88 GG JB 392
4 A SF20 Z282

Been trying to find out what diff this is all night!
Some of the numbers could be wrong as very corroded tag!

PLEASE HELP ME!

3.92 ratio
open (not LSD)

are you sure? How can you tell?

quote:

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Originally posted by matt.c
88 GG JB 392
4 A SF20 Z282

Been trying to find out what diff this is all night!
Some of the numbers could be wrong as very corroded tag!

PLEASE HELP ME!

---

The ratio is written in the top right hand corner of the tag.

right, on the diff i have fitted to the car it has no tag. So i marked the top of the input shaft and marked one of the driveshaft ends. Turned the input shaft untill the driveshaft returned to the top position and it turned 3 times plus it ended up at about 8 o clock position, what sort of ratio does it have(Not LSD)?

It could be a 3.62 then as that would take you near to 8 o'clock after the 3 full turns. Is it push shafts of Lobro ones?

the main ratio's are 3.6 ish or 3.92.

so its one of those!

)

(you can also get 3.3 and 3.1 but they are VERY VERY rare, actually, no rarer than that!

bolt on shafts, so could be a 3.62?

Is that good for a BEC ZX9? Top speed?

It could be a 3.62. A 3.14 is the best. Top speed depends on your wheel size and tyre choice too.

Look for the bike calc on here.

O

thanks all

This is the calc you need:

LINK

Do you know what the gear ratios are for your engine? What year is it? What RPM does the Rev limiter kick in at?

What wheel and tyre size are you going for?

Using this calc I found that running a 3.58 diff with 13" wheels and 205/60R13's on the rear I could achieve 129 MPH (in
theory) lol.

I could get 145+ with a 3.14 diff but they are as rare as hens teeth and there is no way a Locost 7 can aerodynamically achieve that.

HTH

O

Hi Matt,

The ZX9 is one of the lower geared bike engines and as such you will need a lower ratio diff than 3.62 ideally. A 3.62 with 205/60R13 tyres will give you 112mph at 11,500 revs. You will easily run out of revs on a trackday and that will be very frustrating.

A 3.38 diff will get you to 120mph - much better, if still a little short. If you go 205/50 R15 tyres this will get you to 122mph. Don't think of using 17" tyres (please).

Hope that helps

Paul

The only way of knowing what ratio it is with no tag is to take the back plate off and the ratio is stamped on the crown wheel.

A good tip to find out if its LSD is to lock one of the wheels off, then turn the free wheel, if its lsd it will lock aswell, if its not lsd it will spin very easy

Mike