I have a 99 7.3 with a manual transmission. When I'm taking off at low speeds I get a rambling/vibrating/rubbing type noise that seems to be coming from the bell housing or maybe far back in the motor. Only happens in 1st, 2nd, and Reverse (so far that's where I've gotten it to replicate the noise). Has 175k on it so I'm thinking it might be the flywheel or clutch but don't want to go through 6 or 7 hours of labor to find out I'm wrong lol. I'll be pretty specific here. It only happens at low speed. Of I depress the clutch it goes away but there's a pretty loud knock. If I let the clutch out slowly at about 1000 to 1200 rpm, no noise or it's really short. If I let off the gas it goes away. It only really happens if I take off slowly or creep around(I have to do that sometimes, I work construction) and only while slightly keeping the rpms up if I go WOT it jumps but doesn't pop no noise no weird behavior so I'm thinking it has to be the clutch or flywheel. I might be a retard though I don't usually play with manuals lol.