5 Speed gearbox

[mgdmurray]

Has anyone in the club fitted a Type 9 5 speed gearbox (Ford) to a Bristol 406 or similar 6 cylinder car?
Original overdrive gearboxs can be a bit pricey and I was thinking of an alternative more economical box.
Any advice is appreciated.
If you wanted to change the front drum brakes on a 405 for discs, what type of axle/ hubs would be required? From what vehicle. Again, any advise is appreciated. M

[Geoff Dowdle]

Mike,
I have fitted front disc brakes to both of my type 400 but have used 405 hubs & 406 discs, one with Girling #17 calipers ( ex from memory a Humber of the late 50's- early 60's) . The other 400 I fitted Coopercraft alloy 4 piston calipers with a larger pad.

What disc (non ventilated) you can use is from the front of a 5 series BMW c1992. This will need some machining of the ID and a new set of bolt holes as the PCD is not the same as the Bristol hub .(I have been told a MBenz disc will also fit but are smaller in OA diamenter ). The offset of this BMW disc gives enough clearance for probably many calipers , when the disc is bolted on the 405 hub in the position of the original drum. When the disc if fitted you will then have to do a trial fit of your selected Caliper to see that the caliper does not touch the wheel rim .
Then you will have to fabricate a steel caliper carrier to mount on to the stub axle where the drum brake backing plate originally is fitted. The caliper carrier will need spacers of the correct thickness made and welded to it , to space the caliper accurately to the disc.
New flexible brake hoses will need to be fitted.
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When all of that has been completed the master cylinder front valve will need removing or made inoperative .
The rear brake drum cylinders (1.125inch dia) will need to be replaced with 7/8 inch diameter cylinders , or the rear drums will lock when the brakes are applied. An alternative is to fit an adjustable pressure valve in the the brake line to the rear drums while using the original 1.125 cylinders.

I also upgraded the drum brake servo to higher pressure unit and fitted a vacuum tank as per 406 and many Jaguar of the 60's .

I seriously recommend you get further advice from a Brake specialist or mechanical engineer before you contemplate this conversion.

The original 12 inch 405 drums when in good working condition actually stop the car quite well.

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Regarding fitting a type 9 Ford gearbox to a Bristol, I have done this conversion . It was quite a project . I used a Type 9 from a 2.8 litre Ford Capri , it had the best set of gear ratios for a Bristol but more importantly the input shaft is longer and necessary if you plan to use a Bristol bell housing with an adapter between bellhousing and Type 9 . I purchased this Type 9 from a small Ford dealer who reputeable had it reconditioned.
The Bristol clutch plate needed replacing as the splines of the Type 9 are finer than the Bristol .
I had to have a new drive shaft to the diff made .
Gearbox tunnel , speedo cable , gearbox mounts all had to be made as well .

I have found after using this gearbox for about 10 years, but only over about 4000 miles I rarely use the 5th gear except on a freeway above 70 mph .
The gear spacings are ideal but overall this gearbox is not as nice to use as a BW CR11 fitted to a 405 and 406 . In the future I plan to remove it and fit a BW Bristol box . But saying that a 400- 404 has a 3.9 diff ratio originally fitted, compared to the lower ratio in a 405 at 4.22 that originally had an O/D, so you will probably need a 5 speed or O/D gearbox .

Do your research before you start on either of these conversions

Geoff