oil pressure issue in 93 sub 5.7

I Had a weird experience the other day and was trying to come up with a reasonable diagnosis, so i came here. I wasdriving my 93 sub with the 5.7 aprox 240,000km. All of a sudden something under the rocker covers started making a horrible clicking noise but it eventually went away. Oil pressure was fine at this time. The next thing i noticed was when i had the cruise on and climbing hills at highway speed. The oil pressure dropped drastically to almost the red line when the tranny downshifted and the revs came up from 2000 to 3000. It was very consistant at doing this only while climbing hills and the engine reved up. If i used my foot to gradually press the gas it was fine. I kinda always thought that the oil pressure would rise up not drop when the engine reved up. once coming to an idle it would drop slightly just like most engines would.

Is my oil pump getting tired? Can i change the pump without pulling the engine?

Thanks guys

I Had a weird experience the other day and was trying to come up with a reasonable diagnosis, so i came here. I wasdriving my 93 sub with the 5.7 aprox 240,000km. All of a sudden something under the rocker covers started making a horrible clicking noise but it eventually went away. Oil pressure was fine at this time. The next thing i noticed was when i had the cruise on and climbing hills at highway speed. The oil pressure dropped drastically to almost the red line when the tranny downshifted and the revs came up from 2000 to 3000. It was very consistant at doing this only while climbing hills and the engine reved up. If i used my foot to gradually press the gas it was fine. I kinda always thought that the oil pressure would rise up not drop when the engine reved up. once coming to an idle it would drop slightly just like most engines would.

Is my oil pump getting tired? Can i change the pump without pulling the engine?

Thanks guys

First thing I would do is hook up a oil pressure gauge directly to engine in place of the oil sending unit and check oil pressure. Attach it to the windshield some how and watch the pressure while driving under the same circumstances you discribed and post back findings.

Could be oil pump getting weak, bad main bearings, camshaft bearings or lifters.

2WD or 4WD. Check out the online service manuals for procedure to replace oil pump. I believe you should be able to remove oil pan without removing engine.

thanks for the reply, after searching around it sounds like putting another pressure guage on seems to be the first thing to do. I'll try that before i get carried away changing stuff. thanks again..