I was given a 97 F-150 4.6 by my brother after he rolled it over. I fixed it but it was not running for about 1 year and a half. When we first started it ran fine . All the gears shifted fine but now it will not go in reverse. I changed the transmission fluid and the filter but it does the same thing. When I place in on reverse it sounds like if it clicks into gear but there is no movement.