HELP!!! Knocking and vibration not from CV joints

Help!!! My 89 Cabby is knocking and vibrating even at low speeds, 10-20mph. Gets louder and knocking faster when accelerating. Have changed both inner and outer CV joints and replaced front engine mount but although there's a small improvement, the vibrating and knocking still occur, but a little quieter.    What else can be causing this, I want it sorted but with limited funds I can't afford to buy parts if it's not going to sort out the problem. Any help most appreciated.  

When the gearbox in my GTI finally expired at @190,000 miles the symptoms were very similar to a failing knocking CV joint. Drain the oil from the box and see what come out, dark over heated oil or fresh clean oil? Any metallic bits?