Diesel oil pressure.

[Hooligan]

 I just motored from Jacksonville Fl to Brunswick Ga.  My new Walter V drive runs great but I am having a problem with my engine. Oil pressure starts out at 60 psi after it warms up it drops to 10 psi. And the gauge needle starts bouncing I thought it may be the sending unit so I installed a mechanical
Gauge and it is the same,    the needle does not hold steady. Does any one know what may be causing this?

[SVJourney]

That's a new one on me. 
How old is your oil and what viscosity are you using? 
The only other thing I can think of is that the oil line to the steel block where your sender screws in might be getting blocked with sludge. 
Oil press does normally drop a little with warm oil, but not that much.
Jumping needle at the bottom of the gauge is generally when you are out of oil but I assume you checked your dip stick carefully.
The oil pump itself is pretty much bullet proof.

[DeanA]

Sounds like low oil level at the pick up in the pan after the engine has been running (highest level in the pan will be before start). There might be a plug (sludge) in the pickup. Might not be a pump problem since you do get good pressure early.
Maybe try simply things first- change oil & filter. Auto parts stores sell various 'cleaners or flushes' to reduce sludge.

[Hooligan]

 The answer is, the oil and filter are new, the Wt. is  15/40 and it is topped off.  Since i posted that I have motored 1000 miles so if had no oil pressure my engine would be toast now.  it must just be a bad sender or gauge. Thanks

[PeteW]

I would start by monitoring the 12VDC supply to the gauge. Clip on right at stud on the gauge. Ground the voltmeter to the engine block too.