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Re: Overdrive Swap

To: MG List <>
Subject: Re: Overdrive Swap
From: Max Heim <>
Date: Tue, 05 Jun 2001 10:41:00 -0700
Hmmm, I don't know how you could wire it to tell that it is really engaged.
You flip the OD switch (assuming you're in 3rd or 4th gear so that the
lockout switch is closed) and it sends juice to the solenoid, which
activates the OD (hopefully), or not (if it's defective) -- either way,
you've powered the circuit and the indicator light goes on. (Mine is
actually wired so it glows if the OD switch is on, regardless of the status
of the lockout switch -- this is probably the preferred way because it warns
you if the switch has been flipped accidentally any time the ignition is
on). You would have to install a pressure-activated switch into the OD case
to see if the hydraulic pressure is up, or a rotational speed sensor on the
shaft, or something complex like that, tied into your indicator light. But
why bother -- it's totally obvious if the OD is engaged -- the revs drop by
something like 800rpm. If it doesn't engage when you flip the switch in the
appropriate gear, then you can start looking for the problem. First check
for juice at the solenoid. If you're not getting any, check the lockout
switch for proper operation (easier said than done, on the car, except on
Mk. Is), and the entire circuit for continuity. If it's getting power but
not operating, it may just be stuck. I'm pretty sure you can remove the
solenoid from beneath the car for an inspection. Hope this helps.

on 6/5/01 9:45 AM, Andrew B. Lundgren at wrote:

> So did you wire it to tell you when the overdrive is really engaged, or just
> when the switch is flipped.  I have some converns about my solenoid being
> defective and would like to monitor it closely...
> On Tue, 5 Jun 2001, Jack Feldman wrote:
>> No one seems to have mentioned that it is a great help to wire an indicator
>> light to let you know when the overdrive is engaged.
>> I find it easy to hit the switch when reaching behind it. The light lets me
>> know that I have gone out of overdrive. I usually am to interested in
>> steering to constantly watch the revs.


Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.

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