I have one of these Rubbermaid 2640 dollies and a wheel bearing went to crap, on me. My question about your product is this: How long is the threaded stud on your replacement wheel? The original wheels were a press fit with the stud length measuring 1 3/8" from end of bearing race to the end of the stud. if yours is threaded, I would need it a little longer to get a lock washer/nut or a nylok nut on it.
The 2640 dolly new caster (part number 3530-L1) has the dimensions of 1.03" long stem with 3/8-16 thread. If you are needing a defective or an assembly replacement caster or if the caster is the nut and bolt design you will need a 3530-L1. If not you will need to replace the entire unit.
Hope this helps!