[TR] A Type Overdrive

Randall TR3driver at ca.rr.com
Sun May 22 14:06:09 MDT 2011

>  The overdrive does not engage until  the lever is at the 12 
> o'clock position over to about the 2 o'clock position, in 
> spite of the fact that when I tested it dry the valve moved 
> up with the lever in the extreme left position.  I am not 
> sure I understand that.

The lever should have a 3/16" hole in it.  There is a matching hole in the
case such that when the holes are lined up (so you can slide the shank of a
3/16" drill bit through both holes), the valve should be in the engaged
position.  This should hold the ball off it's seat by only a small amount,
on the order of 1/32".  Sometimes the lever and/or valve rod get worn until
the holes are no longer accurate, but that is a reference point to start

The actual lever motion from disengaged to engaged is quite small, no more
than 3/16" or so.

> Now, with the motor running and the transmission in third 
> gear there is so much pressure that the solenoid is not 
> strong enough to pull up on the drivers side lever to engage 
> the overdrive.

There are several possibilities.  Assuming you have checked that the
solenoid plunger is really not moving into the solenoid, the most common is
that the pull-in contacts inside the end cap of the solenoid are dirty and
not making contact, so the pull-in coil is not activating.  Or the pull-in
coil could be bad.  (They overheat easily if the plunger doesn't bottom and
open the contacts.)  

Another possibility is that the lower stop for the plunger is missing, and
the plunger has fallen too far out of the solenoid.  Easy way to tell the
difference is to measure the current draw; the pull-in coil draws roughly 20
amps, while the holding coil only draws about one amp.

If the plunger is going all the way into the solenoid, then likely the
operating lever is slipping on the shaft.  The pinch bolt has to be really
tight to hold, due to the large force and impact it has to deal with.

-- Randall  

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