21 replies to this topic

[mini.rich]

Hi, just got a quick question, are they really worth it?? I'm in the 'research' stages of a 16v build for my MPi and i'm considering a 5 speed box as it will be used daily on motorways.
My 4 speed is ok, but i have a 3.1 FD at the moment and to be honest i prefered the 2.7FD because of the lower cruising revs, but accelerates better with the 3.1. If i use a 3.1 it will be something like a 2.7FD in the five speed(depending on which i go for)

Really just want to know people's opinions/experiances of them.

Cheers Richard

[mini7boy]

if you decide to go with a 5-speed, make sure you buy the right brand. There are still some Jack Knight used units floating around even though Jack Knight may or may not even be in business.
If it isn't already the case, it may become difficult or impossible to obtain repair parts if it becomes necessary. Plus, resale might become very difficult. Something to think about.

False economy is no economy. Be a smart shopper.

[GraemeC]

The majority, if not all, 5 speed bpxes use a 1:1 top gear the same as a 4 speed. So cruising will be no different with the smae diff in each.

What a 5 speed may do is give you better acceleration with a 2.7 diff.

But with a 16V MPi I would expect it to pull away smartish even with a 2.7 diff!

[mini.rich]

if you decide to go with a 5-speed, make sure you buy the right brand. There are still some Jack Knight used units floating around even though Jack Knight may or may not even be in business.
If it isn't already the case, it may become difficult or impossible to obtain repair parts if it becomes necessary. Plus, resale might become very difficult. Something to think about.

False economy is no economy. Be a smart shopper.

Funnily enough, it is a JKD box i have been offered, are these the better ones to go for? thats my point tho, parts etc, i dont want to end up with an expensive box of crap should it die.

The majority, if not all, 5 speed bpxes use a 1:1 top gear the same as a 4 speed. So cruising will be no different with the smae diff in each.

What a 5 speed may do is give you better acceleration with a 2.7 diff.

But with a 16V MPi I would expect it to pull away smartish even with a 2.7 diff!

I was under the impression 5th acted like an overdrive? otherwise it would just be a close ratio box with an extra gear and accelerating would effectively take longer because of more gearchanges. I was reading on minispares their 5 speed evolution box gives a 3.44 CW+P a 3.037FD or something like that in 5th.

Thanks

[GraemeC]

Apologies - looks like the MinSpares one is an overdriven fifth. Check the JK though - I don't think that ons is.

Parts for JK boxes can be hard to get hold of.

[mini.rich]

Apologies - looks like the MinSpares one is an overdriven fifth. Check the JK though - I don't think that ons is.

Parts for JK boxes can be hard to get hold of.

What about the John Cooper Works ones? as there is one on the bay now.

Is there anywhere with info on different types of five speed box'es??

Ta

[Bungle]

i would of thought if you are building a 16V engine you will end up with too much power for a 5 speed box

on the advice of my engine builder i had to restrict the diff used and the power of my engine to suit my JKD 5 speed box

[GraemeC]

Plugging figures into Guessworks website shows neither the JKD or KAD 5 speed kits are overdriven 5th whereas the MiniSpares one shows up it is.

I believe the JCW kits were supplied by JKD.

[syholl]

My Cooper S had a 5 speed Jack Knight Box.

I wouldn't recommend one, mine was fitted from new, and i broke it 3 times within 30,000 miles. The first was under warranty, the second cost me £1500, the third i was quoted £4500, as it took the engine out with it. So i stuck a VTEC engine in it instead....!!!

Stick with the 4 speed.

Sy

[mini.rich]

i would of thought if you are building a 16V engine you will end up with too much power for a 5 speed box

on the advice of my engine builder i had to restrict the diff used and the power of my engine to suit my JKD 5 speed box

How can i end up with too much power for a five speed box?? if 5th is a 1:1 maybe, but i can't see how if it is overdriven. And if it is a 1:1 in 5th i'm not really interested in it as it seems a bit pointless for a road car.

What did you have to restrict the diff to? and what was your power? Did you have to do that so it didn't destroy the box?

Plugging figures into Guessworks website shows neither the JKD or KAD 5 speed kits are overdriven 5th whereas the MiniSpares one shows up it is.

I believe the JCW kits were supplied by JKD.

Mmm, i think i read somewhere that the JCW kits were supplied by JKD.

