I have a 92 F150 4x4 that has trouble in reverse. When I shift in to reverse it takes about 5 seconds before there is any pressure on the tranny, and then when I push the gas it backs up slowly, if on level ground, or not at all if backing up hill. What I find strange is that if I put it in 4 low, it will back up any hill!! I don't think its a transfer case issue, and the transfer case was rebuilt only 4000km ago. Any ideas? Thanks!