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MG MGB Technical - Mazda 5 speed gearbox conversion

I am building a very nice mgb roadster into a heritage shell.

I would be interested to hear what you guys think about the Mazda gearbox conversion against an overdrive box.

Do you think it would add value?

I need to strip and check the overdrive box, and it will probably need the overdrive servicing anyway, so I will have significant costs anyway.

Yes I know it is not original, but a better driving experience?

Thanks

Colin
Colin Parkinson

Colin
I have T9 Ford 5-speed box in my MGA, I don't think it actually adds any value to my car although it does improve the driving experience no end. Mainly because the standard MGA gearbox only has 4 gears and has no synchro on 1st gear.

Your MGB has overdrive on 4th and 5th and so you already have the 5th gear and so there isn't all that much practical difference between a 5 speed and your O/D box.

I would quite like the quirkiness of the O/D box and so I personally would keep with it.
However, if you are having to replace the gearbox anyway, it may be worth comparing the price difference to see which is the most economic option.

Hope that helps
Cheers
Colyn
Colyn Firth

Having had both o/d box and 5-gear boxes I prefer the 5 gears. With o/d you need to keep the load on it for engaging and disengaging this means keep your foot on the accelerator when you'd normally be braking/changing down a gear to slow up.

O/d on third is nice for flicking in and out of when pressing on with spirited driving.

If you look at the Archives here and in the midget Technical section you'll find threads/posts on 5-speed conversions and Mazda gearbox and conversions, the pros & cons.

Depending on the o/d and gearbox you can get 6 ratios rather than 5 but you also need to look at the ratios of any set up (someone put up access to a spreadsheet for ratios, take 3% off the tyre diameter if you want to allow for rolling circumference).

I had a Mk2 MX-5 and the gear changes on that were so sweet and better spacing (ratios) too than the '74 BGT I had (with o/d).
Nigel Atkins

I much prefer the original as it gives you six gears, and anticipates the paddle change that is seen as so desirable these days. You don't HAVE to keep your foot on the throttle, it depends what the revs are when switching out. Lowish revs on a trailing throttle can give a jolt, but other than i.e. almost idle or higher revs less so. When building speed it would be normal to keep the power on when switching in or out.

It also depends on the shimming of the relief valve - more shims give sharper engagement and disengagement, less give softer. But it's all in the eyes of the beholder. £2500 for a Mazda conversion is not something I would ever do.
paulh4

My personal view is that I would rather have the 5-speed any day. The overdrive is a complicated way to solve a simple problem. With the age of the units now, it is likely to be less reliable than a good 5-speed, and the Mazda box is a VERY good 5-speed with one of the slickest changes in the business. As for adding or subtracting value, I wouldn't know, nor would I care.
Mike Howlett

I think these conversions are fine if they can be done with the minimum of unique wear and tear parts such as clutch components and use of off the shelf u/js etc. Another aspect is availability of gearboxes: MGB ones still seem readily available, hopefully as will MX5 ones, because of the long production run, but I've heard that folk now have more difficulty (cost!) in obtaining the Ford Type 9.
Peter Allen

I forgot the add value.

I'd think with a Heritage shell build you could stick with "originality" to keep value up or if you're doing a lot of changes/upgrades/improvements/modifications/customising then the change of gearbox would as part of the whole package increase value but you'd probably need to do quite a lot of good changes that might appeal to a younger or different set of buyers prepared to pay more for a car that's not a static show piece.

For value on original type cars it is ALL about cosmetics/appearance how well they perform is of very little consequence. This may also be the case for a modified car but it's more likely to be driven and harder on at least the odd occasion so initially performance matters too.

