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Re: Overdrive on 77 MGB

To: Robert Williford <RDWILLI@VM.SC.EDU>
Subject: Re: Overdrive on 77 MGB
From: Tom McLaughlin <tomm@ti.com>
Date: Wed, 01 Oct 1997 16:20:46 -0500
At 05:03 PM 10/1/97 EDT, Robert Williford wrote:
>what do you mean by bypassing the lockout switch?  how does one do this?
>i ask because i think this switch is bad on my od unit.
>any help is appreciated...
>
>-robert
> 73 b w/ 80 od
>
>
The switch on top of the gearbox on the left side only allows the overdrive
to engage when you are in 4th (or 3rd on some models).  I believe when you
are in 4th, the switch is closed, mechanically.  I had a problem with the
OD falling out when I stepped on the gas.  It was suggested that the stick
was being torqued away from the switch. (Not really sure how this works)  

There are 2 leads to the switch.  I just pulled them off and jumped the
wires together.  The caution is not to allow the OD to engage in any other
gear but 4th, especially not in reverse.

Below is the message that helped me the most....thanks Scott.

=========

There are two switches that control power to the OD.
One on the dash, and one in the gearbox.  The dash switch lets YOU switch
into OD;
the gearbox switch only lets the OD on in the proper gears.  They must both
be closed
for the OD to engage (column switch on, AND car in 4th gear). 

The gearbox switch is located on the top of the gearbox, on the left
(drivers) side.
 It is a round doodad that screws into the top of the remote shifter
housing.  There
is a fibre washer under the switch. 

Again, the function of this switch is to tell the O/D when the car is in
4th gear
(or 3rd and 4th with early gearboxes).  As you shift into 4th, the switch
closes
and power can flow to the solenoid (assuming the dash switch is closed
also)  If
YOU try to engage OD in any other gear, this switch will interrupt power
and the
OD will not kick in.

Over time the brass tip of the switch wears away and as a result isnt long
enough
to mesh with the cam in the gearbox remote.  As you drive, it bumps around-
in and
out and causes this symptom.  To test the switch, make sure the column
switch is
OFF and then yank off the two wires to the switch on the gearbox and
temporarily
jump them together with a test lead (tape them up with electrical tape).
This effectively
defeats the gear lockout so DO NOT ENGAGE THE OD SWITCH ON THE DASH IN ANY
GEAR OTHER
THAN FOURTH, ESPECIALLY REVERSE!! (too much torque in the lower gears or
backing
up can trash the OD clutch.)

Get the car up to speed and into 4th gear.  Switch the OD on and see what
happens.
 If the OD still drops in and out, you have eliminated this switch from the
list
of culprits.

Happy hunting!



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