NB diff into NA - machining?
 

Is there any machining required for the subframe or chassis?

I have everything set for the swap, just curious..?

D

NB diff and '94-'97 NA diff = 1.8 rear end.

From '94 to '05 they are pretty much all the same, with a few variants in axles(two piece and one piece).

However, it is all compatible with a NA 1.6 Miata. You'll need the differential, housing, drive shaft and axles/half shafts from a 1.8 car.

I think I answered my own question.... Only the very early NA's had the smaller ring gear.

The housings/R&P are all the same from 94-05. The only differences are the guts and axles....which are all interchangable without modification. Just swap the whole rearend in and go...no need to take it apart unless you're starting with a carrier that has an open diff.

How about gear ratio ?
I own one of the first Miata's ('89). It is in good shape but the differential is noisy.
Also I plan to do a turbo upgrade next winter and I wan't to change the diffmounts so I'd better be ready and do it right in just one transplantation. If you keep the stock 5 speed, does changing the differential change anything at all ?

First, you'll want a 1.8L rearend. There are a few gear options that are easily found with a quick SEARCH around here or Miata.net. I'll let you find the details, but you've got 4.3, 4.1 and 3.9 all available with LSD.

I read that the only difference is the axles from a Torsen to an open? true?
ABS axles different from non-abs? - I would imagine so with the ABS rings...

D

Same axles with ABS ring gears is all.

you just need a rear from a 94-05, axles, and the driveshaft. very simple.

Sounds like I'm all set.....until I get the OS Giken that is..