gears. After much
watching and accelerating and the going up of hills in lower gears for that
purpose, admittedly all without the aid of speed-recording devices, I was
never able to satisfy myself that had actually seen it. Since I also trust
the physics, I'll put money on the dynamics explanation. Not only will you
observe it first in higher gears, but it is also likely to happen there
first!
Jes' my two pence.
--
Jim Muller
jimmuller@pop.rcn.com
'80 Spitfire, '70 GT6+
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