what would make a transmission slip?
on 1997 Ford Explorer

Boyfriend drove my explorer and came home and told me that it wasn't shifting properly. Truck has been sitting for 5 months now and he drove it today and it ran fine. Possible problems?

2 answers
ck fluid level and also see if its burn't and smells bad
due for a tranny flush maybe. review when tranny was last serviced. might be a clue there. further if you are going to be leaving it sitting for any length of time, is good practice to run vehicle at least once a month to ensure everything stays lubed.