I have installed a 5-speed 4x4 transmission in my trooper 4wheel drive works as well as 1st,2nd,5th,and reverse gears when i shift it into 3rd,and 4th in acts like it in in neutral does any one else ever had or knows how to fix this problem? I would greatly appreciate any advise you could give me thank you

 

Replace with new filter.See if it is ok.I found a small piece of cardboard in a old mustang once.Sometimes take a week to act up.two pumps and removing and checking the filters many times.But found it.