My inline 4.9 F has been sitting for about 4 weeks until today. I needed to use it for a 60 mile round trip. Everything was fine until I got about 20 miles out when the oil pressure gauge went to 0 and the truck started knocking. While it didn't seize up, it has little or no pressure. I didn't dare drive it any farther, so I called a tow flatbed to haul it home for me.

A friend who works in a boneyard told me to drain the oil, put 3 quarts of oil and 2 quarts of tranny fluid into it, then let it run for a few minutes. If it still doesn't have any pressure, then the oil pump is shot and needs replacement.

What do you all think? Should I try this, or just take it to a shop and have them replace the pump?(I don't have the tools to raise the motor and pull the oil pan?)

 

I don't know about transmission fluid. I used a product called Motor Flush in my 4.9. I lost oil pressure, got the ticking, and it was because my 4.9 sat for 4 years, and the oil screen plugged up. I put the motor flush in, as per the directions on the can, and then changed the oil. All is good now. The oil pressure gauges on our style trucks are not really gauges, but on/off indicators. It will give you an idea if you have oil pressure, but it won't vary at all.

Incidentally, the 4.9 uses 6 quarts, so 3 oil/2 tranny fluid would still be low.

 

By the sounds of what you are discribing you most likely threw a bearing. Flushing it with anything will make very little difference.
If it was just ticking (top-end) I would say try flushing it and change the oil but if it is knocking on the bottom the only solution is pull the pan and see which one is bad and replace it.