MGB Gearbox Conversion Kit 5 Speed Mazda - 3 Bearing Engine


Prices are exclusive of VAT

Built to order - Despatched 10-15 business days after order receipt
Product code VITMGB254


  • Fits exactly in place of your existing MGB gearbox
  • Improves feel and power delivery
  • Reduces weight of your MGB
  • Comes fully assembled
  • Gear ratios suit perfectly
  • Easily fitted by anyone who could fit a standard MGB gearbox
  • No drilling or cutting of your classic MGB
  • Full fitting instructions provided
  • Optional electronic speedometer
  • Period correct gear knob
  • High-quality OE Mazda parts
  • Built on brand new tried and tested MX-5 gearbox
  • Electrocoated parts


  • MGB Gearbox fitting service available in the UK
  • Worldwide shipping
  • 12-month parts defects warranty
  • Suitable for all 1962-80 MGB variants
  • In the USA or Canada? Visit our North America distributor Moss Motors


At Vitesse Global we have shipped our MGB gearbox right across the globe, delighting MG owners from the UK right to the USA, Canada and Australia. 

Give your MGB the perfect upgrade: improve your driving experience without losing any of the character you love.


What’s in the MGB gearbox kit?  

  • NEW Mazda MX-5 5 speed transmission with:
    • Vitesse gearbox case
    • Vitesse bellhousing
    • Vitesse machined billet front plate 
    • Modified rear case with Mazda mechanical Speedo drive assembly
  • Mazda MX-5 OE clutch friction plate
  • Bespoke shift lever and shift knob kept in original position
  • Concentric slave cylinder assembly
  • Braided clutch pipe and remote bleed pipe for easy bleeding
  • Prop shaft
  • Spigot bush with Mazda OE needle roller bearing assembly
  • Speedo drive cable and angle drive
  • Gearbox rear mount bracket assembly and Isolator
  • Complete geomet coated UNF fixings kit
  • Clutch alignment tool


Do I need an electronic speedometer for my MGB gearbox? 

As standard, we include a mechanical speedometer sender unit and cable in your kit, which fits to the original instruments in your MGB and does everything you need it to but for those looking to improve more than just your gear selection and power delivery, we now offer a Smiths electronic speedometer. 

  • Easy to install
  • Easy calibration
  • Saves on both cost and time of sending original mechanical speedo away to be re-calibrated
  • Bouncy needle issues eliminated

For more detail on speedometer calibration and a handy calculator, click here

What’s in the Smiths electronic speedometer kit? 

  • Mazda electronic sender unit fitted to the gearbox in lieu of the mechanical one
  • Wire harness with dedicated connectors at either end to connect to the sender and instrument
  • 4” (100mm) instrument for MGA and all chrome bumpered MGB’s. Note: Only available in negative earth form and cannot be switched
  • 3” (80mm) instrument for MGB GT V8’s and rubber bumpered MGB’s


Can I fit the MGB gearbox kit myself? 

In short, yes. Anyone who is confident in removing and installing a standard MGB gearbox will have no trouble fitting one of our kits, as everything has been specifically designed to match your vehicle - no bodges here! 

If, however, your mechanical skill stops short of gearbox installation, we’ve got you covered. We can deliver your new MGB gearbox straight to your chosen mechanic and speak directly to him (or her), should they have any questions regarding the install. 

If you are still unsure, take a look at our installation instructions


MGB gearbox reviews and features

Our MGB gearboxes have been fitted to MGBs all over the world and have gained a name for quality in the MG world, take a look at what MG Enthusiast and MGCC have said about their experiences with our gearboxes: 

MG Enthusiast feature

MGCC feature

Want to lighten the load? 

Our full alloy case means significant weight savings can be achieved with our MGB gearbox kit - up to 13.5kg! 



The perfect ratio: 

The standard MGB gearbox differential has a ratio of 3.909:1, identical to that of the MX-5 differential, meaning the gear ratios work perfectly in the MG. Furthermore, the standard gear ratios of the Mazda gearbox are similar to the Ford Type 9 close ratio gear set, which attracts a significant premium over the standard Ford Type 9 gearbox!

Gear Ratio - Mazda Transmission 
1 3.136
2 1.888
3 1.330
4 1.000
5 0.814


Still unsure about upgrading? Ask us anything about our MGB gearboxes 

We understand that committing to an upgrade of this magnitude on your classic car can be a worry. If you have any questions that are not answered above, be they big or small, just get in touch. These gearboxes were designed by our team and built right in the heart of the UK, in Hinckley, Leicestershire by us, so there really isn't much we don't know about them. 


Get in touch:

Tel: +44 (0)1455 611230


Or call us to organise to visit us and test our gearbox in our demonstrator MGB GT.


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