Rich,
You are a fortunate fellow!
Yes, to engage the OD, pull the lever toward your chest. Use it in 3rd
or 4th, depending on how it's wired into the gearbox. Your revs should be
at least 2800 in N (N is Normal, vs OD for Overdrive) so that the revs
don't drop too low when the OD engages. You will feel it shift and see
the tach drop. The pump in the OD is driven by the output end of the
gearbox, so it won't pump up enough pressure to work at road speeds much
below 30 mph. It's easy, though, to forget to switch back to N at a
stoplight, then to feel the OD engage disconcertingly at 25-30 mph as you
are driving out of the light.
If the previous owner didn't tell you that the car had OD, it may not
have worked for him. First thing to check, then, if it does not work, is
that with the shifter in 4th and ignition on, that you get 12v at the end
of the yellow wire where it connects to the skinny black wire just at
the bottom of hte unit. That is the connection for the solenoid. It is
said that you can hear the solenoid click when the engine is off and you
flip the switch. Maybe in the type D ODs, but I have never heard it in my
LH, which is the type you would have also. If you don't have power at
that wire during this test, then work backwards from solenoid to the 3/4
gear switch, buried on the transmission just forward on the left and out
of reach from the gear shift rubber glove. Look in there and be sure that
there are two wires on that switch. Test that there is power to that
switch when the selector lever is set for OD. If no power in, then keep
working backwards toward the selector lever. You really need the WS
manual at this point.
Now, assuming that you did have power to the solenoid but that the unit
doesn't work, you may have an easily solved problem. First thing to do is
to drop off the filter and the covers and replace all the little o rings.
They work under a lot (400 + psi) of pressure, and they do get hard with
age. While you are replacing them ($20) check that the orientation of the
pump piston is correct. If it's 180 degrees out, it will push down once
and bind in the bore of the pump. Look carefully at it--the roller
carriers are not quite identical, and that's how one determines the
different sides. While you have the bottom open is the time to ground
the solenoid and test that it does snap its piston in and out. Careful
when removing it as you don't want to pull on the wire and pull it off
the solenoid. The connection is just a little bit of solder.
When all the rubber bits are refreshed and the solenoid is known to be
working, fill up the gearbox with 20/50 and take her for a test drive.
Keep us posted on the exciting developments.
Bob
On Sat, 16 Jan 1999 13:14:23 -0600 richard.arnold@juno.com (Richard D
Arnold) writes:
>List:
>
>If I may demonstrate my ignorance for a moment (you'll get used to it,
>I did). I finally took the time to look under Miss Maggie )the 74.5
>RB MGB, and discovered that she is equipped with an overdrive unit. I
>remind you that I've owned her for several months, but haven't driven
>her and performed damned little work on her, thus I didn't know until
>now that the OD was there.
>
>Needless to say, I am quite tickled.
>
>I assume that the switch is on the wiper control (pulls toward the
>driver?). Can anyone explain these puppies to me? I know less than
>nothing about the OD's. Problems, concerns, maintenance, how do I
>know if it works, etc, etc, etc.
>
>Rich (who really has to spend more time under cars!)
>Council Bluffs, Iowa, USA
>
>'74.5 RB MGB "Miss Maggie"
>'78 Chevy Half-Ton "Waltzin' Matilda" (LBC Support Vehicle)
>'79 Midget "Miss Molly"
>
>richard.arnold@juno.com or rdarnold@neonramp.com
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