Jim,
I beg to differ, as most automobile transmissions are not of the
constant-mesh type. Gears engage and disengage. The reason one can shift
without the clutch is that gears can be engaged without grinding by matching
the engine speed, while in neutral between gears, with road speed before
engaging the gears.
When operating a modern transmission by disengaging the clutch while
shifting their is no grinding because the synchromesh rings (concentrically
mounted with the gears) touch just prior to gear engagement and cause the
gears to rotate at the same speed before they are engaged. Therefore, we
get away without the careful shifting practiced by people in the early days
of motoring who had only non-synchromesh "crash" boxes.
Those of you who have Healeys or early E-Types may know all about
non-synchro first gears. In order to shift without grinding the
non-synchro gear, the driver typically uses the double-clutch method. First
the clutch is disengaged while the lever is pulled from whatever gear he is
in to neutral, then the clutch is engaged momentarily while the driver gets
the revs to just higher than the anticipated revs at that road speed in the
gear he is headed for. The clutch is at that stage disengaged and the gear
lever is swiftly moved home before the gear rotational speeds no longer
match due to a momentarily undriven shaft's speed dropping due to friction.
Now the clutch is finally engaged and the shift is completed. Reverse gears
virtually never feature sycnchromesh operation. In order to avoid grinding
when going into reverse gear one can still stop the gearbox rotating members
by very briefly engaging any other gear (with the clutch still in, of
course) before shifting to reverse.
When I was a kid I worked for a car dealer and drove cars all over the
Seattle area only using the clutch to begin moving from rest (funny, I never
do this with my TR6). Motorcycles typically have constant- mesh
transmissions, and yes, one can "power shift" without matching road speed to
engine speed with those. The clutch and the rest of the drive train sure
take a beating, though.
Gary
'73
----- Original Message -----
From: "Jim Swarthout" <jswarth1@tampabay.rr.com>
To: <Jsut4fun@aol.com>; <6pack@autox.team.net>
Sent: Wednesday, March 19, 2003 5:29 AM
Subject: RE: Shifting
> If this only happened once, Read "The problem WAS intermittent but
> frustrating", more than likely the friction disk was stuck to the
> flywheel. I've had this happen before.
>
> Dick, Gary
>
> The gears can't grind due to the fact that they are always meshed,
> except for reverse. Reverse is simply a floating idler gear.
>
> This is why it is possible to shift without the clutch!
>
> The noise that is heard is the synchronizers "out of sync", not the
> actual engagement of the gears.
>
> Jim Swarthout
>
>
> -----Original Message-----
> To: 6pack@autox.team.net
> Subject: Shifting
>
> I took my six out for the first time from winter storage and noticed
> that a
> couple of times while starting from a stop the shifter would not move
> out of
> neutral at all. Couldn't go into first, second, or any gear. If I
> pumped
> the clutch a couple of times it would suddenly work again. The problem
> was
> intermittent but frustrating. Anyone have a suggestion on what is going
> on?
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