8 replies to this topic

[Thorpsta]

Hello all,
Recentley me and my dad started restoring his old mk1 mini known as the 'flying flea' for me to use as my first car. Back in the day when it was on the road, it had a standard 4 speed box in it, and dad was always looking for a 5 speed box, unfortunatley he never came across one. After some recent research he fount out that it's the box is the same shape.
What we woud like to know is, is the 5th gear located on the reverse shaft? And can you buy the parts to convert a 4 speed to a 5 speed? If so how much?


Thanks
~Will

[mattw92]

I dont believe 5 gears are needed, I was in my mates 5 speed pug 206 and his revs where basicly at the same as mine doing 70mph even though he had 5 gears and i have 4 on my mini.


So i wouldnt waste to much time on it. if one comes around go for it but dont let it takeover the project.

ide like to say 70mph was done on the motorway where 70 is allowed

Edited by mattw92, 22 December 2011 - 05:28 PM.

[lrostoke]

I dont believe 5 gears are needed, I was in my mates 5 speed pug 206 and his revs where basicly at the same as mine doing 70mph even though he had 5 gears and i have 4 on my mini.

But it depends on the ratios, it could be the ratio on the Pug's 5th gear is the same as your 4th. But not all 5 speed boxes will b the same.

Just checked the specs on minispares for one of theres. The 5th gear gives a final ratio of 2.98

This is the straight cut gear version 5 speed gearbox which has a 5th gear ratio of 0.865 which with a 3.44 diff gives the equivalent of 2.98

So you'll get all the acceleration benefits of the 3.44 diff, but with the top end cruising of a 2.98

as an example on 165/70/10's from Guessworks site

3.44 diff gives 66mph @ 4000 rpm in 4th
2.95 gives 77mph @ 4000 rpm

Edited by lrostoke, 22 December 2011 - 05:43 PM.

[Gulfclubby]

My dad has a JKD 5 speed gearbox and it certainly helps with cruising speed on the motorway. That really is all it does though. If you know already that you won't be driving long distances a lot, I wouldn't bother. I have so far done around 8k miles on my Clubman with a standard gearbox and it was just fine, including motorway driving.

[Bungle]

i don't know how it works but this is what a 5 speed box looks like inside

Edited by Bungle, 22 December 2011 - 06:50 PM.

[colinu]

Yes you can buy parts to convert a 4-speed into a 5-speed (e.g. the KAD kit at £3K which is a true 5-speed as opposed to a 4-speed with overdrive), or spend £2K on a complete unit from Minispares (5th being an overdrive). Personally I wouldn't see any benefit in a 5-speed overdrive box on anything with lower power than a standard 1275cc... I doubt it would have the guts to make any use of the overdrive 5th.

FYI... I own a 5-speed Mini - a John Cooper Sport 5 (JKD helical 5-speed box). It's a 1298cc MPi with some "Cooper magic" sprinkled onto the engine producing 90+ bhp. That level of power make the 5th very usable

[ibrooks]

I dont believe 5 gears are needed, I was in my mates 5 speed pug 206 and his revs where basicly at the same as mine doing 70mph even though he had 5 gears and i have 4 on my mini.

Maybe - but your mate's Pug 206 will be a modern multi-valve engine which makes power much further up the rev range than an A-Series and which is much happier and smoother at those sort of revs.

A far better comparison would be my mate's Moggy Minor which has a Sierra Type-9 gearbox on the end of an A-Series. The first 4 gears don't feel that much different to the original box (although I haven't compared ratios on paper) but on the motorway or dual-carriageway you've got the overdrive to drop into and long distances to shows or for a holiday suddenly becomes practical rather than an endurance trial for both you and the engine.

I'm changing to a different engine and box simply to get a 5th cog because the 5 speed boxes for the transverse A-Series are silly money and in many cases have a reputation for being weak. If I could get a 5-speed box for a Mini for a grand or under that I had any confidence in being able to take 80-100bhp for more than a couple of years then I would stick with my current 1380.

Iain

[Thorpsta]

Thanks for the replys everyone, sorry I couldn't reply quicker

Well, the response is it isn't really worth it, which was my first thought anyway

If one comes up cheap sometime though, I'll get it regardless, I'm just not willing to fork out £2K on one >.>

[phil hill]

i don't know how it works but this is what a 5 speed box looks like inside

That looks like a JKD 5 speed, Helical full syncro.

From left to right : 4th, 3rd, 2nd, 1st (main web) reverse, 5th. The original JKD 5 speed design has a different casing to standard gearboxes, you can see JKD cast into the casing above the usual "CAM" number on the front. I believe the later JKD units used a modified standard casing.

I seem to remember that MiniSpares used to do a kit of parts to convert a 4 to a 5 speed, but I guess they only sell built boxes nowadays.

Probably better just playing with FD ratios to get the best compromise for your engine and duty.

Phil.

Edited by phil hill, 26 December 2011 - 06:49 PM.