Let's see - you're looking at the Bentley Manual, either page 167 or - more
likely from your description of the diagram - page 313. This is a separate
harness, you could make it yourself, or buy it from a major MG parts house -
moss
number 357-388 (if it is still available), victoria british I can't tell for
sure, but looks like part 8-7501, - can't seem to find the OEM # right now. It
will be easier to buy than to make.
Question 2 the answer is probably no. If you buy the harness from a breaker,
you
may get this stuff, if not, you will have to buy it. Everything is available
except the "throttle switch," which is a.k.a. a "vacuum switch." They can be
had, but cost plenty - I searched for a year and paid $120. The beauty of the
situation is that you don't need it, and it wasn't even installed on most cars,
so you can ignore the throttle switch. Even if you get it, you need to tap the
intake manifold for vacuum, and the fittings are not readily available (I never
did find them, just bought one a newer style replacement from Swagelock through
my place of work at the time). The rest is easily buy-able. You will probably
want to know the location for them. The relay goes against the firewall on the
driver's side (there should be two philips head screws there just for that
relay), and if you get one the vacuum switch goes below that, in approx the same
location. If you don't get the vacuum switch, just don't connect the two wires,
they should remain unconnected - I could write a dissertation on how the vacuum
circuit works, but it really isn't worth it right now. Part 73 is a lockout so
that you can not use overdrive in R, 1, or 2. It will be part of the OD
transmission. If there are two similar switches, congratualtions, you have a
very rare OD trans with a back-up light switch - I'd love to trade you, I have
the back-up lights on my '67 MGB, but no switch on my O/D trans.
The overdrive unit is pretty robust. It is fairly common to get the solenoid
out
of adjustment. Also be careful where you run the solenoid wire (it can rub and
short out - had it happen, had to fix it). The speedo cable is different than
non-OD, and will go in odd place, for example, the starter is likely to rub it,
and wear it out, so "fix" it to something to avoid this. Officially the drive
shaft is a different length too. You will want to check your car, and make sure
that with the body suspended (not by the suspension) and all of the suspension
travel out, that the driveshaft you use is long enough to stay connected, and
not
break bolts on either end.
Good luck, If you want to know how the trottle switch functions, let me know -
it
is not how most people think it should function - or you can read up on it in
the
Bentley manual on page 167, but it won't really make sense until you experience
it.
Phil Bates
67 MGB with overdrive
Misc. others
Mgbbob@aol.com wrote:
> Hi there Listers,
> I've been away from the list for a while and it's a real pleasure to get back
> in.
>
> I have a few questions that I'd like the list to comment on.
>
> I just acquired an overdrive for my 1966 B (GNH3L78708) with a GB series
> engine.
>
> 1. Bentley's wiring schematic (diagram 2) shows items 68, 71, 72, 73 and
> 74 as part of what seems like a separate harness. It's shown in
> phantom so I assume that this is not available unless the
> overdrive is ordered. Is this true?
> Will I have to make my own harness?
>
> 2. I've been told that the OD relay unit (68), the gear switch (73), and
> the throttle switch (74) are all included in the main harness. Is this
> true? Are they available?
>
> 3. Are there any other problems I'm likely to encounter in this
> conversion?
>
> Thanks in advance for your comments listers..........I really need to resolve
> these issues.
>
> Bob Stahlbush
>
> 66 MGB RD GHN3L 78708
> 60 TR-3A TS 81398 L
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