How do you know if it's your transmission or something else on a 07 dodge caliber

Hello, if the engine revs in gear and there's no movement, it sounds like no transmission engagement. If the engine does not rev, then it sounds like an engine performance issue. All that to say - it's impossible to know in your case, because you're saying both happen. So, hands on testing is needed. Which is true anyway -- there's nothing you can do without professional assistance. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops