GT what?

Hello all! I have a 1995 z28 hardtop automatic tranny. The engine is making some type of scraping sound? I do not have a stethoscope but I did put a bar to the valve covers and can not notice anything out of line. It sounds to me that the noise is coming from the rear of the engine... It does not affect power and is not present at startup. Once the engine heats up, the oil pressure drops to about 20 and the engine makes a chopping sound. Almost sounds like an 18 hundreds locomotive taking off! Any advice or personal experience with this would be greatly appreciated! I know this is a very vague description but I don't know how else to convey the sound. I have had it looked at by 3 "mechanics" and the best answer I've gotten so far is: the flywheel might be loose. Noise dissipates @higher rpm/oil pressure.

Injuneer

Fully warmed up... you indicate the oil pressure drops to 20psi. At what RPM? If that's at idle, it's fine. If that's not at idle, what is the pressure at 2,000 RPM.... at 3,000 RPM.... at max RPM?

Is there any evidence of the transmission slipping?

GT what?

Yes this is at idle. 7-900rpm. Pressure jumps up considerably when revved or under a load. Transmission shifts awesome! Car is in awesome condition inside and out I am the second owner. Very strange noise I never heard it on any other vehicle

GT what?

103k

Fatdog2

If you feel the serpentine belt is old I would hit it with wd 40 ever so gently while the noise is present.Next I would loosen the belt at the tensioner and spin the pulleys by hand and check for wobble.Noises travel in these cars kinda weird but it kinda sounds like the air conditioner may be going south to me.I was lost when I heard all this banging and clacking noise on my old bird and it turned out to be a disintegrating cat,all the noise from the engine bay.Hope this helps.

cheapchevy

Try removing the serpentine belt, then start the engine and listen for the noise. This will eliminate noise from the accessories (alternator, a/c, pwr steering, tensioner pulley) and help troubleshoot noise source.

GT what?

Brand new serpentine, all pulleys and idler inspected. A/c is the only thing that does not work on car. .. but the pulley checks out ok. I really appreciate all of the input! What caused your cat problem fatdog2?

Fatdog2

Blasting it from a roll I believe all the time.It had about 80,000mi on it though.