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Nissan vs Mazda vs mgb mk11 4 speed O/drive

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MGB65B Avatar
MGB65B Gold Member Thomas Aczel
Sydney, Kurrajong Hts, Australia   AUS
1962 MG MGA MkII
1965 MG MGB "Dad's Little White Car"
Just a few comments to add:
1) The driveshaft length is the same for MGB Mk II overdrive and non-overdrive cars but it is NOT the same for MGB Mk I cars with and without overdrive. I think you will find you need the longer driveshaft from a Mk II car, or a Mk I with overdrive car, as your drive shaft is too short. You can also have your drive shaft lengthened to suit; we did for mine in 1986 when fitting a Mk I overdrive gearbox to my 1965 MGB, but finding a used correct shaft would be easier and cheaper.

2) The gear lever emerges 2" further rearward on the Mk II gearboxes than the Mk I gearbox, so the top of the tunnel needs modifying if you fit the Mk II overdrive gearbox.

3) You will need to relieve the tunnel a little near the driver's side (in RHD Australia) footwell to fit the Mk II O/D gearbox.

4) If you are using a mechanic who you are paying by the hour, the simplest of the alternative gearbox conversion is to buy a kit from Hi Gear Engineering in the UK. They use the compact Ford T9 gearbox which fits nicely into the tunnel of the MGB Mk I and the kit has everything you need, including the correct driveshaft, gearbox mounts, even speedometer drive cable. Your mechanic pulls one and replaces it with the other, so labour charges are minimised. You will not need to modify the tunnel or engine bay in any way.
I've got the Hi Gear Engineering conversion in my MGA, and it all went in exactly as supplied.
http://hi-gearengineering.co.uk/content/view/15/30/
But the Ford gearboxes are pretty old school now; they're a five speed conversion on the old four speed Ford Cortina box from the 1960's. More modern gearboxes would be nicer. But the T9 conversion is hugely popular. Hi Gear Engineering have sold thousands now. The Moss kit referred to above is supplied by Hi Gear Engineering.

5) Lots of people in Australia fit Nissan gearboxes and use a Dellows bell housing. Great if you are handy, but if you are using a mechanic the labour
charges go up as the mechanic fiddles to modify and adapt. But the gearboxes are plentiful and cheap at motor wreckers. Dellows have been around a long time.

6) The Mazda gearboxes would have the nicest action of them all, but the Vitesse kits are not cheap. And from what's written above, you'll again need tunnel modifications. Again Delllows should be able to assist with an appropriate bell housing.

7) The Mk II gearboxes with overdrive are wonderfully durable compared to the MK I gearboxes. They shift nicely too. I think they "feel" nicer than the Ford T9 gearboxes, and flicking in and out of overdrive is "cool". And they remain a genuine MG item.
If you go this way, you can get the wiring sub harness from Vintage Wiring Harness in Victoria. The owner, Paul Vermont, is a real MG enthusiast, owning several. His looms are perfect, indistinguishable from original, and very fairly priced.
https://www.vinwire.com.au

8) The other very easy conversion is what I did, fitting a Mk I 3 synchro overdrive gearbox. You need a wiring sub harness and a longerr drive shaft. Everything bolts straight in as the cars were designed for them in the first place. I personally love the mechanical vintage feel of the 3 synchro gearbox. But neither the gearbox nor the overdrive is as durable as the later four synchro gearbox and reproduction replacement gearbox parts have been of poor quality over the years. Original BMC/BL replacement parts have pretty much all been used up now. Similarly there are now very few Mk I overdrive gearboxes around. When they occasionally come up they go for about twice the asking price for a Mk II overdrive gearbox.

9) As others have said, fitting an overdrive or a five speed gearbox conversion will add to the pleasure of using your car in modern road conditions hugely. Definitely worth doing.

10) Consider joining your local MG car club. You are likely to find members who've done such work and can advise. Alternatively there are several MG specialist workshops around Sydney, such as MG Centre in Sydney which is owned by Stuart Ratcliff, who was till recently the Sydney MG Car Club president for many, many years.
http://www.classiccargurus.com.au/MG_Centre_of_Sydney
The Canberra MG Car Club, which would be closer to you is excellent, with many enthusiastic members. I'm sure you'd find excellent support and advice there.

Edit: sorry, just noticed you already have the four synchro gearbox fitted. With this already in you'd have the correct driveshaft and the tunnel modifications done already. I'd go with the MG overdrive gearbox. You just need the sub harness and the switch + escutcheon for the dashboard (again reproduction not as nice as the originals).
Edit #2: as Chris pointed out, the Mk I 3 synchro overdrive gearbox is shorter than the non-overdrive box and needs a longer tail shaft.
Edit #3: as per Edit #2.



