MGB V8 5 Speed Mazda Gearbox Conversion Kit


Prices are exclusive of VAT

Built to order - Despatched 10-15 business days after order receipt
Product code vitmgb251V8


  • Fits exactly in place of your existing MGB V8 gearbox
  • Improves feel and power delivery
  • Reduces weight
  • Comes fully assembled
  • Gear ratios suit perfectly
  • Easily fitted by anyone who could fit a standard MGB V8 gearbox
  • No drilling or cutting of your classic MGB V8
  • Full fitting instructions provided
  • Optional electronic speedometer
  • Built on brand new tried and tested MX-5 gearbox
  • Period correct gear knob 
  • Electrocoated parts


  • Gearbox fitting service available in the UK
  • Worldwide shipping
  • 12-month parts defects warranty
  • Suitable for all MGB V8s, including conversions
  • In the USA or Canada? Visit our North America distributor Moss Motors


For a number of years now, Vitesse Global has shipped its MGB V8 gearboxes around the world, delighting MG owners from the UK right to the USA, Canada and Australia. 

Our MGB V8 gearboxes offer the perfect upgrade for your MGB V8: improving your driving experience without losing any of the character and charm you love.


What’s in the MGB V8 gearbox kit?  

  • NEW Mazda MX-5 5 Speed Transmission:
    • Vitesse Gearbox Case
    • Vitesse Bellhousing
    • Vitesse Machined Billet Front Plate
    • Modified rear case with Mazda mechanical Speedo Drive Assembly
  • Bespoke Clutch Friction Plate
  • OE Clutch Cover
  • Bellhousing Dirt Shield
  • Bespoke Shift Lever and Shift Knob kept in original position
  • Concentric Slave Cylinder Assembly
  • Braided Clutch Pipe and remote Bleed Pipe for easy bleeding
  • Bespoke 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 V8? 

As standard, we include a mechanical speedometer sender unit and cable in your kit, which fits the original instruments in your MGA 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


Can I fit the MGB V8 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 gearbox straight to your chosen mechanic and speak directly to him (or her), should they have any questions regarding the install. 

Alternatively, for those in the UK, we are able to offer a full MGB V8 gearboox fitting service at our facility in Leicestershire.

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


Reviews and features

Over the years our gearboxes have been fitted by some of the biggest names in the MG scene, 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 this kit, up to 23kg compared to the R380!



Vitesse MGB V8 Kit Weights


The perfect ratio:

The standard MGB V8 differential has a ratio of 3.07:1, so the gear ratios work perfectly in the MG, utilising the extra torque delivery of the V8.

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! 

Over the years, we’ve had all kinds of questions: ‘will it fit x?’ ‘what about connections to this or that?’ ‘can I fit your gearbox to Y?’. Whether you’re super technically minded or really don’t know a spline from a bellhousing and want a gearbox shipping straight to your mechanic, we’re here to help!

Drop us a line on:

Tel: +44 (0)1455 611230


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

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