AC Howling

[PbFut]

Compressor just started howling. It look me a couple miles to figure it out but for sure the compressor when engaged.
I know only enough about ac to be dangerous to myself. I rebuilt the system and self charge the system with proper amount of pag oil but not 100% sure it was correct viscosity. I was testing a new torque converter when it happened. Obviously unrelated but when it rains it pours.
A quick internet search seems to indicate an over charge, but I don't think that is correct. Pressure is 100 each side off and 50 low 200 high while running. I am using an oem a6 style compressor and R zero newer type refrigerate. The system works very well in 100+ so cal heat. The components are quiet when not engaged. Does anyone have a suggestion? Compressor is a 4 seasons from Autozone under warranty.

[howzzzit]

I had the original Frigidaire blow the front bearing twice. Picked up a replacement at Oreillys (then Kragen) installed it and it blew oil from the front seal all over the motor and hood. Took it back and they gave me a replacement. Same thing happened. Received a refund and bought one elsewhere. Had a double lipped seal installed before I put it in. No problems. Running R12 still. Sorry I rambled, but to answer your question when the bearings go they let you know. It was much quieter when off, but I could still tell something was not right. I changed the bearing myself the first time. Not too difficult, but requires the right tools. Brother in law was a GM service manager.

[PbFut]

It doesn't sound like a bearing to me. It is rpm affected. Compressor is under warranty. Clutch is off a 18 month old compressor I had sourced but had a bad front seal. Autozone had an exceptionally good price on rebuilt compressor without clutch so I swaped on the clutch. It worked exceptionally well all summer. I am thinking I'll drive over to Autozone and let them hear it. Pull the compressor clutch and have them warranty the compressor. I just did not want to do so if someone here with more knowledge on ac steps up and offers a different idea like incorrect pressures or some other cause I may not have knowledge of.
If not I'll pay someone to evac the system. I'll replace dryer and warranty compressor and hopefully have the same shop refill system. I hate to say it but probably way cheaper to vent the rzero, refill and deal with the guilt.
One question is what viscosity pag oil should I use if I warranty replace the a6 compressor.

[howzzzit]

Does the new compressor come dry or with oil? Why don't you use R134? It will be phased out eventually, but you could tuck some away. Get hold of the people Autozone buy from and ask them what they recommend for oil.