When I bought my '02, I knew it needed a new rear 3rd member. When I started looking, I discovered there were 5 gear ratios from the factory based on engine, trans, drive, wheel sizes, and maybe 27 other options. Mine is a 4WD SR5 with 3.4 5VZ that came with the 15" aluminum wheels and the A02A axle code, which ended up being 3.91 gears, which is not common for 4WD models. I had to rotate the wheels while it was off the ground and count the rotations of the driveshaft and then divide by two. I ended up getting a used 3rd member out of a 2WD pickup from a salvage yard in CA that was then shipped to me. I still have the bad one in a box in the garage if you want to just get it rebuilt and it's the correct gear ratio. Buying a good used one was cheaper than rebuilding the one I had, at least that's what I convinced myself of at the time.
This is the axle code cross reference I found:
3rd Gen Toyota 4Runner Axle codes:
A01A - 3.73
A02A - 3.91
A03A - 4.10
A04A- 4.30
A05A - 4.56