I personally would be wary of the six-speed only as a friend in the club had a lot of trouble with that when he bought a new MX-5, sometime in the '00s, and engine problems, blamed me as I'd recommended them.
Nigel Atkins

Nothing wrong with the Mazda 6 speed Nigel, a lot stronger than the 5 spd --The MX5- 6 speed is the same box that the RX8's and some Nissan's use---it is a bulkier box though-
Good for probably 250HP safely but with a 5spd 200 pulls them up, Ok if converted to a dog box but if used with good power as they are they rip the synchro gears off the side of the drive gears
Had a B with od box that I ran in hillclimbs years back and found that in 2nd gear if the od was switched on, by pulling the g/lever over to the right it would pick up 2nd od
Quite a handy gear for splitting 2-3 uphill

A 5spd Mazda box in a B is a nice conversion
Just a matter of do you want it semi original or not

willy
William Revit

Fair enough Willy, just Sod's Law then the only 6 speed I heard about (more than once as I'd suggested the model) was a rare wrong un - but the engine sounded worse, something to do with SAAB? or Volvo? or my poor memory.

As the owner of a current Heritage shelled Midget and previously a Heritage shelled Spridget and a r/b B roadster V8 conversion I can say originality is relative and can be interpreted in more than one way.
Nigel Atkins

All good Nigel
And I agree with the MX5 engine, they're a good little engine in std trim but a bit of a grenade with some pressure on them
William Revit

Its a funny thing, many people didn't like the idea of putting the Ford T9 gearbox into the MGA because it was a non MG gearbox. It was ok though to fit an MGB overdrive gearbox because it was an MG part.

The problem is that to fit the overdrive box into the MGA you have to cut out the rear gearbox mountings and then fabricate and weld in new ones to fit the box. So it is not a simple job (unless you are welder)

To fit the Ford T9 box from Hi-Gear Enineering is a much simpler process, you just have to drill 4 holes into the floor brackets to mount the box.

So ironically, you could really say that by fitting a Ford box, I have actually kept my MGA more original than it would be if I had fitted the MGB box.

If you do decide to go the 5-speed gearbox route, both the Ford T9 box and the Mazda Miata box are lovely to use, great gear-changes and synchro on 1st too.
I believe that the ratios on the Mazda box are more evenly spread compared to the Ford box.

The standard Ford box has a large gap in ratio between 2nd and 3rd gears just like the original MGB box.
I found this a bit annoying with a standard-ish 100 bhp engine when I was climbing long steep hills, the engine would begin to labour a little in 3rd gear, but when I then changed down to 2nd gear, the engine was then revving away at 5000 rpm and above.

The higher 2nd gear in the Mazda box would help here quite a lot.

I can provide some info on the gearbox ratios of these gearboxes if anyone would like them.

Cheers
Colyn
Colyn Firth

Whilst understanding what Colyn has put I'd stick with the original choice of MX-5 or O/D.

The MX-5 box, I had, had lovely sportscar changes, but sorry I disagree, the T9 has not, in fact I'd say the T9 is very much family saloon style feel.

I have a T9 in my Midget, and sorry again, disagree about the gap between 2nd and 3rd on the standard T9, well remembering the gap on my '74 BGT between 2nd and 3rd. I find the standard first gear to be a bit low, but good for the reduced torque of the A-series for steep hill starts.

I've tried to improve the feel with the use of a quick shift (sports) lever which reduces how far the lever moves about in the limited cabin space, but being unbushed they tizz annoyingly at around 3,500 revs, spot on 70mph for me. I now have a shortened Ford Sierra lever but still practically have to open the passenger door to engage reverse.

T9 and, at least AFAIK the earlier, Mazda boxes benefit from using Castrol Syntrans Multivehicle gear oil.

The T9 isn't a bad box, and generally considered very robust, but I was disappointed to learn when returning to classic MGs that the Toyota conversions were no longer available.

There's a thread in the Midget section where a chap done his own Mazda box conversion to a Spridget that may over some points.
Nigel Atkins

Nigel
Tried everything to stop a straightcut T9 quicky buzzing and found that if you remove the gearlever and pull the spring off and pull the lever out of the swivel ball, then fit a thin, (around 2mm)flat rubber washer between the face on the lever and the bottom of the swivel and then reassemble it 90% of the tizz goes away, well, can't hear it over the gear noise anyway---ha ha
willy
William Revit

Willy,
wouldn't the washer push the stick against the bearing more?

