2006 Ford Explorer slipping when accelerated

Change the auto transmission fluid and filter. Pay attention to the smell of the fluid. If it smells burnt, there is likely burned or worn clutches. You can compare the smell of the old fluid with the new fluid if you're a newbie. it also doesn't hurt to save a sample to share with an expert if you know one. Also pay close attention in the bottom of the pan for metal filings, fragments etc. A fine layer of black silt is usually normal. If the trans is burned out, there will be evidence in the pan. NEVER rev the engine to get an auto to go into gear, and avoid letting the transmission slip at all costs. Overhaul is a major job and very expensive. I don't know why they'd change wheel bearing on a slipping auto. Or why they couldn't diagnose it for you. Hope this helps.