[Robert McDermott]

Lewis,

I don’t think that it is a good idea to fit any other gearbox to your HRG, in particular a box of modern non-British make. It is not in the “spirit” of the whole concept of an historic sports car.
Furthermore, a Bristol gearbox properly set up can be an absolute delight.
I have been building special Bristol gearboxes all my life. I have in recent times created a separate division of my restoration business specializing in developing the Bristol gearbox, and I can produce you any ratio that you desire. I am only too willing to give you advice as to what you need. Below is a copy of an article that I wrote in the Bristol Owners Club Newsletter earlier this year titled “The Bristol Gearbox Cure” which explains some of the story.
For your information, it sounds like you have a Type 400/85A gearbox which, with a 3.9 diff and 600x16 tyres will give speeds at 5,000 RPM of approx. 23, 46, 77 and 100 MPH.
The standard Bristol sports/racing gearbox, CR3 – BWCR6, 9 and 12 will give speeds of 34, 55, 77 and 100 MPH.
The Derek Hughes’ overdrive is a very good conversion without altering the chassis, and will fit exactly where the standard Bristol gearbox will fit. There are several ratios from which to choose.

THE BRISTOL GEARBOX CURE ARTICLE:
For more than 50 years I have been involved in the restoration of specialist and collectable cars. One of my favorite marques is the 2 litre Bristol and its derivatives. I have been working on and developing their components for more than 45 years, and now provide a service which is of great interest to many Bristol owners. The rebuilding of Bristol gearboxes.
The First Gearboxes – Bristol Type Synchromesh
One of the few disappointing features of the 400, early 401’s and 402’s is their gearbox.
Marginal when new, most now have no effective synchronization on second gear, and have very slow synchromesh action on third and top. Many cars now drop out of third gear on overrun, and some have even worse problems. The introduction of the Borg-Warner synchromesh system and a change of ratio on later cars made an enormous improvement.

I have developed and manufactured the necessary components to convert and rebuild the early Bristol gearbox to the Borg-Warner system. The free wheel can also be replaced with synchromesh on first gear if required, and the ratio can also be altered for a much closer and more drivable combination. These modifications will totally transform the way your car changes gear, accelerates through the gears, and handles traffic conditions generally.

If you would like your beloved 400 and 401 to change gears like a 405, or better, and still retain its original gearbox, then this is the solution. By the way, the fitting of a remote control mechanism does not make a Bristol type gearbox into a Borg-Warner type. The improved qualities of the later cars come purely from the internal components of the gearbox.

The gearboxes that are relevant to this Borg-Warner style development are: 400/85A, 400/85C, CR2 & CR3 types. The CR3 type gearbox was only used on sports and racing cars such as the Frazer Nash. This gearbox does not have a free wheel and its ratios do not require alteration. Apart from the first gear synchromesh, the parts used in these modifications are identical to, and interchangeable with the original Borg-Warner style components used in the later gearbox.

The Borg-Warner Type Gearboxes
The later Bristol gearbox built with Borg-Warner style synchromesh, although excellent when new, is now about 60 years old, and many high mileage cars, alas suffer from slow synchromesh and gear drop-out. Simply rebuilding these gearboxes with new bearings and synchro rings will not necessarily restore their superb original drivability and feel, and will not cure gearbox drop out for more than a very few kilometres.

As with the early “Bristol” type gearbox, the cars fitted with the BWCR5, 7 & 11 gearbox can be further and greatly improved with a change to first gear ratio. These gearboxes are fitted as standard to the 401 from Chassis 1006, and 403, 404 and 405 cars. The inclusion of synchromesh on first gear is far more robust than the free wheel, and also provides the driver with a much more useful facility in traffic and it’s also a lot more fun. Gearbox types BWCR6, 9 & 12 are used for racing and sports cars such as Cooper Bristols, Arnolt and AC cars. The ratios are the same as CR3 and without a free wheel. However synchromesh on first will make all of these cars easier to drive and faster in gymkhana events. The CR3, 6, 9, or 12 are not suitable for the saloon cars with the standard 3.9 differential.

I have in stock all the components to correctly overhaul the Borg-Warner type gearbox to ‘as new’ condition, and if desired, to carry out the modifications. For those who are interested in enjoying driving their Bristols, you won’t be disappointed. If you are having gearbox problems, I am happy to speak with you. My phone number is: 03 9362 0291 or (m) 0416 074 120.

Robert McDermott.