And was there a difference between the Turbo transaxles and the NA ones (and the 968s, for that matter)?

 

try searching there is 30 years of info on this.
but basically, the NA trans is barely capable of holding the stock NA power output - my original trans grenaded the diff while coasting at 70mph on a long highway trip, drove fine for 60 miles and then BAM locked up and shredded teeth.

the 944S has roughly the same gear ratios (slightly taller) than the NA but is a more robust gearbox.
944 turbo and 944S2 have roughly the same gear ratios (but not actual parts) as the 944S but have different diff ratios, 3.375 and 3.875 respectively (NA/S is 3.89).

turbo and S2 are the strongest 944 gearboxes, especially the 951 AOR box with hardened internals and LSD.

968 gearbox is a completely different design entirely, 6 spd.

 

Spencer, the 944S has the same internals as the 944S2 and 944 Turbo gearboxes, with the exception of the ring and pinion set. It is different in each of the three.

You're correct about the eight-valve, normally-aspirated gearbox: its pinion was marginal but holds up well if the transmission is well maintained. However, I have a replacement for it that has the same ratio, but stronger (wider tooth root) pinion. Basically they took the 944S ring and pinion, and shortened the pinion shaft to fit the eight-valve, normally-aspirated gear stack. Nice upgrade for the racers. Cheers,