I'm using a 36GB Maxtor LVD drive on my 4000 and it works flawlessly. I can't remember what I jumpered, though. I think LVD/SE should auto-detect anyway, but Force SE jumpered is probably wise.
Make sure you have TermPwr enabled on one of the disks, active terminators either end, and a good SE SCSI cable (don't know if an LVD cable will work). Then set the ID, and go into the CSPPC's SCSI menu by holding Escape while booting, and make sure everything is set correctly there for the unit the disk is on.
Keep trying, though - as long as your SCSI chip is working it should be ok as it's pretty similar to what I'm running OS4.0 on.
