How to work out what diff ratio you have?

[BlackSupra]

I have bought a complete G series diff, ratio beleived to be 4.1.

Is it as simple as counting up the teeth on the gears to determine the ratio or is there more to it?

Does anyone know or have a table of teeth numbers for toyota diff gears?

[roadsailing]

yeah count the teeth, then apply this formula

gear ratio = numbber of teeth on big gear divided by number of teeth on small gear.

if its in a car you can work it out by RPM vs speed in 4th gear, slightly more complicated but not much.

[slide86]

the way to work out what any ratio between to gears is

DRIVEN/DRIVER.

ie count the teeth on the crown wheel and divide them by the teeth on the pinion. that will give exact ratio!

[BlackSupra]

THanks guys.

[crowncustom]

The ratio should be stamped on the crownwheel eg.39x9 or 39/9 etc.
Cheers Brett.

[oldcorollas]

/\/\/\/\ wot he said toyota crowns should have it stamped.

you can also do it by just rotating the flange, and seeing how many times the axles turn.

ie if you think it is a 4.11 (37/9) rotate the pinion 37 times and see if the axles rotate a full 9 times

if you think it is a 4.1 (41/10) rotate pinion 41 times and see if axles rotate a full 10 times.

a bit of wire wrapped around the bolts and sticking out as a pointer help to make it accurate... as does a second person to do the counting

[Robbos_Toyotas]

take the rear case off and count the number of teeth on the crownwheel. Then count the number of teeth on the input pinion. Divide the crownwheel number by the pinion number and there is your ratio. Thats the ONLY accurate way to do it. Ive been fooled by the rotation way before.

what exactly is it out of? MA70 non turbo auto ran a 4.1
MA70 turbo auto ran a 3.9
MA70 non turbo man ran a 3.9
MA70 turbo man ran a 3.7

Ga70's were all open - 4.5:1, and 4.1:1 from memory

JZA70 man ran a 3.7
JZA70 auto ran a 3.9

99% sure those JZA70 ratios are correct....they are torsen LSD as well

[BlackSupra]

JZA70 but with an aftermarket centre.

[Robbos_Toyotas]

JZA70 but with an aftermarket centre.

I guess means you are gonna have to pull it apart. But i bet its a 3.9 or 3.7...Honestly its the most reliable and sure way of finding out instead of sitting there rotating it and confusing yourself.

[BlackSupra]

Yeah, its going into my soarer which has 'who knows what' diff in it, was auto, now manual and came from factory as open centre.

So i guess it's pull them both out and look at the crownwheels to determine which one to use.

[oldcorollas]

I guess means you are gonna have to pull it apart. But i bet its a 3.9 or 3.7...Honestly its the most reliable and sure way of finding out instead of sitting there rotating it and confusing yourself.

but... some people can count without getting confused

[1200det]

Place a mark on the tyre at bottom dead centre. Crawl under the car and place a mark on the driveshaft. You'll be counting how many times the driveshaft turns in this test, so place the mark at a convenient place that you can call "zero".

Have a friend turn the left wheel for 20 rotations. Have them count to themselves while you count driveshaft rotations. When they are completed, divide the number of driveshaft revolutions by 10. For instance, 30 turns is a 3.00 differential ratio. 37 and a third turns is a 3.73 ratio. If you know the factory-available ratios, this will put you close enough to quickly determine which ratio you have. If you don't know the factory options, then do a larger number of wheel rotations (say, 100) and divide by 50 for a little more accuracy on that last decimal place.

You're done! You can put the car back on the ground now.



.

[Robbman]

what exactly is it out of? MA70 non turbo auto ran a 4.1
MA70 turbo auto ran a 3.9
MA70 non turbo man ran a 3.9
MA70 turbo man ran a 3.7

Ga70's were all open - 4.5:1, and 4.1:1 from memory

JZA70 man ran a 3.7
JZA70 auto ran a 3.9

99% sure those JZA70 ratios are correct....they are torsen LSD as well

For the States there was no difference if it had manual or auto. I've heard that non-US MA70s had different ratios as well...

Anyway, for the States...

All MA70 non-turbo had 4.30s (clutch or open)
MA70 turbo 87-88 had 3.91 clutch LSD
MA70 turbo 89-92 had 3.73 clutch LSD



Other info...

GA70 non-turbo had F-codes 4.56s (clutch or Torsen)
GA70 turbo had G-code 4.56s, (clutch or Torsen)
JZA70 manuals had a 4.10 Torsen
JZA70 autos had a 3.91 Torsen

[Robbos_Toyotas]

For the States there was no difference if it had manual or auto. I've heard that non-US MA70s had different ratios as well...

Anyway, for the States...

All MA70 non-turbo had 4.30s (clutch or open)
MA70 turbo 87-88 had 3.91 clutch LSD
MA70 turbo 89-92 had 3.73 clutch LSD



Other info...

GA70 non-turbo had F-codes 4.56s (clutch or Torsen)
GA70 turbo had G-code 4.56s, (clutch or Torsen)
JZA70 manuals had a 4.10 Torsen
JZA70 autos had a 3.91 Torsen

bizarre they are totally different to aus!!

[BlackSupra]

Well JZA70's were never sold domestically in Australia or USA.

So someone is wrong.