I have a 1982 240D 4speed that had a NA 617 motor installed. There has been a grinding noise that only comes when you load the driveline with power. I replaced the tranny mount, and inspected the driveshaft universal and flex discs, and carrier. These seemed fine. Then I put the car in the air and put it into 3rd gear. One of the axles not only spins, but moves in and out between the cv joints and there seems to be a not so good noise coming from this area. Assuming this is not normal, I am going to replace the axles. On the online order places they list two types of axles. One is a homokenitic, and the other is annular. Do I need to remove my old ones to determine which ones I need?

Do I need to replace seals in the diff? Are the rebuilt ones offerd any good? I read a post about $60 axles rebuilt that may not be good because of a surface that doesn't get rehardened in the rebuild. Is this what I will get if I purchase rebuilt ones from one of these mercedes parts places online?

Thanks.