AC making moaning noise

I have an issue with my air conditioner on my 1989 GMC Suburban. Here are the current facts:
Converted to R-134 Compressor replaced (2x) Condenser replaced
Dryer replaced Orifice tube replaced
The issue is that whenever I engage the AC, there is a lot moaning noise through-out the system. This noise has been present ever since I converted to R134 and replaced the components above. A mechanic first mentioned that the new compressor might have been bad. So I replaced it again (part was under warranty). After we flushed and evacuated the system the sound was still present. All tests are reporting good. Could this be caused by too much oil in the system? When I replaced the compressor and dryer, I did fill the system with the factory recommend 8oz (4 in dryer and 4 in compressor) of oil. I did tell the mechanic this before he charged the system, so I don't think he would have put more in there.
Thoughts?
Thanks, Mike Thompson 1989 GMC Suburban 3/4 Ton
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On Fri, 07 Sep 2007 08:37:27 -0700, snipped-for-privacy@gmail.com wrote:

A system pressure check is in order. If it is over pressured it will moan. What are high and low side pressures running? Also, 8 oz is a lot of oil to add the system unless everything is new and dry. When you replaced parts did you use a 1993 on R134 compressor, expansion valve and condensor? These are bigger on R134 system because to try to make up for reduced efficency of R134 vs R12. BTW, I have a 89 4x4 burb that I bought new and there is no way I would ever convert it to R134. ----------------- TheSnoMan.com
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Johnsons Freeze 12 is the way to go http://www.freeze12.com / 1981 K-20 blows 38 even when it's 118 in the Las Vegas heat! Purge the 134 and fill it with freeze 12 you will be happy
Dave Las Vegas NV. Home of the "DRY MUD" It's called Sand

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wrote:

Lucky you have very low humidity and it a lot easier to cool the air there as humidity increases the work load a lot on refrigerant. Not sure what you would gain with Freeze 12 in a R12 system since it is ablend of 80% R134a and 20% R142b and R134 is set to be banned in 2012 or sooner. ----------------- TheSnoMan.com
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