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MG MGB Technical - Laycock overdrive

A friend mentioned to me that years ago when he had his MGB people would sometimes put a Laycock overdrive unit on the transmission when the car came from the factory without overdrive.

I've done a little Google searching but haven't come up with much. Was this modification a good idea? Is it something that can/should be done today?

Thanks,
BH
BH Davis

Congrats on the fourth...

The Laycock (de Normanville)overdrive is the od that comes with the MGB originally. Itīs a common upgrade to buy a complete gearbox with the od attached.

Call on any major MG parts dealer in the US.

Erik
Erik

Or better still just have a look at this http://www.octarine-services.co.uk/#kits
Iain MacKintosh

That's pretty neat - I didn't know such conversion kits were available. But on the high side, pricewise, for those of us in the colonies. Over the years I've found two parts cars with overdrives: one for $325 and the other for just $200. In both cases, I was able to sell enough parts off the cars to pay for themselves, resulting in two free overdrive transmissions. My only remaining cost was that of rebuilding them.

Other options are conversion to 5-speed transmissions:
1. the Ford Sierra kit from Hi Gear iin the UK, or
2. the Rivergate/Datsun kit available in the US.

FWIW,
Allen
Allen Bachelder

The conversion to a five speed is in my opinion a retrograde step. Overdrive provides essentially a six speed setup but moreover provides the facility where on winding roads 3rd can be selected ond overdrive flicked in and out at will give a wonderfully flexible system that could not be achieved with a five speed. In addition the overall charm of these cars would be completely spoiled by the inclusion of a modern five speed box.
Iain MacKintosh

Same here. Not only is 3rd OD a very useful intermediate gear for twisty bits and certain grades of incline, it is so much easier to flick OD out for overtaking and back in again afterwards than changing gear. My Celica 5-speed doesn't have the torque of the roadster in 4th OD to give any decent kind of acceleration, even though on paper it is as least as powerful as the V8. Having to use clutch and gear lever to change down, and back up again, half the time I can't be bothered, which is why it is such a boring drive.

I say 'is', but yesterday I got a long searched-for ZS 180 and have moved the Celica on. I'm now the proud owner of 18 cylinders of MG!
Paul Hunt 2

I installed the Hi-Gear 5-speed conversion on my 73 MGB and was delighted with the results. I went this route instead of sourcing an unknown used OD.

My current car is a 75 TR6 and it has OD fitted. I agree with Iain that it is a preasure to use third gear on the twisty roads or in town and flip OD on and off as reqd.

Barry
BJ Quartermaine

I installed the Hi-Gear 5-speed conversion on my 73 MGB and was delighted with the results. I went this route instead of sourcing an unknown used OD.

My current car is a 75 TR6 and it has OD fitted. I agree with Iain that it is a pleasure to use third gear on the twisty roads or in town and flip OD in/out as reqd.

Barry
BJ Quartermaine

In very simple terms please.
How can i get overdrive on secondgear on MGB GT. Can it be done.
David Angel

David,

The simple truth is very well covered in the archives and here.

1. Straight wire from power to the solenoid. Gives you OD in all gears.

2. As stated, wiring a relay via the reverse switch is a great idea. Takes you out of OD and no damage.
Leaves OD in all other gears.

3. I converted my 72B to OD from a 76B, makes for a great ride, and I left wiring same as factory. OD only in 3rd and 4th gear. B doesn't have that much power and torque in 1st and 2nd to get up to speed, and you would NOT save that much on petrol.


If you can't figure out the wiring on the above, there are many on this forum that can advise.

James
James Huggins

The only reason you won't save on petrol, is that you'll be keeping up with traffic for a change. But I tried hanging in the slow lane like I used to before getting OD, and I noticed a marked increase in efficiency, several MPG, plus a good healthy dose of peace and quiet.

Normally you just swap in the OD-equipped transmission complete. It very nearly just bolts right in. On late cars you'll need a speedo cable, and you'll need to wire in a switch... that's about it. I found the conversion to be much easier on my MG than on my Volvo.

So, to answer your question, yes, it can be done easily and yes, it should be done.
Sam Good

Give Quantum Mechanics in Madison, WI a call. They can set you up with an overdrive conversion on your gearbox, or sell you a complete unit. They are known to be experts on gearboxes and overdrives for our cars.
Steve Simmons

Hi,

Quick question here: I have a 1980 OD that I am going to put in my 78 soon and from what i have read, I know it only has OD available in 4th gear, which gets rid of the awesome use of 3rd OD for the twisties... my question is this--is it easy to mod it to handle 3rd and 4th gear and if so, will it hurt the OD unit or will all be wonderful as I blast down the road, flicking the switch to get the most out of that sweet sweet engine?

Thanks!
John

John Snider

You will be fine adding OD to 3rd (especially with the asthmatic US engine) the UK kept it to the end. It was only changed to 4th only for other reasons connected with the smog stuff. A different selector lever is involved, you may be able to fit an earlier one, or work out how to modify the existing.

FWIW the V8 *did* have OD removed from 3rd because of damage to the OD.
Paul Hunt 2

You could build up the ramp on the selector shaft with weld and grind it smooth but we can supply the correct part - www.octarine-services.co.uk
Chris at Octarine Services

This thread was discussed between 04/07/2007 and 17/07/2007

MG MGB Technical index

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