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A type overdrive isolator switches.

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Yes, if the stalk is still in the on position the OD will re-engage on entering the new gear. This situation can be avoided if you buy an OD Logic Controller.

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Hi Malcolm,

welcome to the forum.

The OD is quite a simple device and once the operating is understood it is a great addition to the car.

As mentioned above with the control lever in the on position the OD drops out between changes but will re-engage when in a suitable gear.

Remember to dis engage OD between gear changes.

When you do engage OD ensure that the revs are slightly raised. This will allow a smooth engagement. If you allow the revs to drop the engagement will be quite rough.

Some users depress the clutch but this is cheating.



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Hi Malcolm,  Welcome to the world of overdrives!   You don't actually have to turn the overdrive off if changing  gear up or down for as Ian says, the overdrive will automatically disengage and engage again when in the new gear.  Its does this because the electrical circuit is momentarily broken when changing gear.  If your overdrive doesn't disengage when changing gear then you have a problem which needs sorting.   As its quite possible to forget that you are in overdrive when you come to a stop the overdrive will automatically disengage when you select first gear but it will engage o/d 2nd when you change from 1st to 2nd gear ( assuming you have o/d 2nd) . On a later TR6 then it will engage o/d 3rd when you change up from 2nd gear. 

Hope this helps. 


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Funny how you learn something everyday.

Had the car since 1998. Done some fairly major restoration work over the years. But for some reason have always thought that the overdrive (when selected ) remained engaged when shifting up or down 2-3-4. Not that it disengaged and then re-engaged at each shift.

Next thing is some ones going to tell me the earth is round.

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No it's not !!!   It is an oblate spheroid.

29 minutes ago, RogerH said:

No it's not !!! :o  It is an oblate spheroid. 

And that is why the OD disengages between gear changes.



Sounds like something you would not want to catch. Or medication you would take to cure it.

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59 minutes ago, Malcolm Clarke said:

No the overdrive OD its self does not drop out. I was just surprised that the solenoid via the iso switches does.

The way they're set up - on/off switching from the gear selectors they have no other option. These days a transmission control computer would be programmed to hold the solenoid in for as long as O/D was selected.

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