I have built a 91 smoker pretty much from the ground up. Got the frame/ cab from junkyard. engine was gone. Tranny still there. I hooked in another engine,everything runs great. I have a water in fuel light that wont go out. (not too shabby) Most of my issues come from the tranny. I think its the 518. it is supposedly four speed overdrive. It worked ok for about three months. then starting hard downshifts while slowing down. I have never felt them that way before. Then it started slipping really bad. to a point it would not tow, or get out of its own way. Now it shifts through the gears very quickly and will not downshift at all. I checked the kickdown linkage, its fine and operating. Is this just another case of replace the junkyard tranny, or am I having a common proble. I did replace the filter and fluid. And the torque converter came from a truck the same year and make that was driving great. Any help would be greatly appreciated.

 

Ok, update. There is a kickdown linkage cable that goes from the tranny to the throttle. there is a tiny white lever on the back of the bracket of this cable. It needs to be taken loose and reset. My buddy found it in the haynes book. My truck drives like new. hooks up in all gears. If anyone is having trouble with their tranny, I suggest looking at this cable. According to my buddy, when I had the throttle open, the fluid was not building pressure and bypassing. Hence no power. Good luck.