Norton Commando 6, 5, & 4 Speed Gearboxes

Posted by Scot Wilson on

It has been said that at BritIron & Italianiron Classics, let us "Fuel Your Race Passions" is not just a slogan but a commitment, whether you are building a vintage TT racer for competition, a Ducati F1 vintage street bike or a classic Manx or Norton Commando racer. As a result, we are focused on and primarily committed to supporting the sport of Vintage Motorcycle Racing worldwide. Maintaining a quality offering is our most important goal. Our race spec items are race tested for quality, for assurance of structural integrity, for performance, for light weight, and for reliability. We also strive to maintain a "race team mindset" where we preserve the core of the machine but work to enhance performance and safety through the advances in available modern technology. As a result, we are extremely excited to offer 6, 5 and 4 speed gearboxes for Norton Commando twin cylinder racers and street machines by TTI. They have been providing racing gearboxes for the Molnar Manx racers over the past 10 years and with stellar results. Shown below is a Magnesium example of the 6 Speed Racing Gearbox for Manx racers.

We are also excited to offer the 6 Speed AMC Sand Cast Aluminum Alloy Gearbox for the Norton Commando racers who wish to use that torquey Norton power delivery while reducing the gaps between shifting ratios when "nailing it" on the twisties!! Link is shown above. This gearbox is equally comfortable on the track or the street and available with a kick start mechanism for standard Norton kick-start levers. For the past 10 years, we have used the TTI gearbox on our Manx racers without a single failure!! All of the TTI gearboxes are manufactured in New Zealand and include the same expertise for the Norton Commando racers as well as the Manx racers that we support. Bruce and the TTI team use a modern drum selector mechanism for a positive change with reduced pedal travel, stronger shafts & bigger bearings. As a racer, you have a choice of “Commando” or “Manx" mainshafts based upon your application. (Note that the sprocket offset of the Commando configuration is 3mm further outboard) There is also an option for lever direction. Do understand that your actual pedal or linkage may be unique to your application. We are happy to communicate about your application at as these gearboxes are built to your specifications. Shown below is our AMC Sand Cast Aluminum Alloy Gearbox for either 6, 5 and 4 speed structure.

Improve performance and reliability by installing one of our TTI 5 Speed AMC Gearboxes or a TTI 4 Speed AMC Gearbox that are built into the AMC Sand Cast Aluminum Alloy units as shown above. Whereas I will not be racing my Norton 920 cc JPN, it was my determination that a 6 speed gearbox would not be as effective on the street to justify the cost for my application. Therefore, I have decided that using a TTI 5 Speed AMC Gearbox would be the ideal application for maximizing the use of the torque of this large Commando engine with a unit with greater performance, reliability and better shifting ratios!! Further, the "standard" TTI 4 Speed AMC Gearbox is available and good up to around 90 BHP but beyond that we recommend the 5 speed version. Bruce and the TTI team use the same modern drum selector mechanism for a positive change with reduced pedal travel, stronger shafts & bigger bearings in these applications as well. Either of the 5 speed or the 4 speed gearboxes can be offered with a kickstart shaft at an extra cost for the standard Norton kickstart lever. Please also note that whereas there are options for a "taller" first gear to achieve a closer ratio box, we really do not recommend it due to the challenge of getting off of the line quickly. We find that our first gear internal ratio creates a better result "off the line" as it is closer to the original Norton Commando road gearbox of 2.556.

We are excited to offer our Billet Aluminum Oil Union Junction Block that replaces the OEM soldered block and shown above. Our unit with the fittings on the oil lines will allow for easier fitment and set up. The result of using this higher quality unit is that there will be less chance of breaking and leaking. Our Junction Block is tapped 1/4 BSP for unions or screw in hose connectors to suit your desired hose size. However, 1/4 - 1/4 Stainless unions can be supplied as an option. Further, the Union Block can be purchased without the stainless unions for a savings of $22.00. Please advise when ordering. Our kit is a direct fitment to the original Norton Commando crankcases as well as our Molnar Precision LTD manufactured Commando crankcases.  Please know that our Oil Union Junction Block will fit pre-Norton Commandos such as Dominator and Atlas models. However, that will require some slight adjusting to fit, to include replacing the retaining stud and sleeve nut with a 5/16 Whit allen bolt. Direct-Connect your stainless steel lines from our Union Block to our Billet Oil Filter Kit as I will be doing on my Norton 920 cc JPN. Address any questions to



In addition to our product portfolio for TT and other Ducati racers, we are also excited to support enthusiasts for Norton Manx and Norton Commando racers through Molnar Manx and BritIron Classics Norton. Check out our Norvil fairings & windscreen offerings. Please review the numerous newly manufactured TTDucati F1 and Norton Commando items such as our aluminum fuel tanks, for example, and listed on my website. British marques are listed on the Britiron or Manx section of the website. As a result of our offerings, it is our hope to help you to become immersed in the history, the passion and the early technology of these amazing machines. Let us "Fuel Your Race Passions" to keep the sport of Vintage Motorcycle Racing alive and well!!


Share this post

← Older Post Newer Post →

Leave a comment

Please note, comments must be approved before they are published.