Which ARB's are you referring to? I have one that is about 4 or 5 years old, and the gear sets are the same. When did they change?
You have an ARB for what axle?
Here's a good thread that shows the difference between the newer style design and the older style design:
ARB RD36 has been discontinued? - Page 3 - Pirate4x4.Com Bulletin Board
The specific parts shown in that thread are for the d60. The old style 9" vs the new style 9" ARB design is very similar though. There is much speculation on the durability of the new style D60 and 14 bolt ARBs based on how poorly the new style 9" design has performed. Time will tell how well they fare I guess, but in my opinion it was a poor design that they went with to cut costs and increase part commonality between units.
***This is simply my opinion based on what I've seen.***