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MG MGB Technical - Move overdrive switch to gearlever - V8

Picking up on the V8 expertise that is obviously here...

I would like to move the overdrive which is currently on a stalk next to the steering wheel on our V8 onto the gearlever using one of the B&G period gearlever switches.

Ideally I would like to tap into the existing overdrive circuit ( yellow?) inside the cabin and in a perfect work not to have to cut any cables. The current switch is via a multiblock connector, unlike a B which is dead easy to get at with a couple of cables into the back of the dash mounted switch.

Any hints on where to access the overdrive cable?
Mike Dixon

For me the column stalk was the best version as I could flick OD in and out with a finger tip and hands on the wheel, and anticipated the much-vaunted paddle change. Sadly now replaced with a 5-speed conversion.

Where the yellow (maybe yellow/red) in the gearbox sub-harness joins the yellow in the main harness in the engine compartment simply move the OD wire into the spare position in the 4-way bullet connector with three white wires already there, that's how the 77 and later 4-cylinder cars were done.

Then insert the gear-lever switch between the gearbox harness wire and the tail from the solenoid. But as with the fuel pump in another thread insert a fuse between the OD wire and the whites as the gear-lever wiring has been known to short out. The attached from a pal's car didn't actually short out (unlike his fuel pump wire, see other thread), but can't have been far from it.



paulh4

Tend to agree with Paul-I like the old dash mounted flick switch specially with one of the rubber rally switch extensions--real easy to flick with a finger without letting go of the rudder, just a matter of perfecting your timing while changing gears----would be the same with a stalk , weirdly i think i've only ever driven one car with the stalk switch, it was ok from memory.
If the fella in your head really wants a gearknob type switch make sure you've got plenty of length in your wiring and where it runs down the gearlever do a couple of really loose laps around the bottom of the lever base before heading off to the loom--that'll stop the wiring getting pushed and pulled about every time you change gears.
Ahh yes, and by the way, have a real good look at the steering rack mounting pedestals where they weld onto the front crossmember, they're a bit prone to cracking there on v8's that have been driven with a little enthusiasm.

willy
William Revit

Incidentally I can't find a B&G gearlever switch but if it's an after-market conversion with a long tail rather than the factory one which only goes to the bottom of the gearlever then that would be connected in the same place as above i.e. between the gearbox harness OD wire and the white wires, leaving the solenoid wire as it is.

In either case you can then use the OD stalk switch as a cut-off for fuel pump or coil.
paulh4

I fitted a gear knob O/D switch on a Triumph Dolomite I had - basically the same parts as was used on the MGB. Quite honestly the switch was of poor construction and it kept popping off the top of the knob. I worried about the longevity of the switch so fitted a relay to lighten the electrical load on the crappy contacts. Then of course there are all the tales about the wires chaffing at the bottom of the gear lever. Personally I wouldn't bother.
Mike Howlett

Yes, the factory switch _is_ flimsy and a fiddle to fit. With a new cap I had to wrap slivers of insulating tape round the body of the knob in three layers before it would stay in place. It does only handle 1 amp though, unlike the 3-synch D-type which takes 17 amps initially and 2 amps once engaged which is one of the reasons that system used a relay, even though the dash switch is more robust.
paulh4

It is part number STN1052 on B&G, it took me a while to find it, image of a similar one below.

I have one fitted to our B and find it really intuitive to use and where I expect the gearchange to be - you can take it out of overdrive and switch down a gear all at the same time if required.

Easy to feel the state of the O/D without looking




Mike Dixon

Wires not long on that either needing to access the solenoid wire beside the gearbox or extending them so they reach the bullets in the engine bay. Going by mine the gearbox wire won't go down far enough to be accessed from below easily nor the solenoid wire long enough to be accessed from above through the tunnel hole at all.

The Dennis Welch type looks to have longer wires but single insulated. I would run those inside the tunnel with the gearbox harness rather than through the cabin and into the engine compartment through the bulkhead, but sleeve them first i.e. heat-shrink for protection from chafing.
paulh4

I like that switch much better than the top of the gear knob type. Providing you take care with the wires as Paul says, it really looks the part. Isn't that what the works cars had?
Mike Howlett

Went for a Club drive this morning. One car was a pretty Austin Healey 3000. I noticed that the overdrive switch was built into the gearshift knob. The switch was halfway down the cylindrical knob and faced forward. I've perused moss and can't find this setup. I'm an MG guy so I don't know if the knob is an AH part or cobbled from some other marque. I think early Jags had the same or a similar setup.

Jud
J K Chapin

Hey Jud
Dennis Welch sells them with a nice amount of wiring attached.

https://www.bighealey.co.uk/gearknob-overdrive-switch-cels123
William Revit

Yes, that's exactly what it looks like. Thanks.
J K Chapin

This thread was discussed between 11/03/2025 and 13/03/2025

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