I have a diff centre I got from the wreckers out of a 120Y that I assumed was an H150, but in looking for a new crownwheel and pinion to fit it I came across a set but its for an H150A. How do I know if my diff is an H150 or an H150A, or an H150B?

And if its not an H150A, which Australian delivered car does have this diff?

Also will my Nismo H150 LSD bolt into an H150A?

I have three build plates in front of me, all from B310 wagons.
One is a WHB310 & it came with a diff that was coded HA38. I think that the 'H' in WHB310 means the A14 engine as this is what it had while the HA38 is a H150 differential in 3.889 to 1 [3.9] ratio.

The other two plates are from WPB310's with HB37 diff codes. I think that the 'P' in this case is for the A15 that they both had & the diffs were H150b in 3.7 to 1 ratio

HA= H150
HB= H150b as best as I can tell.
Since the H150 series diff that you have is from the earlier 120Y & is in 3.9 to 1 ratio, I would guess it is an H150[a?]

Feral seemed to think that the H150b used a lower mounted pinion, which meant that the gear teeth would be at a different angle, but in the H145 & H165 the 'B' version of the diff meant a switch away from the fixed length sleve & shim method of pinion preload adjustment to the collapsible sleve method.
I do not know if this applies to the H150, but for diffs that take a fair floggin', I prefer the earlier method as there have been instances where the collapsible sleve has been known to collapse just a little bit more, resulting in a pinion that could move & ultimately, a noisy diff, with all the bad things that result from such things.

I think I need to talk to you about that differential, ..... soon.

that 2000 sports in your pic is that your and is it a 1600 or a 2000? (i hav a 68 sr311)

Yes, it depends on the ratio you currently have.

H150B only works with a few ratios. For all other ratios, you need a carrier (pumpkin, third member) of the other type.

See Rear Axle Swaps, H150

The Wiki says,

H150
The Hitachi H150 was fitted to B210s and B310s with A14 and A15 engine. It can cope with more torque than the smaller H145.
Ratios from Nissan North America:
1975-1979 4sp and auto: 3.889
1975-1979 5sp: 3.70
B310 1980: 3.889 (Auto & all A12A)
B310 1980: 3.70 (A14 manual)
B310 1980: 3.545 (A15 manual)
Datsun Competition (later Nismo) used to sell various ratios: 3.545, 3.7, 3.9, 4.111.
For 1980 and newer vehicles, look at the engine compartment build plate. It will list whether you have an H150B (HB) or regular H150.
HA38 - 3.889 ratio
HB37 - 3.700 ratio

Which doesnt seem to mention the H150A

Am I right thinking there are three H150's a standard an A and a B?

or is the standard also known as the A?

The car in the avatar is my 69 2000.

Edit
Previous rubbish deleted.

This is a link to a previous thread that covered this subject with comments from a well informed source. [not me]

hi guys.. can anyone advice me on the pinion bearing preload? for new bearings. also pls advice for old bearings.

The bearing preload specifications are for use with a new crush tube.

See Differential Service

many thanks..
this really helps alot