Gearbox change.

[Paul Amey]

I have read about various alternative gearbox's for Spitfire's etc. I am wondering if anyone has ever tried fitting a Mazda MX5  box in a Vitesse?

[johny]

Apart from the Vitesse box being relatively small it also has a tall first gear (which in my opinion could even be a bit taller) so its difficult to find an alternative box that wouldnt make first gear redundant. Even the large chassis Triumph box which, apart from being quite a bit bigger, doesnt have a suitable 1st gear ratio!

The problem is that the Vitesse and GT6 are relatively light while their engines are pretty torquey so the gearbox is basically a close ratio one...

[Clive]

18 minutes ago, Paul Amey said:

I have read about various alternative gearbox's for Spitfire's etc. I am wondering if anyone has ever tried fitting a Mazda MX5  box in a Vitesse?

Somebody on here has fitted one to a GT6, he may be along later. But a great deal of custom engineering is involved. 

T9 gearboxes have been fitted, and pretty good. But expensive and you need the long input shaft variety. 

And the first gear issue is important. In all honesty I would spend out and get a top end gearbox rebuild over an alternative (the exception is if you have access to mills/lathes etc, and can machine parts to allow a conversion)

[Mathew]

Look at rx8 gearboxes. Fitted one to my spitfire. Mine has a puma engine but a suitable adapter could be made. I have found it to be very smooth with a quick change. Mine is 5 speed, the six speed is exactly the same measurement. They are alot cheaper than t9 but have gone up since i got mine. Expect to pay 150 to 200 for one.

[johny]

For the Vitesse we're looking for 2.65 or lower 1st gear ratio and I think the RX8 5 speed unit is 3.48 and the MX5 is 3.14. Some of that can made up by changing the diff but theres a limit on the ratio that the 2L can pull in top gear especially with overdrive....

[Ian Foster]

 

13 hours ago, Paul Amey said:

I am wondering if anyone has ever tried fitting a Mazda MX5  box in a Vitesse

Paul

Indeed they have! (well a GT6 anyway)

It's a long story but appears to have a happy ending.

http://sideways-technologies.co.uk/forums/index.php?/topic/8925-mazda-gearboxes-some-bstard-told-me-it-was-impossible-so-i-had-to-do-it/

Ian

[Paul Amey]

Thank you for the help and advice.

 

Paul

[JohnD]

Paul,

No one has asked, Why?

Are you concerned for the reliability of the box?    I race with a GT6 one, rebuilt for me by Mike Papworth.   I know it's dangerous to say so, but it's never let me down!

If you want different ratios, which end?    Overdrive provides an easily fitted (but not just added to a non-OD gearbox) fifth gear option.

John

[Nigel Clark]

3 hours ago, JohnD said:

Paul,

No one has asked, Why?

Are you concerned for the reliability of the box?    I race with a GT6 one, rebuilt for me by Mike Papworth.   I know it's dangerous to say so, but it's never let me down!

If you want different ratios, which end?    Overdrive provides an easily fitted (but not just added to a non-OD gearbox) fifth gear option.

John

John,

What engine and what power/torque is going through your GT6 gearbox? I'm interested as I'm having a hybrid 1850 Dolomite box with J type O/D built for my 2.5 litre GT6 and seem to recall you run a 2.5 litre with Lucas PI in your racing Vitesse. If so, your experience seems reassuring.

I suspect the spec of my gearbox will be similar to your uprated GT6 box, where Mike P will have used a larger main shaft tip bearing.

Apologies for slight thread drift.

Nigel

[JohnD]

I don't know, because it has a new engine, just running it in, and no rolling road as yet.   BUt would hope for a tad more than 130bhp, a third more than the OE GT6.

Certainly, the gearbox mods you mention will make for a tougher 'box.    I did that for my fitst racing gearbox, and it stood up to it, until I stripped a gear - entirely my fault, not the 'box!  It was then I got Mike to build me one, with an 'up-rated' O/d oil pump.

[Nigel Clark]

2 hours ago, JohnD said:

I don't know, because it has a new engine, just running it in, and no rolling road as yet.   BUt would hope for a tad more than 130bhp, a third more than the OE GT6.

Certainly, the gearbox mods you mention will make for a tougher 'box.    I did that for my fitst racing gearbox, and it stood up to it, until I stripped a gear - entirely my fault, not the 'box!  It was then I got Mike to build me one, with an 'up-rated' O/d oil pump.

Thank you John. Chris Witor predicts 130-140bhp from the modified 2.5 litre saloon engine fitted to my GT6, based on the modifications I've made. On the road performance certainly suggests there's a lot more power and torque than a standard 2 litre. Once the stronger gearbox and O/D are fitted, I will make a trip to the rolling road and all will be revealed!

Nigel

[JohnD]

Where will you go, Nigel?

I can't find any RR in the North that will even claim they understand Lucas Pi!   I have used Denis Vessy before, but all he did was fiddle with the max fuel screw!

Revingtons have one and know Pi, and I thought to use the opportunity of a trip to Thruxton at the beginning of May (they are only 70 miles from there!)  but they are lockdown backlogged to the eyeballs, so probably can't fit me in.

But you may have carbs?

John

[Nigel Clark]

Yes, I have twin SU HS6, short dashpot from a Dolomite Sprint. Mark Field recommended Lynx, who are quite near me in Wellingborough:

http://www.rollingroadtuning.co.uk/

I've also used Aldon Automotive in Birmingham some years ago and was impressed with their capability. Don't know how much expertise they have with Lucas PI though. But they did find a couple more horses by fine tuning the advance curve on my TR6 PI.

Nigel

PS: More apologies for the thread drift.

