Good morning, the term A/R number is a build of engines, transmissions etc. with Caterpillar
equipment. It use to be stamped on all the engine metal ID Tags. Than things were changed
with engine ID. with just a stick on tag with engine S/N number and same number is stamped
on engine block. The engine s/n and a/r number will always get your build of your engine correct
part made for that s/n build. ( just using engine s/n for some main parts, there may be 7 or
8 part made for engine s/n to choose from and all will fit in different ways.)
For Beaver members I have provided many with the build date of there engines , information
and the A/R number, many times to correctly answer post on engine problems, I always ask
what is your engine s/n number. This way I can provide correct information and part numbers
pertaining problem. To many answers again that I provide tech support many answers will
depend on what the engine S/N number. Dave Atherton Retired Cat Mechanic