i installed a used transmission in it and now it wont go into any gear i checked the fluid and its good and i took the top line off the trany cooler and it has good flow changed the nuetral switch. i cant figure out whats going on i got the trany out of a 1999 suburban and put it into a 2002 avalanche everyone i talked to said they are interchangable i put the bellhousing and the tourqe converter off the old 02 trany on the 99 befor i put it in so any help would be great thanks