When I put the truck in gear, you'll have to raise the RPMs up a little bit just to get it moving. Then when your driving it the truck slips out of gear and goes back in. What could be the problem?
My car has 222000 miles.
My car has an automatic transmission.
Based on your description, I think one of two things is happening. Either your transmission fluid level is low causing the slipping or there is an internal transmission issue. I would start by checking the fluid level of your transmission. If the fluid level is low, top it off and see if the problem goes away. If not, I would recommend having your transmission inspected by a qualified transmission repair shop to determine the cause of this issue.