5 speed box
Turbo Mini Forums

Just wanted to get peoples thoughts on a few things I've heard about 5 speed boxes:

1) They can't handle much torque? Is there any reason they would handle less torque than an equivalent 4 speed?
2) No one produces them anymore? (Apart from the KAD race box)
3) Someone on this forum was discussing converting the mini casing to run a modern 5 speed gear set from a Fiesta or something??

Any views much appreciated.

Nick.

Jack Knight do a 5speed to fit the STD case (DOG or SYNC) around £1500 i think.

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

Minispares sell them off the shelf http://minispares.com/Shop.aspx?ccid=1501

Minispares - Is that not just an overdrive and not an extra gear?

Most, except the KAD box are 'overdrive' fifth gear and use the empty section of the casing originaly used for the selector mechanism back in 1959. The lay shaft is a two peice design, and as far as I am aware, this is the problem area and where i have heard of most failures. The KAD is a true 1:1 fith gear and uses the space originaly taken by the four gear set. The lay shaft is a pretty standard design.

Problem with these, is that people tend to accelerate in fifth and the 0.89:1 ratio puts extra stress on the components resulting in premature failure. Add to this a powerful engine and the situation gets worse. A 150bhp turbo motor would rip it to bits in no time.

Personaly if i were looking at five gears, I'd buy the KAD, but then, I'd also need to have won the lottery

Hi,
If the 5th gear on KADs box is 1:1 then that's no different to the standard 4 speed.
To be honest with the broad spread of midrange torque you get from a turbo 4 gears should be plenty. A turbo engine will work well with a tall final drive, which also gives you lower revs on the motorway.
Cheers,
Gavin :)

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Im going to be running a 2.95Fd on my turbo with about 140bhp. This should give me a good cruising speed and not too high revs.

Hi,
I've got a choice of 2.95 or 2.7. Do you think the 2.7 would be too much?
Someone did say they thought this may cause MPi boxes to die early.
Cheers,
Gavin :)

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9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Hi,
Good point about the LSD, don't know if that's what he's going to run .....
Unfortunately according to Sprocket you can't get the overdriven 5th and strength at the same time :(
Cheers,
Gavin :)

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Thanks for the input.

I'm running a 2.9 diff at the moment and the turbo copes fine on the road. It's when you get it on the track you get a bit exposed between the ratios. I've had times when I've caught someone on a track day and struggled to get past as each opportunity I've been waiting for the boost between the big ratio drops.

Following on from Mini Sprocket's info, would an overdriven 5 speed be able to take the torque if you only used the first 4 gears in anger i.e. on the track and 5th as an over drive on the motorway etc? Didn't Vmax Scart have a 4 speed SCCR with overdriven helical 5th gear at one point?

From the Horses Mouth... (Jack Knight)

Thank you for your enquiry, in response:
1. The 5 speed dog boxes were used on the A series engine with a power
output of 200bhp, so providing you have a 'dog box' you should be fine. You will need to check if you have a syncro gearbox or a dog gearbox. If you have a syncro gear box you will need to upgrade to a dog box.
2. Yes we have just release a new 5 speed dog kit for the std gearbox case, which could be a solution if you are using a syncro set in your current gearbox.

Hope the above helps

Kind regards

Nick

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

Fair enough.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Phone the guy at JK and ask.

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

Looking at the stuff they have on the web it's a similar design to the KAD box with a std 1 piece layshaft and direct 5th gear.

Similarly to the KAD box the ratios are very close and suited for racing. The spread of 5 gears is similar to the 4 speed SCCR so no real benefit for cruising.