strange noise

[87sierra]

okay as I was on my way home tonight I heard this whistling/ squealing noise coming from the back of the engine or front of trans area the sound would change pitch as I got on and off the throttle and as I braked the noise also occurs when in park reverse neutral and drive almost sound like its coming from the distributor the oil pressure also dropped to 30 and then below 30 and it normally is between 30 and 60

 

[HotRodPC]

Sure hope it's not trans noise. You've got a 700r4 right? Trans working OK? Do check your trans fluid though. Could be a Torque Conveter or Trans Pump Whine for being low on fluid.

Noises like you're describing are very hard to diagnose via internet. And even sometimes in person. Rest assured though, it'll eventually become apparent what it is when it get's worse. Be sure to check all your fluids and keep an eye on the Oil Pressure gauge.

 

[87sierra]

no I don't have a 700r4 I got the th400 and I did check the trans fluid it was at the proper level and so is the engine oil

 

[HotRodPC]

no I don't have a 700r4 I got the th400 and I did check the trans fluid it was at the proper level and so is the engine oil

Even a Th400 can have that TC whine, so can Th350. Not sure that's the noise you're talking about but just saying, it could be. It's not much of a squeal sound though. Usually more like a whining than a squeel.

 

[chengny]

almost sound like its coming from the distributor the oil pressure also dropped to 30 and then below 30 and it normally is between 30 and 60

The above statement concerns me and makes me think that the issue is an internal engine one rather than in the transmission.

Assuming that engine RPM is normal, it would indicate that the oil pump is not putting out. The whistling/squealing sound could be due to failure of the oil pump coupler.

That is the piece that connects the bottom of the distributor shaft to the oil pump drive shaft.

I would pull the distributor and see what the bottom of the shaft looks like.


And, if the oil pressure remains low, I would not drive it. It may drop to zero without warning.

Plenty of oil in the sump and a clean oil filter installed?

 

[MrMarty51]

Also, check for vacuum leaks, they too can sound like a squealing-whistling noise too.
Can of ether{starting fluid} works the best, spray a little around the area that the noise seems to be coming from.

 

[87sierra]

there is plenty of oil and oil pressure is good when the engine is first started and it wont make the noise all the time when I started today it was fine until I turned on the headlights then it made the noise just that you could hear it but when put into gear it got louder

 

[foamypirate]

Turning on the headlights would add electrical load. I wonder if your alternator bearing is going bad. My truck made a pretty good engine RPM related whine when mine was going out.

 

[87sierra]

okay so I listened to everything I could using two extensions as a stethoscope and the only whining noise was from the AIR pump what wasn't noticeable unless I used the extensions to hear it I also found a vacuum leak which might have been the problem since it has not made the noise since

 

[89Suburban]

Hopefully that was it, good job.

 

[87sierra]

I believed I solved he problem noise due to vaccum leak but is it possible for electrical load on an alternator to drop oil pressure slightly

 

[89Suburban]

I believed I solved he problem noise due to vaccum leak but is it possible for electrical load on an alternator to drop oil pressure slightly

Good question. I swear sometimes when I turn my turn signal on the oil gauge needle flutters.


Posted From Hell

 

[MrMarty51]

Might be that the idle changes ever so slightly lower, or, possibly some slight grounding issue.
Hook a mechanical gauge to it, that`ll tell just what it really is doing. Do`nt worry about how accurate the mechanical gauge is as far as the actual PSI compared to the factory gauge but rather, see if the mechanical gauge drops pressure like the factory gauge.

 

[MrMarty51]

Turn signal on My 93 will cause the volt meter to bounce.

 

[87sierra]

Okay so today my oil pressure dropped to 15 psi and it would stay there unless I realy got on the throttle but would go straight back to 15 or a little above. I check the I oil and it is at the proper level and the whining noise is back slightly