Trani

Hi all, here is my problem, My 740 B230FT is dead, coolant went in to the transmision from the radiator ATF, a change the radiator, flush the trani, new filter new oil, new gascket, the works, but the trans. filter still get derti, I run the car for a day or so, and the car stop changing gears, and there is this buzzing noise, so to the home garage again, oil out, open the pan and the filter is completly derti, clean the filter and do all over again, I clean the sistem 3 times, same problem, but now I have one more problem, the car does not want to go in reverse, and the buzzing noise stil there, no matter what I do is the same, is my trany dead. Can any one help me please, Thanks in advance.