20 replies to this topic

[DeadSquare]

Even the most basic Ford Ka has a 6 speed box. It's technological advancement. We couldn't keep using the good old powerglide transmissions.

 

Surely they are not still making those 3 speed boxes from the fifties, but fitting two per car ?

[Dusky]

Even the most basic Ford Ka has a 6 speed box. It's technological advancement. We couldn't keep using the good old powerglide transmissions.

Surely they are not still making those 3 speed boxes from the fifties, but fitting two per car ?

They're not fitting 2 per car. And apperantly its usefull. Imagine the massive savings of cutting box material costs roughly in half.

[Bobbins]

Yes, heavier cars that can do much higher speeds than a Mini.
 
The most important thing is to have good ratios to match where your engine makes the power you need to drive at the road speed you do.
 
There's nothing that wrong with a 4 speed Mini that justifies splashing out £2k, at least that's my opinion.

My other "toy" is a 220 bhp Caterham that weighs a couple of hundred kg less than my Mini, it has a 6 speed box but geared low enough that in 6th gear it's doing similar rpm/mph to the Mini, so certainly not high geared and a bit painful sat on the motorway above 75ish ... sound familiar?
It's simply fabulous though and if I could run with 6 close ratio gears in the Mini, even with the same top gear ratio, it would blow the 4 speed into oblivion. The 4 speed was a good step up from 3, but the only thing holding back going for more than 4 is how much you can afford or justify spending. 5 is better than 4, 6 is better than 5. It's just progress.

[Tupers]

More gears won’t make a car cruise better once you’re in top gear it’s all about your final drive ratio.

Modern cars aren’t getting into double digits on gears because “more gears are better” they have them because more gears allow the car to stay at an optimum operating speed for efficiency and emissions.

In a racing situation having a lot of gears with smaller differences between ratios allow the engine to stay close to it optimum speed for power and torque. This saves the engine from bogging down when you’re going up and down the box and makes for faster lap times.

When driving on the road where lap times aren’t important more gears won’t always make the car better it could just give you more work to do on the motorway.

[Ethel]

Fair do's, depends how peaky a cam you're running to a degree, but I'll concede that'll matter less in something as light as a Caterham with 200+hp.

 

The thing with Mini 5 speeds is they're really a 4 speed with an overdrive added. You could stick a shorter final drive on, but they're probably at their most reliable with the direct driven 4th still being the default for spirit driving.

[Nathan1293]

Most mini 5 speed conversions do have an overdrive 5th, but the KAD one doesn’t it is a 1:1 5th gear.

It really depends what you want with respect to overdrive or not. In fact most modern 6speed boxes, 5 and 6th are both overdrive.

I take your point though is it needed, for non-forced induced induction, more gears is better imo, first can be low enough to not be a pain pulling off, other gears are close to it and each other, top gear has a sensible cruise rpm.

I’ve looked into the gearing and you can make any of the current options almost exactly the same with different final drives. Overdrive boxes with a 3.7 give roughly the same as kad 5speed with 3.4 final drive.

Not is it worth the huge costs, probably not. Forced induction means more torque generally lower in rpm range, so a tall final drive works well, as it allows boost to build and good performance, but also good cruising comfort too.