How do you know the oil's ok? Has it been changed, sump dropped & filter cleaned? If not you don't know it's ok - http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=30096 are you checking the level with engine & box warmed up & running? Does the hold light come on when you press the hold button? (just to check the bulb hasn't been tampered with or failed).
You can't polish a turd - but you can roll it in glitter.