Which engine does this Monte have (and if it was listed, I missed it)?

If it's a 3800, check the PCV. It sits very close to the alternator and I've read where others had a similar symptom only to find they were missing an O-ring for the PCV. Corrected the missing O-ring, no more whistle.

 

Its the 3.4 liter engine, 3400 series. I looked at the PCV valve anyway and the o-ring and pcv looked aged so I ordered the O-ring and the tube for saturday since they didn't have it in stock and changed the actual valve hoping just that would solve the whistle. Unfortunately after dropping the tube and spending half an hour looking for it when installing the new valve, it did not solve the whistling. I sprayed some carb cleaner around the pcv valve and around the lines it lead to while the car was idling and there was no change in idle that I could notice.

I've heard that our cars are known for leaking intake gaskets, so are these the symptoms of a gasket leak?

Since I have posted this thread the whistling has gotten louder I'm pretty sure. its high pitched enough that a 50 year old man couldn't hear it. The car does not whistle the moment it starts up. After about 3 seconds the whistling starts pretty loud but then after about 6 seconds or so it subsides and you can hear it if you really listen. I slightly rev it in park and it hisses louder.

 

I replaced the o-ring and PVC valve now and the whistle is still there

 

Did you ever get this whistle figured out? I have an 03' SS and it too whistles. At cold start up, the engine sounds like there is excessive air flow somewhere, but I can't pin point it. The whistle seems to come from the same general area and increases with RPM. It's driving me nuts! I'm chasing a rough idle at start and occasional engine hesitation/miss as well. I'm not sure if the two issues are related or not. I'm hoping you found the cure to your problem and can share what the fix was.
Thanks in advance!

 

Below are things to consider While whistling noises in a car are due to several different problems, a vacuum leak is one common reason for this issue. Vacuum leaks also cause the car to run rough and stall. Worn, broken or cracked vacuum hoses are a common source of the leakThe source of the whistle is sometimes an overworked alternator. This electrical component keeps the battery charged and provides power for lights and accessories. High resistance between the alternator and battery increase its workload, causing a noise that varies with engine speed. To stop this noise, car owners should inspect electrical wires and connections. Any corroded connections should be cleaned, and worn wired should be replaced.Worn fan-belt pulleys make a sound that increases with speed. Worn belts also create a whistling noise. Belts should be inspected for signs or wear and replaced if necessary. Pulleys should be tight with little horizontal movement. Belts should be adjusted to the factory-recommended tension.Noises that only occur as the car is moving are sometimes due to worn window seals. As the vehicle moves down the road, it forces air through these small openings, resulting in the whistle. Windows that are not fully closed increase the chances of whistling. Any worn seals should be replaced, and windows should be tightly closed. If the noise continues, door seals should be inspected for any small holes that allow air to pass.

 

My last MC had a 3.4 with the exact same problem. I sprayed some carb cleaner and noticed that the upper aluminum intake had a small crack. I replaced it with another one I had from a different car and the sound went away completely.

 

I took it to the dealership AGAIN and this time they found everything that is wrong with my Monte. they assume it is my harmonic balancer causing the whistle, my engine motor mounts on the bottom are shot, my transmission cooler lines are leaking, my transmission needs a new solenoid, valve body work, and my injectors need cleaning haha.

The whistling is soon to be solved cause I have all the parts right now to fix it everything but my transmission and I'll be putting some ported intake manifolds on soon also so everything should be covered to stop this whistle! Thanks for the help, I'll update after I put on my harmonic balancer and so forth. Right now the Monte is sitting in the driveway til I get the motivation to do the job haha.

I would have posted back sooner but I have been having troubles posting recently. It was telling me I didn't have permission to post or message people while I was logged in haha, weird.

Also, how hard is it to replace a transmission yourself? I know you have to take the whole subframe down, how hard is that and I'm wondering how much a transmission weighs and how easy it is to take the transmission apart from the engine and put a new one on. Do you just lift it? Do you need a engine rack or a tool? Thanks for the feedback

 

It would be easier to leave it bolted to the motor and pull both. Changing a transmission is a miserable job on a W-body 👎

 

Check for a intake leak by pouring water around the intake gasket areas, you'll hear the difference if it's sucking the water in.
If someone has done the LIM gaskets and not torqued the bolts in proper sequence the LIM could be warped causing the intake leak.

 

So I finally found the source of the whistle, and that it was also the cause of my check engine code for an evap leak I have no clue how I didn't notice it til now. I checked the pvc valve but not the tubing all the way up. Noticed it now after I did my intake manifolds when I had to take everything off.

Also I ended up just taking my car to a transmission shop and got my trans rebuilt with updated parts, oil pan, engine mounts, and stabilizer links.I think it was somewhere around $2200 but I get a 3 year warranty on it.