MGB Gearbox Conversion Kit 5 Speed Mazda - 5 Bearing Engine - Remanufactured


Prices are exclusive of VAT

Built to order - Despatched 10-15 business days after order receipt
Product code VITMGB258R


  • Replaces your existing gearbox without modification
  • Improves driveability with smooth, precise gear changing
  • Reduces weight
  • Comprehensive conversion kit
  • Gear ratios suited perfectly to the MGB
  • Easily fitted by the home or professional mechanic
  • No drilling or cutting of your classic MG
  • Full fitting instructions provided
  • Optional electronic speedometer
  • Period correct gear knob 
  • Electrocoated brackets and fixings supplied
  • Gearbox fitting service available in the UK
  • Worldwide shipping
  • 12-month parts defects warranty
  • Suitable for all 1962-80 MGB variants


Vitesse Global has now shipped thousands of gearbox kits around the world, providing reliable and enjoyable motoring for MG owners worldwide. 

Our gearboxes offer the perfect upgrade for your MGB, improving your driving experience without losing the character you love.

What’s in the kit?  

  • Fully Remanufactured 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 gear lever and gear 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 electroplated UNF fixings kit
  • Clutch alignment tool


Do I need an electronic speedometer? 

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 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. 

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 13.5kg! 





The perfect ratio: 

The standard MGB 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! 

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 even test our gearbox in our demonstrator MGB GT.





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