Will 4/0 SER 4 wire fit in a 2" I don't know how to size the outer sheath? What size splice box would you recommend to splice 4/0 in? Im switching from USE-2 to SER. And lastly can you drill a 2 1/2" through a rim Joyce? Modular homes... screwy! 2 1/2" since 4/0 triplex with a #4 urd won't fit in a 2" by code.
Please clarify what URD you are trying to pull through. Did not do any calculations but pretty sure I have done exactly what you seem to be asking about many times. Now if you consider the URD to be a single cable assembly then 2-1/2 inch may not even be large enough as you need to use 53% fill for a single conductor/cable, which I think would apply if all conductors are arranged so that they have to pull together.
If you have a URD triplex that has to be pulled as a single cable assembly plus a separate 4 AWG EGC, (which is what I think you were trying to describe) then you essentially have 2 conductors and a 31% fill limitation.
I often use XHHW conductors though and not URD so that makes a difference as it can use 40% fill. But if you untwist your URD conductors you are going to be in the 40% application. Main place this comes in handy is for making turns in conduit bodies or pull boxes.
A SE cable will be a single cable and 53% fill applies and will not pull through conduit bodies unless oversized. There is no fill limitation on a protective sleeve though.
Also beware of the mentioned requirement for an insulated EGC if it applies to you.