700r4 knocking in P and N
I have a 1991 caprice classic with 305 engine ( around 80 000 miles ) and in this summer I have lost a reverse on my 700r4. Transmission has been rebuilt a month ago and everything is fine now except one thing. Now I hear a knocking sound when transmission is in N and position P. It's pretty loud sound like someone is banging on the metal with a hammer. When I shift into gear D or R this noise disappears or it gets really really quiet. What can this be ?? Is it pump, converter? Is it harmful to drive a car in this condition ?
Thank you in advance!