Edited 3 time(s). Last edit at 2019-03-13 02:57 AM by MGB65B.

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dickmoritz Avatar
dickmoritz Platinum Member Dick Moritz
Philly 'burbs, PA, USA   USA
1) The driveshaft length is the same for MGB Mk II overdrive and non-overdrive cars but it is NOT the same for MGB Mk I cars with and without overdrive. I think you will find you need the shorter driveshaft from a Mk II car, or a Mk I with overdrive car, as your drive shaft is too long. You can also have your drive shaft shortened to suit; we did for mine in 1986 when fitting a Mk I overdrive gearbox to my 1965 MGB, but finding a used correct shaft would be easier and cheaper.

I believe the OP said that he had already converted his car to a 4-synchro non-overdrive gearbox. If that is the case, he can continue to use the same driveshaft if he converts to a 4-synchro overdrive gearbox...

Dick



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

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tvrgeek Avatar
tvrgeek Scott S
Hillsborough, North Carolinia, USA   USA
1965 MG MGB
Maybe OD is easiest and most economical, but I have had them in a Spit and Volvo and I much prefer a 5-speed. Preference. Slightly lighter but not a factor in a street car.
ODs do have things that fail like to HP valve.



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dickmoritz Avatar
dickmoritz Platinum Member Dick Moritz
Philly 'burbs, PA, USA   USA
It's not just a High Pressure valve, since the assembly also incorporates a low pressure bleed to provide oil to the third motion shaft. I have rebuilt scores of MGB overdrives and have never seen a pressure valve fail other than physical damage by ham-handed "mechanics"...

Dick




In reply to # 3907497 by tvrgeek Maybe OD is easiest and most economical, but I have had them in a Spit and Volvo and I much prefer a 5-speed. Preference. Slightly lighter but not a factor in a street car.
ODs do have things that fail like to HP valve.



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

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olbrowneye Paul Brown
Goulburn, NSW, Australia   AUS
Thanks Thomas I’ve actually got the Canberra MG, Club,membership forms for myself & a fellow 1970 mgb owner here in Goulburn, I think cost wise and originality I’m steering towards the O/Drive box, I appreciate all information that I’ve received within the last 24 hrs, what a great forum site,with so much information, expertise in all the aspects of the MGB,
I will certainly be looking into the other links you have given me Thomas
Cheers everyone �

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olbrowneye Paul Brown
Goulburn, NSW, Australia   AUS
Yeah for me at the present time the original o/drive box is looking like the go,to suit my budget.
I have a later mk 11 fully synchro 4 speed box , so I’m lead to believe drive shaft is ok and that it has been modified by previous owner that the tunnel was extended length wise as it’s that bit longer in the gear shift change .
So that all said $1200. vs kit form @ purchase cost $5800au. It’d be more of a want & not a need, who knows I might get lucky � in tonight’s lotto, good on yer mate for your input let you know how I go
Cheers � Paul Olbrowneye

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olbrowneye Paul Brown
Goulburn, NSW, Australia   AUS
Thanks Terry, yeah I think I’m going with theO/Drive, for originality and cost, & I don’t have to change drive shaft etc.
I have the O/D, switch only need wiring loom ! And there’s a contact in Victoria where I can source one.
Cheers mate !
Paul olbrowneye

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olbrowneye Paul Brown
Goulburn, NSW, Australia   AUS
Yeah thanks Kelvin, think I’m going with the original o/drive box for originality.
Cheers � olbrowneye

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humbucker Avatar
humbucker Silver Member Paul Whitworth
Toronto, NSW, Australia   AUS
1967 MG MGB MkI "The MG"
There is a fourth option.

You can, as I did, install a Toyota 5 speed Celica box (W52). I have a MkI MGB which had the 3 synchro box.

Dellows in Sydney sell a bell housing to suit this upgrade. Also a new rear gearbox mount and Toyota clutch plate. You use the MG pressure plate (or fit a new one)

The bush in the crankshaft has to be changed to suit the Toyota input shaft.

Dellows can also supply diffenet slider kits to change the position of the gear lever. Mine comes up in the exact same place as the original MG gearbox.

The tailshaft is a custom made hybrid made from a Datsun Sunny drive shaft as it will mate with the MG diff.
The drive shaft is shortened and a Toyota front uni and yoke is welded on to suit the Toyota gearbox.

I was able to source a gearbox at the wreckers from a 1980 Celica (steel case W52). $300 and came with the rear yoke. No modifications are necessary for clearance.

Dellows also supply a speedo adaptor to connect the MG cable to the Toyota box. All up it cost around $1000. ($300 for gearbox and $700 for Dellows parts.) Ire-fitted the pressure plate as it was not that old.

