[Larry_Horse] (Mon, 26 Jul 2004 19:36:58 GMT):

How about when your brakes are boiling..

Is your life easily replaced? ;)

How do you "gear down" (use the gears to slow the car under ordinary conditions)
when they only have an automatic gearbox?

Cheers, Peter.

that's one reason I would always prefer a manual , you approach a
corner, double clutch down into 2nd or 3rd, this synchronizes the
motor with the drivetrain. ( take it out of gear, adjust engine speed
to match drivetrain, re enguage then shift.) this puts the energy from
the braking effect into "spinning up" your engine and flywheel,
saving your brakes and not wearing your synchromesh. What you are
doing is making the gears inside the box match speeds.  then when you
come out of the corner you can then get a free boost of power as you
shift back up.   in other words you can reuse that energy, rather than
waste it.
the smooth roll in and out of gears also makes the car handle better
because the forces you are transferring to the road , braking, gearing
down, acellerating, gearing back up are one smooth motion

it takes practice to drive smoothly, more to doubleclutch smoothly
but it saves gas and your drivetrain.  I have bought cars  with
transmissions that were stubborn to shift , and worn them back into
operating smoothly,  through another 50 k of driving them smoothly.

one can take things a step further in a sporty sense,  and combine
this action with rolling off the gas and onto the brake and back on
the gas while doubleclutching down and back up. it takes practice to
get this right and the gas and brake pedals need to be situated right,
but it gives one a great feeling when it comes together into one nice
fluid motion.  

In my opinion it is the "twisting action" that wears your drivetrain.
Every time you jolt it by either accellerating or decellerating with
sudden force it makes every part involved from your pistons to the
tires on the road reverse forces with their mating parts from a
"driving" mode to a "driven" mode. this causes a wee bit of wear to
all mating parts, splines, ujoints rear axle gears transmission gears,
clutch. Even all the bearings involved are affected because the load
on them changes direction. lets not forget all the rubber parts , like
your transmission mounts etc. in lower gears you are able to stress
these parts much more than in higher gears, because more torque is
involved.
and of course the greater the force on every part , the more wear.

so my opinion for what it is worth is:
of course, use your transmission to slow you , but the harder  you
"jolt" your drivetrain, and the quicker it will wear, so if  it goes
down into a lower gear with a great  big thud it probably isn't a good
thing. same goes for  flooring it in first.

also since it is a proven fact that if one chooses roads which go
downhill, one will save gas. so if you have a choice , go downhill in
mexiican overdrive (neutral)    :)

Phil

Unlikely to say the least.  Nowhere that dramatic.

Okay.  My fault.  I didn't adequately describe my thoughts.

I'm not afraid I'll burn up my brakes in long one panic stop while
descending one of our hills around here.  They are HILLS (steep ones, yes,
but hills nonetheless) not mountains - and I'm driving a CAR, not a
commercial truck with an 80,000 pound GCW pulling me down a long mountainous
decline at ever increasing speeds while I desperately scan the road ahead
for an emergency off ramp.

None of that applies.

What DOES apply is that in this neighborhood I burn up a set of front brakes
every 4 or 5 months.  Every third reline I replace the front rotors too and
they're about $120.00 each and of course now and then I've also got to do
the rears --- so my brake maintenance costs over time are quite a bit higher
than somebody who just toodles around on flat ground.  Right?

That's issue number one.

Issue number two is that I try to take some of the braking load off my wheel
brakes by pulling my automatic gear selector into 3 or even 2 while
descending these steep local grades.

Which leads to my QUESTION:!:  "Am I wise to continually use my engine's
compression braking effect to slow the car and extend brake life over a
period of time - or will this inevitably result in early and
catastrophically expensive transmission failure and ultimately COST me more
in the long run than I'm trying to save in the short run?"

That's all.  That's the whole question.  Pretty straightforward.

I have no interest in debating whether or not a manual is better than an
automatic or any of that stuff...not that I had any choice in the matter
because a US-spec'd 2001 S80 with a naturally-aspirated 2.9L engine only
comes with ONE transmission 'choice' and it happens to be an automatic.  So
it is what it is.  If ya like the whole car ya buy it automatic and all, and
I did.

Pat