The MCT at LAX is surprisingly short at 35 minutes, because all DL operations are contained in a single terminal (T5):
DL-DL DI .35
The only exceptions are connections to partner flights departing from other terminals (which would only apply to you if you were flying Virgin Australia on the LAX-SYD segment) or to incoming flights on partners (e.g. if you were arriving on WestJet or Alaska).
So you are exactly at the minimum. You'll be fine if everything is on time, and honestly for a flight to Sydney they would probably hold it if the inbound from DTW is only a minute or two late anyway. But you could still call and ask if there are alternative, safer routes; if you booked this itinerary at these exact times, they likely won't change anything, but if a schedule change has occurred since booking it's likely they'll offer to move you to something earlier.