Have you tried the igus igubal spherical bearing (EGLM-20) instead of the standard steel bearing, much smoother and slicker feel to the lever movement and gear change.

(igus bearing shown in middle of image below)



Nigel Atkins

Hmm- the one we get here from RF (DRT024)just has a metal sphere, It's a heavy duty race lever , the washer goes between the top of the step on the lever and the bottom of the sphere--I guess the spring is preloaded another mm or two when it's back together but having the rubber insulating the lever from the bottom of the sphere seems to do the trick
William Revit

Willy,
actually the best change I made was instead of using the black plastic Ford or aftermarket saddles which soon seem to wear and give slop is instead to use the heavy duty gear lever saddle clip. These clips are cheap, easy to fit, and give a more positive and nicer feel to the change and are hard wearing. These are much better for road cars and might be better in race cars than the brass ones but I wouldn't know.

https://www.ebay.co.uk/itm/FORD-TYPE-9-GEARBOX-ESCORT-CORTINA-CAPRI-SIERRA-H-DUTY-GEAR-LEVER-SADDLE-CLIP/152915422682?hash=item239a782dda:g:DrwAAOSwlpZai98P



Nigel Atkins

Nigel,
maybe the gap between 2nd and 3rd isn't a concern if you don't spend so much time climbing long alpine mountain roads.
Also, I suppose it depends on just how much torque your engine produces, my 3-brg MGB engine obviously didn't have as much torque as some other similar engines, I have a feeling that the fast road cam it had was part of that problem.

When I decided to do something about improving the Alp climbing power of my car a couple of years ago, after first considering fitting a supercharger, I eventually decided to swap to a 1950cc 5-brg MGB engine.

At the same time I decided to upgrade the Ford T9 5-speed box and so I fitted uprated bearings and fitted extra high ratio 1st and 2nd gears.

This has made the ratios much closer and there is definitely now no large gap between 2nd and 3rd gears.

But, in retrospect, I probably could have got away without doing the expensive gearbox work.
Because this new engine has so much torque and bhp that it almost doesn't need 1st and 2nd gears.

It will now strongly accelerate up virtually any steep road in 3rd gear, in fact, I have occasionally set off from a standstill in 3rd gear and the engine has coped with that. It pulls away with no complaint, no obvious pinking, just leaving me to wonder why it feels a bit more sluggish than usual! :-)

If I was having to fit a new gearbox to an MGB I would first look at the Mazda because it it is a lovely gearbox and has the best spread of ratios.

But as I said previously, I do like the quirkiness of the MGB overdrive box and so if it was fixable, I would probably stay with it.

My Ford T9 box does have a lovely gear-change action, its a bit like a switch and I am really happy with it. I suppose the boxes must all vary.
It doesn't "buzz" either.

The complete Hi Gear engineering 5-speed kit including the std box will cost you £2100 inc VAT
(plus about £300 more if you have the close ratio version)

The Vitesse kit will cost you £2874 inc VAT and so, if you include the cost of uprating the T9 box, the prices are pretty much the same.

Cheers
Colyn
Colyn Firth

olyn,
as you say the power range, low down torque and overall gearing make differences to how things feel and behave.

The gap between 2nd and third on the T9 is less than either of the standard boxes in the B.

For Colin's project we're agreeing on Mazda or O/D and discounting T9, my preference would be Mazda over O/D.

We can't agree based on our experiences about the T9 box, your box must be very good to be like a switch, my experience is that the box in my Mk2 MX-5 was much more like that than the few T9s I've ever driven.

Sorry if I wasn't clear (agin, as usual) I meant the buzz/tizz is with using the quickshift gear lever as it lacks the big isolation rubber block the standard Ford gear lever has.

