I have a 92 f-150 custom ford with a 4.9 straight six. It seems when I go to put it in reverse it acts like the cluch is not fully engaging. this has a manual trans. is there an adjustment for the cluch. once in a while it will work fine but most of the time it is hard or grinds when going in reverse

The clutch is not releasing fully when changing gears. Does the pedal go down quite a way before it seems to be contacting anything? The reason the forward speeds don't make noise is that they have synchromesh gears, which is a pre-engagement mechanism that allow smooth noiseless shifts (up to a point anyway!). I think this a hydraulic clutch mechanism and the lower slave cylinder at the clutch bell housing is the adjusting point for correcting the clutch free play. It should be set so that the internal release arm is nearly touching the throwout bearing inside the bell housing. The problem may also be that the slave cylinder is loose on it's mounting. The clutch pedal should move about 1/2 to 3/4 inch before it starts to push on the shaft from the master cylinder. Hope some of this helps!