Hi there I'm new to this site I have brought an 89 F250 back from the dead hasn't ran in over 4 years I've done a lot of testing and got it to start then I got it to run I took it for a test drive finally after 4 months it goes to 1st gear 2nd gear 3rd gear with no issue but I cannot get it to go to the next gear RPMs go all the way up to 3500 to 4000 and it will not shift any further the speed is about 55. I'm not a mechanic but I am mechanically inclined I'm stumped and don't know where to go from here is there anybody that can help me to guide me in the right direction