Ta

[Sprocket]

All five speed Mini gearboxes, excluding the KAD straight cut dog box, are over driven. There lies the problem. Fourth gear is still 1:1, fitting a 2.7:1 final drive would surely kill the box much sooner. The boxes are weaker by nature of their construction of the fith gear, and, with it being over driven. They would be fine for a near standard 1275 with a decent ratio final drive, but certainly not the 2.7:1, and the 100bhp+ with up to and over 100lbft torque you will expect with a 16v, you need something better, not worse.

I seriously suggest you rethink how you want to use this 16v engine, as they rev to 8000rpm with ease, and come on cam at around 4000rpm. Im not saying they are crap below 4000rpm, just that they come alive after 4k. A 2.7:1 FD you will find it doesnt like 30mph crusing in fourth, never mind a fith gear. Best person to speak to would be Brumski, as he runs the 2.7:1 FD and has recently been concidering changing it out after the Lakes run and Hard Knock Pass.

You wont go far wrong with a KAD fivespeed straight cut dog box, but it is not quiet, or forgiving.

[Sprocket]

The majority, if not all, 5 speed bpxes use a 1:1 top gear the same as a 4 speed. So cruising will be no different with the smae diff in each.

What a 5 speed may do is give you better acceleration with a 2.7 diff.

But with a 16V MPi I would expect it to pull away smartish even with a 2.7 diff!

The only true 1:1 five speed gear box for the Mini is the KAD five speed straight cut dog box

[Nightrain]

The only true 1:1 five speed gear box for the Mini is the KAD five speed straight cut dog box

Your forgetting the 'Collette Francis' box from the late sixties, is this is what the KAD box is based on ? Basically they slimmed down all the components and weren't to reliable because of this.

[mini.rich]

All five speed Mini gearboxes, excluding the KAD straight cut dog box, are over driven. There lies the problem. Fourth gear is still 1:1, fitting a 2.7:1 final drive would surely kill the box much sooner. The boxes are weaker by nature of their construction of the fith gear, and, with it being over driven. They would be fine for a near standard 1275 with a decent ratio final drive, but certainly not the 2.7:1, and the 100bhp+ with up to and over 100lbft torque you will expect with a 16v, you need something better, not worse.

I seriously suggest you rethink how you want to use this 16v engine, as they rev to 8000rpm with ease, and come on cam at around 4000rpm. Im not saying they are crap below 4000rpm, just that they come alive after 4k. A 2.7:1 FD you will find it doesnt like 30mph crusing in fourth, never mind a fith gear. Best person to speak to would be Brumski, as he runs the 2.7:1 FD and has recently been concidering changing it out after the Lakes run and Hard Knock Pass.

You wont go far wrong with a KAD fivespeed straight cut dog box, but it is not quiet, or forgiving.

I didn't say i wanted to use a 2.7 FD, I was planning on a 3.1. I had a 2.7 and i know how it behaves. to be honest, it sounds like a 5 speed is going to give me headaches, so i think i'll stick with a 4.
I'll ask on the EFi forum, as people will have more experiance with the 16v.

Cheers for the help.

[Trog]

I have one of the original "Trans X" Minispares 5 speed boxes which I bought 15 odd years ago... Been off the road for a few years but when I lifted the engine a few months back and checked the box it was still perfect!

Here are my thoughts etc:

Yes it's an over drive 5th, so if you keep the original diff you get an extra cruising gear. This is what I used it for. I was living in Manchester and my girlfriend was in Bath so I did a lot of Motorway drives. I found I used 1 to 4 for A roads and enjoying myself and 5th for the longer cruises... Well worth it in my opinion, to save my ears and cut down the drive time, I could cruise at 80 without permenant ear damage...

Strength wise I would say the whole box is stronger than a 4 speed. However if you are putting over 100 BHP in to it the issue will be the gears themselves (Usually 2nd) so no difference between a 4 and 5 speed there... Untill you go straight cut.

When I bought mine I did a lot of reasearch, at that time Minisport did a box too, The Jack Knight was I thought a little better engineered (Used a unique casing rather than modified Rover) but I had 2 issues with it, firstly cost and secondly it was not owner servicable, any faults and it had to go back... Very expensive. The Minispares one at the time was a kit so I built it up myself and can therefore service when needed...

Only problem I have had with it is a First motion shaft bearing failure which was nothing to do with it being 5 speed but me letting the oil get too hot... But easily fixed (Changed all bearings to be safe...)

In conclusion it's a lot of money, if you want an A series engine and you have the cash it is worth it... For my money go Minispares as they have a good reputation so you should be able to get spares in the future, they have also been making the same box for 15 odd years.