I have a 1988 d 100 with a 3.9 and a manual trans (4 speed with OD).I had to have a rebuild 4th and R went out. I have the truck for about 1.5 yrs and has all ways made a noise in gear(not 4th) or out with clutch out,sounds like a diesel. It is still making a noise and took it back. He replaced the out put shaft bearing and still makes the sound. He does not know what or why. Said maybe it is suppose to make a sound. Does anyone know and if you have this motor/trans does your truck do this? thanks