I know I`ve not even driven my car with the Mx3 gearbox yet , but I`ve spotted a 6 speed `box on fleabay - can anyone work out weather it would be worth swapping , or are the 6 gears just closer together (with the same first and top ?)

Is it an MX5 box?

Depends on the box.

some have an ultra high top gear.
Some have sixth geared the same as fifth is normally with 5 close gears.
Caterham 6 speed has 6th as a 1:1 straight through gear same as most 4th gears. Every other gear is stacked close under it.

Anymore than 5 speeds for a road going engine is superfluous IMHO.

Thats fantastic - thanks
If I`d hung on the 4.1 diff that was in there I would definatly go for the 6 speed , but I`m not sure its worth the work and expense with a 3.9 .

Mazda obviously thought it was worth it in the MX5...

6 speed in the Anniversary Edition had a 3.9 instead of 4.1...

i'd disagree about the 6 gear comment - i've got 6 and its a) fun and b) practicle having the 6th gear (its slightly higher ratio than 5th on the standard cars).

My Seat Leon Cupra had 6 gear, fun to.......

Am I missing something? How does constantly swapping cogs=fun? BTW Porsche thought 4 gears were more than adequate for the 911 turbo!

My Espace has 6 too.

I can only see lots of gears being beneficial in cars with short power bands - ie diesel, but they also need to be sequential, for quick changes.

Strangely enough, Mercedes agree with me, and use 7 speed autos in their diesels

My ZT260 had 5 and that was fine. Deimos with the 3.92 diff has 4 - 2 to 5

ATB

Simon

I think it will depend alot on how much torque you have as to weather you need a 6th gear.. I know on my tin top I keep going to shift up at around 70 mph but there is not another gear, just to drop the rpms down another 500 would be nice. My locost is setup to be run-eventually in mostly 2,3 if being very naughty as that will keep me in the torque range from 15 mph to way above anything legal in Canada. But I will also be in the range of 250-300 foot pounds torque. 4th and 5th for easy crusing.
Dale

My view is that the 5-speed is sweeter shifting but avoild the really early version as it has a single syncro between first and second.

What got me thinking about the 6 speed is - I used to run a type 9 on my crossflow , with a 3.9 diff 5th was too high . So I fitted a 4.1 , 1st became allmost useless but it was so much better everywhere else .
I`m just pondering - with a lower revving V6 and a 3.9 , maybe the 6 speed would be a good move , or will I have to track down another 4.1 to get it right ?
Any body know the standard ratio`s in a type 9 ?

3.65
1.97
1.37
1.0
0.82

PS Just hurry up and get the bugger on the road....

Claire,

Which V6 are you using - is it an old Ford lump or the Mazda unit.

I'd be inclined to stick with the 5 speed box and go lower still will the diff ratio - to about 3.2.

Deimos (Rover V8) has Sierra 3.92 diff and 1st (and sometimes, 2nd) are useless.

I was going to go for 2.88:1, but now have a 2.28 unit, which should give me longer gears and makes 1st useful.

With the Sierra (3.92) diff, 1st gear does 5.24 mph per 1000 rpm (so 30 at red line), with the new diff 9mph per 1000 rpm (and 50mph at redline) same as using 2nd with old diff.

It also means at 70 mph in top my revs will halve from 3500 to 1750 so fuel consumption should go down dramatically too.

HTH

ATB

Simon