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RE: Overdrive Wiring Questions

Subject: RE: Overdrive Wiring Questions
From: John Bartholomew <>
Date: Tue, 4 Jun 96 08:11 PDT
'70 GT
'68 roadster
(sniff..this space for rent): Wrote

>Subject: Overdrive Wiring Questions

>Need to reconstruct the wiring harness for the overdrive unit. This >is new
territory for me, so I could use some guidance/wisdom.

>There appear to be three points for electric connection. One is a
>dual-pole switch on the left of the tranny, there's a similar one to >the
right, and a single-pole connector on the right hand side of the >gear tower.

>Realizing the yellow wire in the bundle at the firewall is the power >for
the circuit - what constitutes the harness. From the GT I parted >out this
past winter, I was able to salvage the remnants of what I >believe was this
harness. That old GT was originally equipped with >OD, but whomever removed
the engine, chose to chop this harness. >What's left are two green wires,
and a yellow/red.

 The two green wires are the reverse light switch connections, the
yellow/red is the wire that connects from the yellow "bullet" that you
identified as the power source, to the 3rd/4th engaged switch.

>Where on the unit is the solenoid?
 It is inside the large appendage on the rear of the tranny. You should see
a wire go into the lower side of this "appendage".

>Can anyone provide a) advice, b)a diagram,c) a complete OD harness,
>firewall to tranny?

>All and any assistance would be appreciated.

     As you have correctly identified, the power feed to the OD is the
yellow wire. This should be "hot" when the OD switch (wiper control) is
pulled up toward the steering wheel. There should be no voltage present when
the control is pushed away from the steering wheel.
The yellow feed then goes to the switch on the left of the tranny, looking
from the output flange. This is the 3/4th gear engaged switch, prevents use
of OD when in first/second/reverse. From the switch go straight to the OD
solenoid. The other switch on the tranny is the REVERSE light switch.  Hope
this helps. - John.
John D. Bartholomew  Amdahl San Jose CA.  Usual disclaimers apply.
     408-746-6361 - Voice Mail            408-746-8016 - FAX
               Internet id -
 69 MGBGT; 74 MGB; 76 MGB Restored; 72 MGB daily driver; 79B For Sale;

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