I did the O/D swap back in '98 but the other way around (79 'box onto my
74). Bolted right on the engine and into the car. The original driveshaft
works as well.
Couldn't figure out the wiring until I realized the late 'boxes had the
switch on the shifter and all earlier cars were wired for the o/drive
regardless of actual installation. I only have o/drive in 4th (as Paul
stated, seems to be a late model item anyway) but I only have one wire
running from the solenoid to the harness up near the firewall. Seems to work
fine.
Are you sure? It was so for the column switch but a 79 would have had a
gear-knob switch, the Parts Catalogue shows a different gear-knob cap for
non-OD cars. The main part of the harness will be present on a non-OD 79
for the TCSA system and that includes the gearbox lockout switch that
operates in 4th gear only. There should be a yellow wire from the gearbox
switch to a 4-way bullet connector and a yellow/back from there to the TCSA
solenoid. You will need to add a wire from this connector to the gear-knob
switch and from that switch to the solenoid. This is different to how the
73 was wired. If you don't have or fit the gear-knob switch and have a
manual switch elsewhere e.g. on the dash you will have to be careful how
you
wire it. You *must* keep the gearbox lockout switch in circuit or you can
destroy the OD, and if you interrupt the wire *to* the lockout switch you
will also be switching the TCSA, which may cause strange effects to the
engine as you switch OD in and out and give you poor mileage in non-OD.
My info also shows a 1280 TPM speedo not a 1290, FWIW. Whatever, with a 73
gearbox the existing speedo will be miles out! But are they rare? I
thought all North American cars from Nov 67 to Sep 74 (end of CB
production)
had small 1280 TPM speedos.
PaulH.
----- Original Message -----
From: "Larry list account" <list@marketvalue.net>
To: <mgb-v8@autox.team.net>
Sent: Monday, January 19, 2004 3:18 PM
Subject: Swapping to an OD transmission.
> > i have a transmission w/ overdrive from a 73B. would like to
> > install in my 79B. other than swithching the drive shaft, are
> > they interchangeable?
>
> You may need to build or source the wiring harness (three wires) you
already
> have the OD switch in your car.
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