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O/D trans installation. Couple of thoughts?

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Bret

Bret

Yoda
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In relation to my Speedo question in another thread.

I'm getting ready to install my O/D transmission but I have a few questions about how the overdrive solenoid is engages with the shifter switch.

I’ve got the shifter knob with the switch ready to go but looking at the Moss & VB catalog and perhaps I missed it but I couldn’t find the any reference of the O/D vs. the none O/D transmission wiring harness that I need.

Anybody is this something I can mock up on my own or do I need to have the wiring harness. I assume I can just pick up the 12v to actuate the O/D solenoid using the “fourth gear” wire that connects to the 4th gear vacuum advance solenoid. So I’m guessing that if the None O/D & O/D main wiring harness are identical – there should be a connector under the trans tunnel that I can connect to.

Any thoughts?
 
I think the OD harness probably also makes allowances for the 1-2-R gear lockouts too. You should be able to make your own, but at least set it up to disengage when in reverse.
 
I know early B's allowed operation of the O/D in both 3rd & 4th. but Later B's with O/D transmissions like my 78 only engaged the O/D in fourth.

I'd have to look at the schematic to be 100% sure, but I believe that the fourth gear enable sensor for the Dizzy's vacuum advance, should lock out the over drive from every thing including reverse and only allow engagement of the Overdrive in 4th.

Guess I'm just wondering if there’s a connector down there for the O/D cars, that’s *unused* in the existing harness that I can attach to without any cutting & splicing into 30 some odd year old wiring. Other than that I’ll have to run a bunch of extra wiring on my own. Just hoping to make use of anything that might already be in place.
 
Bret-

No special harness is needed. Wire the solenoid in series backward as follows (according to John Twist's Technical Book):

From the solenoid to gear stick switch to lockout switch (switch only closes in 4th on yours, earlier gearboxes closed on 3/4) to impact/rollover switch to any white wire of ignition.

If I were fabbing a harness from scratch, I'd also add a 17amp fuse in series just off the ignition feed, as this circuit is unfused and a dead short will cause lots and lots of smoke to escape :smile:
 
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