On my 89 volvo 240 (auto) the tranny leaks. It runs great but does slip when the fluid is low. Kinda like my reminder to check the fluid. LOL I have been having to add a quart about every week or two. I am not getting any transmission fluid leaks on my driveway. It's a new driveway so I would know. But the underside of the car and rearend is very greasy. I'm not burning transmission fluid it's leaking somewhere. Where are the most likely sources for the leak? And how hard is it to replace for the average weekend auto hobby guy?

Thanks