The clutch slave cylinder bolts straight onto the new bellhousing which is for the MkI backing plate and has the hole for the inertia starter.

This upgrade really transformed the car.

Cheers!

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olbrowneye Paul Brown
Goulburn, NSW, Australia   AUS
Thanks Paul, that’s great information never thought of the old Celica 5 speed I remember Dellows, from the early 1980’s 4 speed box into early falcons
Thanks for jogging my memory
How long ago did you do the conversion? and is Dellows still in the Bankstown airport area ?
How easy was it to source a Celica box ?
Cheers � Paul olbrowneye

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sweep Avatar
sweep Gold Member Chris W
Gosford, NSW, Australia   AUS
1966 MG MGB "Basil"
2013 Volkswagen Tiguan
2015 Audi A3
Thomas, I think you'll find you've made an error with regard to the Mk1 tail-shaft lengths - or I'm misunderstanding.

The tailshaft for the Mk1 OD G/B is actually longer than the Mk1 nonOD G/B. I know this for a fact 'cause when I swapped in my OD I used a spacer to use the shorter shaft with the OD box.

Counter-intuitive, but true.



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humbucker Avatar
humbucker Silver Member Paul Whitworth
Toronto, NSW, Australia   AUS
1967 MG MGB MkI "The MG"
Hi Paul,

Well it was 2004 and back then it was pretty easy to find a Celica box at the wreckers. It might be harder now! My first choice was a Supra 5 speed W55 alloy case which I bought on E-Bay for $200. Dellows said it would require mods to the floor and transmission tunnel as it is a wider box than the steel case. So I bought and fitted the steel case and sold the Supra box.

The box came out of a pretty high mileage car but I did not rebuild it before fitting it. I just drained the oil and rinsed it out with Kerosene. It does have a slight bearing noise but I haven't put a spanner on it except to change the oil.

https://dellowconversions.com.au/product/toyota-2t-5-speed-split-alloy-case-to-mgb-mk1-manual-bellhousing/

It seems they only cater for the split case T50 gearbox from the Corollas now.

The steel case I have was good for 300HP apparently and was a common fitment to Ford and Holden V8s.

Cheers!


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MGB65B Avatar
MGB65B Gold Member Thomas Aczel
Sydney, Kurrajong Hts, Australia   AUS
1962 MG MGA MkII
1965 MG MGB "Dad's Little White Car"
In reply to # 3907856 by sweep Thomas, I think you'll find you've made an error with regard to the Mk1 tail-shaft lengths - or I'm misunderstanding.

The tailshaft for the Mk1 OD G/B is actually longer than the Mk1 nonOD G/B. I know this for a fact 'cause when I swapped in my OD I used a spacer to use the shorter shaft with the OD box.

Counter-intuitive, but true.

Oops Chris you are right. My drive shaft/tail shaft/propellor shaft was lengthened and not shortened!
I agree it’s counterintuitive but the 3 synchro overdrive gearbox is shorter than the non-overdrive box.
I’ll do yet another edit to my post. Can’t have me saying incorrect things! angry smiley

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sweep Avatar
sweep Gold Member Chris W
Gosford, NSW, Australia   AUS
1966 MG MGB "Basil"
2013 Volkswagen Tiguan
2015 Audi A3
Yes, but I get a buzz when I am able to correct The Master! grinning smiley

In reply to # 3907862 by MGB65B
In reply to # 3907856 by sweep Thomas, I think you'll find you've made an error with regard to the Mk1 tail-shaft lengths - or I'm misunderstanding.

The tailshaft for the Mk1 OD G/B is actually longer than the Mk1 nonOD G/B. I know this for a fact 'cause when I swapped in my OD I used a spacer to use the shorter shaft with the OD box.

Counter-intuitive, but true.

Oops Chris you are right. My drive shaft/tail shaft/propellor shaft was lengthened and not shortened!
I agree it’s counterintuitive but the 3 synchro overdrive gearbox is shorter than the non-overdrive box.
I’ll do yet another edit to my post. Can’t have me saying incorrect things! angry smiley



The secret to creativity is knowing how to hide your sources.

To the intelligent person, life appears infinitely mysterious, but the stupid have an answer for everything.

Day Dreamers, don't discourage them. That's where original thought comes from.

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tvrgeek Avatar
tvrgeek Scott S
Hillsborough, North Carolinia, USA   USA
1965 MG MGB
If I found a Celica 5-speed I would not need to convert the bell housing, but happily put the 20R in along with it! Just about unobtainable around here. Seems they all get shipped to South America to keep their fleet of old trucks running.

Tail housing lengths are different as are the diff nose. Banjo vs tube.



Cogito ergo sum periculoso

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