couple more simple mod questions

[phatmanace]

folks,

I have a 1990 uk 1.6 '5 - quick question about a couple of potential mods I was considering

- can I fit an LSD?
- can I fit a 6 speed box?

any idea how much either of these things would cost? [happy to consider recon'd]

Cheers
-Ace

[slinky]

you probably already have an LSD, however, it will be the Viscous LSD that is widely regarded as being dead after 60k...

You can fit the Torsen diff, typically fitted to 1.8's.. To do this you will need the propshaft, diff and half shafts...

Cost for that depends on who's doing the work and whether you can find a diff and associated parts nice and cheap..

6 Speed box, I'm not sure, I'll have a look somewhere for you..

slinky

[slinky]

6 speed box is a yup!

Have a look at miata.net/garage (a site that should already be in your bookmarks!!)

slinky

[mx-5 lazza]

While you can fit a 6-speed gearbox I wouldn't bother. The 5-speed is much nicer and has a much more positive gearchange.
With the 6-speed it's easy to get "lost", especially when coming down through the gears in a hurry (like when you're approaching a hairpin on the track).
The ratios on the 5-speed are fine if you're pushing hard. The only disadvantage is the relatively short final drive (combination of 5-speed + dif) making motorway driving a noisy affair.

[phatmanace]

thanks for your replies folks,

does anybody have any idea of cost for these mods?

I was thinking about £500 each - for recon'd bits. Does that sound reasonable?

-ace

[slinky]

Sounds good to me chap..

[mx-5 lazza]

What's your reason for wanting a 6-speed gearbox?

[anonymous-user]

The six speed is essentially a close ratio 'box with 6th being a roughly similar ratio to 5th in the 5 speeder. The difference in overall gearing comes from the diff. These are available in 4.3:1, 4.1:1, 3.9:1 and 3.6:1.

If you find a 3.6:1 Torsen (from a Mk2.5 Sport) and you're not after such a tall diff, let me know please!

By the way (might be shooting myself in the foot here...) I worked out the ratios a little while back (unfortunately I appear to have deleted the Excel), and found out that the overall ration of 5th in the 6 speed + 3.6:1 diff is almost identical to the ration of 5th in the 5 speed + 4.3:1 diff on early cars, so the tall diff combined with a 'box change gives you an "overdrive" type top.

[mx-5 lazza]

I thought it was 4th that was the same ratio with 5th being slightly shorter and 6th being slightly longer in the 6-speed.

The point I was making though is that the 6-speed box isn't an improvement over the 5-speed (the gear-change on the 5-speed is much better) unless you are changing the diff at the same time to make for more refined motorway driving. Simply slotting in a 6-speed in place of a 5-speed will make the car feel a bit peppier but will probably actually make it slower due to the increased number of gear-changes required. better to stick with the 5-speed and go for the redline before changing gear

If you are going for FI it's a different matter. The 6-speed is a stronger gearbox and can handle bigger torque than the 5-speed though we are talking big numbers to break a 5-speed.