Stu Bollen writes:
>Today I tried to reverse with the O/D engaged. Luckily it does not seem
>to have done any damage. (J type).Is there supposed to be any kind of
>electrical lockout when reverse is engaged? I never did this before,
>wondering if a wire has come off somewhere.
>Stu
>74 Tr6 80 TR8
Stu,
Yes there is supposed to be a switch mounted to the transmission cover
which will prevent actuation of the overdrive in any gear other than 3rd
or 4th. If that switch is not there, or is bypassed, or is malfunctioning,
and the overdrive is engageable in any gear you run the risk of reversing
with the overdrive engaged.
The J-type overdrive has no pressure accumulator and the pressure used
to actuate the O/D clutches is derived directly from the pump. If you
are starting from a standstill (no movement for several seconds) there
will be no residual oil pressure and the clutch will not be actuated
even though the solenoid is. Depending on how far and fast you reverse
(notice the British idiom "reverse" as opposed to the American equivilent
"back up", a result of my recent visit which I enjoyed immensely!) the
clutch
might never engage the overdrive and thusly no damage will occure.
In the event that you do reverse sufficiently far and fast to cause the
clutch to begin to engage the O/D the initial effect will be the sense
that the brakes are being applied and if very little throttle is used
the engine will stall before damage is done. This has been my experience
when the one-way clutch was installed (by us :-0) the wrong way round.
The engine stalled when the O/D was engaged in any forward gear but when
the O/D was engaged with the transmission in reverse every thing worked
fine! Weeelllll, time to take it back apart and start over! ;-(
I guess the moral is that engaging the overdrive and backing up (reversing)
is not a recipe for instant disaster, but don't do it again.
As far as a fix goes, If the transmission does not have a lockout switch
and it is inconvenient to get a tapped hole machined for it, one could
wire a relay to the reversing lamps (back-up lights) and wire up the
solenoid through the NC contacts thus disabling the OD when reversing.
Good luck
Dave (I'm back from my much too short visit over there) Massey
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