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MG MGB Technical - 3 Synchro overdrive vacuum switch

My son and I are about to embark on replacing the 3 sync, non-overdrive gearbox in his '66 Mk1 BGT with a 3 sync overdrive type. We have successfully completed this job before on previous cars, so without too much concern we set about sourcing the parts required. The passage of time has clearly had an effect on parts availability because unlike in the past, locating the requisite vacuum switch BHA4282 which is used on 3 sync boxes (the one fixed to the bulkhead with a pipe to the inlet manifold), is proving something akin to the search for the proverbial hens teeth. Although much has been written about the question of the necessity of actually having the switch (there is some excellent info in the archives), apart from the originality standpoint, I am one of the school that believes that running without one is tempting fate and would probably lead to damage to the OD unit during any period of 'energetic' driving. I feel sure someone somewhere must have one of these switches tucked away and gathering dust at the back of their garage. Any help gratefully received.

Chris
Chris Woodfield

They do appear to be quite rare and command quite a price when they do turn up.
Dave O'Neill2

Chris
What price are you willing to pay for one as i have one in the garage that im keeping for a rainy day.

Thanks ste
Ste Brown

Can't help with finding one, but I did an article on taking the unit apart and rebuilding it.

https://sites.google.com/site/cunhab52/mgbvacuumswitchforod
Bruce Cunha

Chris - E-mail me at SUfuelpumps@donobi.net, I may have a lead on the switch (and the companion relay) for you. Cheers - Dave
David DuBois

Ste,

Thanks for your prompt reply. If you email me with your phone number I will call you and we can discuss.

woodfield88@googlemail.com

Thanks,

Chris
Chris Woodfield

Bruce,

Thanks for the link. We have just had a read of your article. It is superb... and may prove very useful in future!

Thanks,

Chris

Chris Woodfield

Bruce,

Brilliant article! I am going through everything I can think of to get my MGB "right" and I got the parts in the autumn so this will help when I get around to the job. Not quickly though: it will be after replacing the water pump and a few other cosmetic jobs like bonnet soundproofing, and hopefully after getting the original engine back in the car.

John.
John Prewer

I wouldn't get too worried about that switch. I never bother running them and nothing dire transpires as a result.
Bill Spohn

The fun that switch adds would make it worth doing. It urns the car intoa semi automatic, almost.
Stan Best

Good news... Ste came up trumps with a nice example. Thanks to him and everyone for their comments.
Chris
Chris Woodfield

This thread was discussed between 01/05/2013 and 12/05/2013

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