I thought all 4th gens had oil pressure gauge?

 

did you check any of the other bearings? bounce the crank back an forth a tad In different positions to feel an listen for any bearings clicking. how did the bearing surface on the crank look, smooth and not discolored? also have you tried higher wt of oil, like 10w40 or even 20w50

 

I replaced all of the rod bearings at one. All of the bearings looked the same obvious wear in the middle but nothing unexpected of 30 year old bearings. The bearings for cylinder 1+2 were slightly more worn but overall they all looked really good for being 30 years old.i haven't tried higher weight oil but I did add some stp smoke treatment solely because it said "reduces metal to metal friction" (I was looking for regular oil treatment) my only guess for the knocking to come back so quickly is either crankshaft is ****ed or the oil.pump aint pumping

 

usually the first thing to react to low pressure is the lifters clatter. even so I would agree with you, likely a combination of low pressure and worn crank.

 

I do not know how bad you noise is but you could try some 20W 50 oil? I had a high mile 2.8 v6 back in the day and after it hit 150K the only way I could keep the bearings from raddling was 20w50. I had bought all the parts to rebuild it in case it ever went bad. I traded it in 2 years later with the 20w50 in it.

One thing that seems missed and is a very common issue in GM cars is a stretched rod. This causes the rod to no longer be round and causes bearings to have too much clearance. How bad was pulling the pan in the car? You could pull it again plastic gage the bearings look for ones with larger clearances.

I would not do this unless in extreme life situation but you could lay out a pc of wet 400 sandpaper and slowly sand the caps down. Then re-plastic gages until you get to .003". This is a last ditch effort when you have nothing to lose and time is cheap for you.

Oil pump can be replace with a higher pressure higher volume pump. A gage to check oil pressure can be bought for $30 at harbor freight.

It used to be used motors are cheap, If you pulled the pan and replaced the bearings there is no reason you could not swap in a low miles. Just something to think about. We can point you to several threads to help you.

 

I'm ordering the parts to rebuild the oil pump Friday. I drove it last night out of necessity and once the car got warm the pressure was at 35-45 also I'm not extremely intelligent it's got a oil pressure gauge no temperature gauge
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35-45 would be normal oil pressure, Rule of thumb is you need 10 PSI of pressure for every 1000 RPMs. I do not think an oil pump is going to help you. Assuming your gages is accurate. Can you take a video of the car knocking move the camera from under the hood to under the car. This will let us heard based on position.

Is there metal flakes in the oil? any in the pan ?

 

No metal flakes in the pan or oil. The oil did look like coffee with a lil creamer in it though but not necessarily glittery.
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my raggedy phone won't let me upload videos but I'll try to figure it out later the oil change kept going between 30-35 at a warm idle but bounced the whole time I've no clue what that means

 

I never use the car gage for diagnoses. They are little better than a dummy light. Even back when these cars where under warranty and they came in with "Low oil pressure" complaint it tended to be a gage problem not a engine problem. A jumping oil pressure gage is more likely a gage issue but if it is not I do not see it being an issue at that pressure. THe only thing those gages are good for is if you know what the pressure normally is. you then have a problem. over reved, over heated or ran low on oil. Then you see your gage is now reading low. That means you need to go get the oil pressure checked and get the oil check for metal flakes, chances are you hurt to motor but if there is metal flakes the motor is tearing itself a part.

Craby is right if it was just an oil pressure issue you would hear it in the valve train first. If the engine has too much bearing clearance then as pressure drops or oil thins due to heat then the lower end will get noise. This would not be the heavy knock of a hammer hitting the side of the engine. Just a light knock.

My old 2.8 (which was the engine the 3.4 came from) would drop below 10 PSI at low idle and that was when it make the knocking noise. I just enough pressure to keep the valves from clattering.

Just a heads up, there are two things that kill the GM V6 besides overheating (that is any car) Intake leaking coolant into the oil and stretching rod/rod bolts. If the rod bolt is stretched then all this becomes a waste of time and effort. The bolts can fail in slow motion. It will get a tiny bit worse every drive. If you can get the knocking to stop it may add some life to the motor but not much. You will spin a rod bearing.