Clutch Question???

Looking over my 1991 Corolla this morning in preparation for a long
trip back home for xmas I noticed something strange. I had both of the
front wheels off the ground, the transmission was in neutral. While the
car was idling the right wheel was turning, not really fast but not
super slow either. I could stop it with my gloved hand with no problem
but it would start again when I let go. I pressed in the clutch and
looked under the car and the wheel had stopped. Let off the clutch and
the wheel started up again. The left wheel never moved. Is this a
problem and with what exactly? The car has 230,000 miles on it and
this is the original clutch. Any adjustments that need to be made or
things to check out?

In article .com>,
wrote:

> Looking over my 1991 Corolla this morning in preparation for a long
> trip back home for xmas I noticed something strange. I had both of the
> front wheels off the ground, the transmission was in neutral. While the
> car was idling the right wheel was turning, not really fast but not
> super slow either. I could stop it with my gloved hand with no problem
> but it would start again when I let go. I pressed in the clutch and
> looked under the car and the wheel had stopped. Let off the clutch and
> the wheel started up again. The left wheel never moved. Is this a
> problem and with what exactly? The car has 230,000 miles on it and
> this is the original clutch. Any adjustments that need to be made or
> things to check out?
>

Pretty much a non-issue. I haven't worked on a car with a stick that
doesn't do exactly the same thing, although the amount each vehicle does
it is variable.

With the transmission out of gear and the clutch engaged (pedal not
mashed) the input shaft of the transmission is spinning at the same
speed as the engine. On most (all?) manual transmissions, this means
that the "countershaft" is also turning anytime the clutch is engaged.
In turn, that means that the output gears, which are always meshed with
the gears on the countershaft, are also turning on their bearings on the
output shaft - at the same speeds they would be if you were in gear (any
gear) and rolling down the road - But since you've got the stick in
neutral, none of the output gears are "locked" to the output shaft. In
theory, they're free-floating. In reality, there's at least *SOME*
friction between them (at least until us stupid humans figure out a way
to negate friction completely - something I doubt will happen within any
of our lifetimes).

Since there's drag, one of two things is going to happen: The junction
between the gear, its bearing, and the output shaft is going to generate
some amount of heat when the output shaft is "locked solid" (by the
weight of the vehicle resting firmly on the ground) but no detectable
motion (unless the bearings are in hideously bad condition...) When the
output shaft is free to turn (wheels unloaded by being jacked up), it'll
move with the gear at whatever rate "downstream" friction (The total
friction of the bearings and/or rear seal of the tranny, seal on diff,
input bearing on diff, losses internal to bearings and gears in the
diff, wheel bearings, total weight of wheels/axle shaft, how much, if
any, brake activation is in effect, and current rotational speed
(inertia) of the wheels) will permit. If the amount of energy
transferred to the output shaft by the gear/bearing friction is
sufficient to overcome all of the inertia/friction that the rest of the
drivetrain puts in the equation, you've got wheel spin.

When you get right down to where the rubber meets the road, what you've
got happening isn't a whole lot different, in principle, from "slipping
the clutch" - You've got partial coupling from the input to the output,
so at least SOME rotation happens. Get worried when the wheels spin at
full speed, and you can't stop them. If that happens, you've got at
least one bad bearing between the output shaft and one or more of the
gears that ride on it. Otherwise, you're looking at normal behavior.

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See <http://www.sonic.net/~dakidd/main/contact.html> for full details.