Date: Thu, 30 Mar 2006 23:56:44 -0500
To: WSFA members <WSFAlist at KeithLynch.net>,
    WSFA members <WSFAlist at KeithLynch.net>
From: "Mike B." <omni at omniphile.com>
Subject: [WSFA] Re: Metro is 30
Reply-To: WSFA members <WSFAlist at KeithLynch.net>

At 3/30/2006 06:28 PM, Ted White wrote:

>Instead, a sensor is located in the transmission
>and it sends signals by wire to the dashboard unit.

Yep.  In at least some cases the sensor is just a magnetic pickup
positioned over a gear, and as each tooth passes the sensor, there's a
change in the signal it sends.  The "gear" may or may not have
equally-spaced teeth, and may just be a special wheel or paddle, not
anything resembling a real gear.

>As an electrical
>circuit, it is more prone to failure -- which can occur at any point
>between the dashboard and the transmission, but usually happens *in* the
>transmission, which is a very expensive job to fix (involving as it does
>removing the engine in order to remove the transmission, in order to
>open it up).

Depends on the vehicle...in my Harley it's pretty easy to fix the sensor,
and no engine removal is needed.  You just unscrew the connector and the
sensor comes out.  Often the only problem is that it's got metal shavings
from the transmission gears on it, and wiping it off and reinserting it
will fix the problem.  From what I've heard, this happens most often in the
first few thousand miles as the gears are wearing to fit each other
better.  It didn't happen to mine, but I have seen a bike with this
problem.  The speedometer was reading slow, and the mileage was reading
lower than it should after a ride.

Some cars have the sensor equally accessible, once the car is on a
lift.  You'd only have to pull and open the transmission if something went
wrong with the gear...such as it slipping on its shaft, losing teeth or
whatever.

>Imagine the possibilities.

Yep.  "What do you want your odometer to read today?"  Harley dealers have
a device for calibrating the speedometer already.  I expect that car
dealers have something similar for cars that have this sort of system.

I can see ways they could make this much harder though.

-- Mike B.
--
Those who can, do.  Those who can't, simulate.