For sedan and coupes:

As far as im aware there is no other ratio that can be simply swapped into a standard (H145) diff and youre stuck with the stock 3.9:1

 

For utes:

See H165 ute diff conversion

 

If youve got a ute already youre lucky in the diff department, the ute diff has bigger housing, fatter axles and is considerably stronger with many ratios avaliable.

 

To put this in your sedan or coupe:

It will practically go straight in depending on what you got when you got the diff (they are getting extremely rare so you cant be fussy) mine came with nothing and i actually had to reweld mounts back to the housing as they'ed been taken for a commodore diff conversion. I found the u-bolts and bump stops from H145 were too small and i had to get the u-bolts from a vanette but use the shocker mount plate from the H-145 by elongating the holes as the vanette one had a diffrent pin size for the shock to mount to, I havent got bump stops yet but im guessing blubird ones will work though i havent seem them yet. The standard brake lines will match up with a little bending (by hand is fine) and using something to clamp the splitter in the brake line where in heads off to either brake to the diff housing is a good idea as there is no bolt hole like the H-145, I guess the tailshaft from the ute is the same as the ute has the same wheelbase but as i didnt get one i had one made up, that cost $200 but the guy machined out the uni joint housings to accept replacebale ones and also put a larger stronger uni-joint in the front (the standard front one is quite small and apparently weak) just as a precaution.

 

There is some option with brakes but thats under the brake directory.

 

Ratios avaliable include:

3.9:1      from some bluebirds with H165 diff

4.11:1    from 1200 Ute and a-15 vanette

4.875     from a-12 vanette

5.1:1      I've heard is available, any idea anyone???

 

There was i think 500 bluebirds built as government vehicles, these had lsd's in them but good luck finding one, they had no special markings to help you either

 

This diff is bigger again in housing and axle size ect. and will bolt in similar to a H-165 except you must have the spring mounts moved, problem here though it has a wider track than the H-145 and 160's by about 90mm this can be overcome in two ways, first is to use fwd offset rims on the rear of the car (which means diffrent wheels front to back on car) or by flaring the guards which is legal accept in rallying (in AUS) but will cost a few hundred bucks to do. Mind you flared guards looks pretty sexy.

 

These would provide the ultimate in strength, but require some work to fit including cutting down in length and are not cheap to install, you need to talk to a diff guy to see whats involved in this.

 

you do get a good choice of brakes with these diffs but they will weigh a fair bit more than your datsun diff too, I would only bother for a car with extreme power and a driver that likes the smell of burning rubber.

 

Other diffs I've heard of being used include Hi-lux (come with lsd) and also mitsubishi scorpion diffs, these require a fair dit of modification to fit also as all the suspension mounts and stuff have to be removed and replaced with the 1200 ones, these diffs are also diffrent wheelbase to 1200 but they each pose there own benefits (brakes, ratios, lsd's etc.)

 

The diff is modified so that two plates are fitted into the diff centre with springs applying equal pressure on either axle, proving a break away pressue of appox 50 psi (lsd is about 75-85psi i think and standard open diffs are about 20-25 psi) so its a midway thing, but it only costs $250 to get fitted and has proven to last 3 rally seasons quite regularly, when it does die the diff acts open centre and costs $150 to make like brand new again, the guy that did it for me takes youre diff centre for approx. 10 days so you need alternate for mean time. the only restrictions as far as the car goes is that it will fit all diffs except 2 he found he couldn't do so far (i think charade and some other small thing) so h190 is no prob and other restriction is the car has to have less than 200hp (at wheels i think it is). apparently there are a few guys around doing this conversion but the guy that did it for me is called "Tayell Automotive" in East Bentleigh Melbourne Ph: (03) 9579-5529 and John is the blokes name

As far as driving charachteristics it basically acts like an LSD, as in both wheels will put power to the ground but when turning the outside wheel will be allowed to spin faster and not harm turning or scrub tyres, also im told it will not push you through a corner anything like a locked diff does when youre going hard, though it will a little. This is all what ive deen told as ive only had the
conversion done for a few days i havent fully explored its driving charachteristics though it seems very effective, see project car in october 4th entry for descritoin of what ive found so far.