Problems with the reverse of the Dakota

Hello everyone, I have a 2005 V6 3.7 day ago I tried to go back to a slope and suddenly I left without reverse, hooked her and makes a small "Clunk" but does not hook. Change the liquid and clean the filter and do not improve, there are no error messages or anything, the rest of the speeds and the 4x4 work although it makes a noise in 3rd. I hope someone can help me. Thanks in advance.