Transmission slip problem

[hhazz]

1996 explorer 5.0
When I put my car into drive it slips before it will start moving. Once I am moving the transmission shifts fine. It does not do it every time. Transmission rebuilt by ford year ago. I do need to have a rear main seal replaced. Any ideas

 

[Stephen S]

The "slip" that you are perceiving may not be a slip at all. Is it just a second or two hesitation before you feel the tranny engage into drive?? If so, that's probably normal. There's no slipping involved, it just takes a second or two to engage. Mine has always done the same thing. A fluid and filter change may improve it slightly.