I have lifted 3800-4000 pound rock pallets with an 863 with metal tracks. We had a JD 310 backhoe on site and it couldn't unload the rock pallets off the semi trailer. I used my forks and though it groaned and creaked, I lifted the pallets and didn't tip. If your machine is in good condition, it should do it but I imagine you will start tipping. The lift arm geometry isn't suited to that extra weight as well as a vertical lift machine.
"You Can All Go to Hell, I'm Going to Texas." --Davy Crockett