Overdrive switch

[twospeed]

I am planning to install a overdrive in the future,can that be turned on with just a simple toggle switch----on--off style?

 

[Hillman]

In one word, yes.

BUT, it`s not that simple. You`d probably do well to consult the wiring diagrams in the tech manuals available on this site. If your OD is not attached to a transmission, you might want to search the forum for help. You may not like the answer.

If you have specific questions, revive this thread.

 

[alpine_64]

The early cars SI-II used a simple on off switch as the overdrive weas not a self cancelling type.. it also used a much more simple (and easier to find now) lucas 6RA relay. The later S3-V cars used the self latching relay and the switch had a positive return (ie a flick switch) this and the realy are harder to come by. If you used the early wiring schematic you can use a simple on/off switch.

 

[twospeed]

It looks like the S3 and later use a gearbox switch,does that just let the unit work in 4th gear?

 

[alpine_64]

It looks like the S3 and later use a gearbox switch,does that just let the unit work in 4th gear?

The S3 onwards have a switch on the box the same as a reverse light switch, what it does is self cancels the OD when it moves across the 3/4th gear plane. The OD works on both 3rd and 4th gear.

 

[Tom H]

The overdrive solenoid takes a heavy initial current to pull in, about 15 A. Most switches are not able to handle that high a current which is part of the reason that they use a relay to handle the solenoid current and a switch to energize the relay.

You can use a standard 6RA relay to operate the solenoid, and use a two posisition, center OFF momentary switch as the factory style operation to energize the relay . But you should also use the switch on the tranny to lock out the OD whenever you are not in 3 or 4 gear.

See post #9 here to see how:
http://www.sunbeamalpine.org/forum/showthread.php?t=17211

Tom

 

[twospeed]

So the overdrive solenoid needs 12V all the time it is in overdrive right?
And when the trans is out of overdrive the solenoid has no voltage to it.
I could use a 60 amp head light relay to work it with just a on-off switch?
Also,how do you shift into overdrive? Just like any other gear with the clutch or do you just lift the gas and hit the switch? Some of the trucks I drove in the 70's you would just lift the throttle hit the switch and give it gas.

 

[Tom H]

Correct, about 12 v at the solenoid and correct about the 60 A relay.
Regardiing how to switch into OD, I think most of us let off the gas very lightly when we switch it on. And I almost always turn it off simply by shifting out of 3 / 4 while using the clutch. Or I just hit the clutch briefly and turn off the OD. Every time I turn off OD while in gear I am unhappy with the lurching.

Tom

 

[Harrington Jan]

OD

Another thing, do you have a gearbox for an overdrive? I you don't, think twice.