A-518 and 46RH find

These are just the two different numbering systems used for the same transmissions. The 518 number was based on the old number, like 904, 727, 500, 518, etc. The new numbering system related more to the intended use, so an A500 was now a 42RH and an A518 became a 46RH, but with the V10 and diesel engines they also added the 47 and 48 torque ratings. In the new numbers you can tell the first digit 4 meant four gears, the second digit 6 was the torque classification, the third digit R was for rear output, and the fourth digit H was for hydraulic controlled. Once it went to PCM controlled shifting by manipulating the governor pressure with a solenoid they just changed out the forth digit H for an E.

The 94 model was near the changeover in names, so clearly one got the name and one did not, just by chance how manufacturing changes take place. They are basically the same transmissions, and will take the same components during a rebuild.