$50 - 3.7 is really common here

Shipping to AUS might be as cheap as $55 USD. Depends on the dimensions of box needed.

Well Ive put my hand up in the past for a 3.545.
I might have a 3.7 to try out soon to replace the 3.9 in it
at the moment with Chris's spacer plate and Im pretty sure
it will improve things at 100km/h but not by much.

The 3.545 will be ideal with the 3sp auto 1:1 final drive
and 165/70/13 inch tires powered by the a12 but an A14/15
will definitely need a 3.5 at minimum in featherweight Ks.

i seriously think this obsession with lower numbered diff ratios is going to leave you with a really sluggish car. I used to get awesome fuel economy with my a14 when it was carb with 165 65 13's and a 4.3, at 100 it did rev high but seemed to chug along fine. i since changed to a 3.9 and while it helped keep the revs down to a nice level at 100 it certainly lost poke. It didn't matter too much with the injection and exhaust and cam being able to cover it up but with a more standard setup i think it would be a step backwards.

worth a try but you'll have a much slower car around town

I guess it depends how much you drive at highway speeds....or where you cruise.

I haven't had any other ratio other than what I'm running so I'd be interested to see how it all differs.

I rarely go near 100 so I'm cool with the current setup. But just curious abut what other ratios will offer.

Chris

check this link out guys

driveline calc

handy for seeing the effects that different ratios will have

i worked out that with my gearbox/diff/tyres
if i can get my ute to spin to 10,000rpm in 5th.. ill be doing 300km/h

so my car when it hit rev limiter(6000rpm i think) in 5th it was 204kph and with the new box limiter in 5th will be 234 kph
and if the rev limit it lifted to 7000 it should be good for 273 kph

well thats handy to know, also with the new .75:1 5th instead of the .86:1 means that i can run 4.11 instead of 3.7 and still have a higher top speed

10000rpm if 5th, i thought victas went out to 15000rpm f1 style? ;)

Lags the issue with yours losing poke could have been the camshaft?.
The a12 I have is slightly higher comp and churns well at all speeds
and overtakes with ease 100kmh and over.

It actually runs out of first too quickly so I know with a 3.7 it should
be a little better. A 3.54 will be the beez neez and its no obsession
just prefer using the torque rather than hp around town not to mention
hating first gear and almost able to take off in 2nd comfortably.

I remember the a15 in my coupe with 79mm bores been a real stump puller
with mild cam but useless without a 5 speed & 1st might as well not exist.
The stock camshaft made it even worse with all torque.

Using the calc with 165/70/13 and 1:1 final at 100kmh the 3.9 is at 3700rpm
no wonder I wasnt happy with the noise!!! With 3.7 this drops to 3500rpm so
will need an overdrive if using an A12

a10 piston velocity at 7000rpm redline is 826.000 m/min 3500rpm is 413m/min
a12 '' '' '' '' 980.000 m/min '' '' 490m/min
a14 '' '' '' '' 1078.000 m/min '' '' 539m/min
a15 '' '' '' '' 1148.000 m/min '' '' 574m/min

So with 3.7 rear at 1:1 and A10 piston travels
77 metres less than A12,
126 metres less than a14
161 metres less than an A15
to cruise at 100km/h

All changes with a rare overdrive 5 speed.

I guess it all depends on where ones priorities lie.

For me, ... well I couldn't really give a rats rectal orifice about dazzling acceleration, & I do not much like seeing the tach pegged on 3,500 rpm [or more] at a paltry 62mph [100 kph]
It makes too much noise & wears the engine too quickly.
Bugger that for a joke.

For my street hack I would prefer to use the A15 [which I have] plus the tallest diff & tallest tyres that are practical.
The torque of the A15 with GX induction & a mild cam will still provide far more than adequate performance in urbane areas & the tall gearing will keep me percolating along a highway speeds while my car behaves like the clever Datsun engineers intended as it sip sip sips the fuel.
It's a good feeling when you pull up to the pump after a 350 mile [530k] drive with a 7.7 imp gallon [35L] tank & fill 'er up for change out of $40. [at todays prices.]

I would split my mileage up as less than 10% urbane driving & over 90% Highway cruise.
It's horses for courses.

This is the dilemma and the reason everyone with an A series wanting/needing an overdrive box.
No one wants cruising over 3500rpm especially so with an a15, to think 3700 rpm drives me crazy
with an a12 Id rather cruise at 2500rpm where I know this stock and torquey a12 loves to be.