[Steve P]

I went the big saloon box route on my 2.5 Vitesse with a 3:27 diff with a TR7 carrier.My engine was on the rollers when new and made 172BHP peak,can`t remember the torque number but it pulls like a train in all gears and will go up a hill in o/d 4th no problem.

Had to CV convert it as it snapped a driveshaft,diff and gearbox all good so far after 13k miles. I remember going down the Staines bypass a few years back giving it the beans,there was a guy behind me in a Jag XFR,when we stopped at traffic lights,he wound the window down and said"you must have a V8 in that".

S

 

[johny]

How do find 1st gear Steve? I wonder which ratio you have as I believe there are different ones...

[Nick Jones]

Torque is what kills gearboxes. So anything 2.5 will challenge the original Triumph offering which is marginal for the 2L. Yes, it’s a nice box when in good fettle with a sweet change and nice ratios, but not strong enough. There some things that can be done to improve matters to some extent with a bit of parts-bin raiding, but the other problem now is that there are very few NOS parts left, the repro parts mostly a bit dubious and the used parts in circulation have been circulating for a long time.....

In my experience, opening any 6 cylinder, small-chassis gearbox will reveal significant wear and or damage. Mainshaft tip, layshaft, inside of laygear cluster..... chunks off reverse gear, worn synchro hubs.... I dismantled three plus an 1850 single rail in an effort to gather enough parts for one decent working box and still had to cough up for a new mainshaft and have some machining done. The end result is a gearbox with the big mainshaft tip that actually works pretty well, just a bit noisier than I would like and an OD which is very slow to engage in spite of being fully stripped, cleaned and reassembled with new seals.  A disappointment after significant effort and expense.  This box is now surplus to requirements......

Ian has already linked to my MX5 box conversion thread on Sideways Tech forum. It’s in, it works, I’m using the car...... however there are several very good reasons why this is not a common conversion as you will see if you read the thread.  I have no idea whether this is the first/only one.

I understand Vitesse Transmissions in Hinckley are working on a conversion kit for the GT6/Vitesse based on the Mazda MX5 NC to add to their existing range, but I don’t think they are there yet.  If they can come up with one that is DIY fit-able by anyone competent to change a clutch (say), they will have done really well IMO.

Modified MX5 NA box in situ 

And with the unmodified tunnel cover fitted

Possible? Yes. Easy? Hell no!

Nick

[Steve P]

On 05/04/2021 at 12:43, johny said:

How do find 1st gear Steve? I wonder which ratio you have as I believe there are different ones...

It can be a bit short,depends where you go with the revs,it picks up quickly anyway so it doesn`t bother me.No idea of the ratio,bought the box from e bay and had Mike Papworth rebuild it.70 mph o/d 4th is about 2900 rpm,bit scary over 90mph as it needs a 4 wheel alignment.

The only issue i had was clutch geometry,i used a modified Vitesse flywheel and had to play with different bearing carriers to get it right,then it wore out the AP plate i was using in 10k miles,ended up with a paddle type and good so far.

Steve

[Rogues]

Hi Paul, just read your query regarding using a MX5 gearbox to a Vitesse. I have been in touch with Vitesse Global based in Hinckley, they have already fitted MX5 gearboxes to MGB's and various TR's but not yet in a Vitesse. However they are now finalising all of the components to make this happen, including new clutch, new prop shaft etc. I have visited their Unit and am very impressed with their set up and awaiting a call to arrange my gearbox to be replaced. If you require more details contact me direct. Roger

 

[DVD3500]

My Spit will be tested soon and we fear that we will be making over 100 HP and 110 lb/feet of torque... not sure the 1500 gearbox can handle it..

 

[johny]

They are about the figures for GT6/Vitesse and your gearbox is very similar if not stronger than the gearbox used in those however the ratios are different and you could find your 1st gear is now redundant. Also your clutch is quite a bit smaller so that might be the first thing to give especially if you start pulling away in second😵

[Nick Jones]

13 hours ago, DVD3500 said:

My Spit will be tested soon and we fear that we will be making over 100 HP and 110 lb/feet of torque... not sure the 1500 gearbox can handle it..

 

As already mentioned the 1500 single rail box is actually stronger than than the original 3 rail Vitesse/GT6 box in a couple of key areas, so no cause for great alarm. Gearing shouldn’t be too bad provided you stick with the original 3.63 diff, though first will be a bit short.

[thescrapman]

16 hours ago, DVD3500 said:

My Spit will be tested soon and we fear that we will be making over 100 HP and 110 lb/feet of torque... not sure the 1500 gearbox can handle it..

 

If you are kind to it, it will be fine.

same internals ( though not ratios) behind a TR7 4-speed. 

So just remember no "traffic Grand Prix" and definitely no drawing number elevens.

[DVD3500]

Mark Field had the box rebuilt before sending it to me so I reckon it is strong.

I will put a 3.63 in if I can't find a 3.27.

I plan mostly on cruising and  not doing drag races.... An there IS a section of non-speed-limited Autobahn near here....

[DVD3500]

20 hours ago, johny said:

They are about the figures for GT6/Vitesse and your gearbox is very similar if not stronger than the gearbox used in those however the ratios are different and you could find your 1st gear is now redundant. Also your clutch is quite a bit smaller so that might be the first thing to give especially if you start pulling away in second😵

I got a new heavy duty clutch from Mark Field as well as a billet fly wheel... I will try to be ... gentle..

 

[Steve P]

On 10/04/2021 at 19:46, DVD3500 said:

My Spit will be tested soon and we fear that we will be making over 100 HP and 110 lb/feet of torque... not sure the 1500 gearbox can handle it..

 

The new 1500 in my Herald made 92bhp on the rollers,it has a 3:63 diff and single rail o/d box,i`m more worried about the driveshafts as i snapped one before at the hub end on my Vitesse,not fun when your back wheel overtakes you.

Steve