Rob Munach wrote:
Brakes are for slowing the car down - even in a manual transmission
car. They are cheap and effective. You will prematurely wear out the
transmission in any car if driven in this manner.
I've seen this comment from several people on the alt.autos.audi group in
addition to here, and I have to disagree in the case of the manual: There
is no doubt that using the *clutch* to slow a car will wear the clutch, but
using the *engine* to slow the car causes no extra wear on anything, and can
actually save brake pads (though it likely uses more gas). The key, of
course, is matching revs between rotating components within the transmission
before coupling them together. This is accomplished by double-clutching to
match the lay shaft to the output shaft *before* engaging the lower gear
(reduces wear on synchros) and then matching engine RPM to the lay shaft
before releasing the clutch *after* engaging the lower gear (reduces wear on
the clutch). With a little practice, this entire evolution can be done in
about 2 seconds.
And with a little more practice, it can be performed while braking for a
corner by using the heel and toe of your right foot to operate both the
brake and accelerator pedals at the same time. (Much as I'd like to pretend
that I'm a pro at heel-and-toe braking, I have to confess that I'm still not
smooth enough with it to try it in a car that's at its limit in a corner --
I'm too herky-jerky with it to keep the car on its proper line. But I'm
getting better.) At least one person I know has a foot that's wide
enough -- and pedals spaced close enough -- to use the left and right
*sides* of his right foot to accomplish the same thing, rather than turning
his foot sidways and using his heel and toe. He's about 6 foot 14 and
drives a VW bug. I'm about 5 foot 6 and can't manage that maneuver on the
Audi (haven't yet tried on the Forester, which I've only test-driven so
far).
When driving the Olds (which has a 4-speed slushbox but is otherwise quite
sporty), I keep the car in L2 or L3 when driving through town, depending on
how fast the traffic is moving. The goal it to keep cruising revs between
about 2000 and 2500, thus giving me decent engine braking when I let off the
accelerator -- as well as good throttle response when desiring to speed back
up -- but not using that much more gas than loping along at just above idle.
If you change the selection while at a stoplight, you'll cause the
transmission zero extra wear, because it's already idling against the torque
converter in 1st gear anyway. Dropping the gear selector from D to L2 while
driving 50 mph (as an extreme example) will force the 2nd gear clutch pack
to absorb a substantial difference in revolutions -- which I've no doubt
will, with repetition, reduce the life of the transmission.
I wouldn't be surprised if some of the smarter throttle-by-wire cars that
employ slushboxes actually blip the throttle upon selecting a lower gear so
as to simulate the manual tranny rev matching described above, and thereby
reduce the resulting wear on the auto transmission. This seems especially
likely given the number of new cars being offered with "manu-matic"
transmissions (auto transmissions with a "manual" mode, like the Porsche /
Audi Tiptronic or the tranny in my Dad's old Dodge Intrepid, to name just a
few). These automakers wouldn't offer a car with a feature that is likely
to increase their warranty repair costs.
- Greg
--
1976 Cadillac Fleetwood 9-passenger sedan
(for sale:
http://www.dataspire.com/caddy)
1989 Audi 200 Turbo Quattro 5-speed sedan
2000 Oldsmobile Intrigue
2001 Chevy Astro AWD (wife's)
2004 Subaru Forester XT (turbo) 5-speed (coming soon!)
I have only had my car for ~5 months now so can't