By using the quickshift lever with the igus bearing instead of the standard steel bearing plus using the red heavy duty saddle clip the T9 shifts were much better - but the buzz/tizz remains and whilst the range of lever movement is reduced (25%?) it's not really quicksh*t, on mine at least, as the synchos have to catch up.

Unfortunately I've missed out, so far, on long Alpine mountain roads, I'd really love to drive on them especially the ones that get less traffic and Top Gear type tourists. I do though love going up mountain roads, not so much down, and have in a few different places in a few different cars. I can recommend doing so in a two-seater sportscar which has the RV8, standard power and standard gearing would be fine, as you can concentrate on steering and views.

Image of shortened (so straight too) Ford Sierra gear lever with red (glass reinforced?) heavy duty saddle clip.




Nigel Atkins

Nigel
Have you noticed that you only have to touch the gearknob and the sound changes
If you take the knob off the noise dramatically reduces
I think the noise gets amplified through the knob--R/F sell a special knob for their H/D quickshift but it's white----why?
We spun up an aluminium one and I think it was quieter, maybe a steel one with some mass to it could be the answer
I noticed in the pic. that the gearlever has one of those rubber insulators on it, you'd think that would have to do the trick
The R/F lever we have is just a straight (tapered) shaft-no insulator
Cheers
willy
William Revit

Willy,
I can't remember if I've gone knob less but I'm sure I should have. Mine has special insulation material (blu-tac). I've never tried the quickshift with the gear knob lock nut fitted so perhaps I should.

I have in the shed a gear knob from a Ford Sierra but to me it's the wrong shape and feel for a sportscar.

The black gear lever in the last photo is a cut down and straighten lever from a Ford Sierra and doesn't tizz.

Over here you can get better made quickshift levers than the cheap one in my first photo, that came with my very expensive gearbox conversion. There's one that uses the igus bearing already, another that's twice the price of my cheap one but cautions that it will rattle (as they're for sport use) and they do a couple of solid gear lever knobs but again I don't like the feel of them and have learnt not to have metal before, too hot in an open car in the summer and initially too cold in winter.

I probably get more tizz on my gearbox as the remote was badly shortened by the specialist expert company and getting into 5th is a bit notchy - note the wear mark on even the red heavy duty saddle clip in my first photo.

Colyn,
apologies, the tide must have went out on my keyboard.
Nigel Atkins

ETA: I've just noticed my misspelling in my previous post to Colyn, it wasn't intentional but the result of the site alteration made me smile anyway - >> quicksh*t <<.
Nigel Atkins

I have a stupid question...all this conversation about the different 5-spds from do they all use the same bellhousing if so which one and if not which for each? I have a WC GM 5spd that I would love to put in a my 66 but can't find the info I need.
K Mudd

Mr Mudd, the Ford based 5 speed conversion from HiGear uses their own bell housing depending which car it is for, and the Mazda conversion from Vitesse uses a unique gear case and bellhousing assembly for each model.

Could you make an adaptor plate between your GM bellhousing and the B? Or machine off the flange, and weld on another as an adaptor??

Colin
Colin Parkinson

KM
That T5 you have is a fairly large box, bit of an overkill for a 4cyl. MG--I've had one in a V8 conversion but it was the Ford version which has a much shorter input shaft
I know why you want to use it, they are a good box
Dellow here do bellhousings for Rover/Buick/ Leyland V8 to T5 (Tremec) boxes
Your best bet would be to adapt your GM bell to the MG rear plate if you were to go ahead with the swap
There is an issue with the gearchange housing though, it is fairly high above the box and the floor(tunnel) has to be cut out to get it to sit properly
I'm a bit concerned that the extra length of the front shaft will sit everything too far back though, you'd need to measure both the MG and your box from the front of the bell to the gearstick to see
As I mentioned the one and only that I've done was aV8 with the engine moved back and the short box so can't really give you any definate answers

willy
William Revit

This thread was discussed between 31/08/2019 and 07/09/2019

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