134A R4 conversion seal failure?

[LarryP]

I put a used R4 that was most likely from an R12 system on a 93 Chevy truck Flushed the compressor and system changed the orifice tube and accumulator, added the pag oil evacuated and charged. It worked great for maybe two months, then overnight was barely cooling. Added a can or 134 and it was cooling great again. For a few days Long story short--every time I added it lasted about half as long
Found the compressor shaft seal leaking. Finally just put a new comp on and all is well. Getting another 93 truck that seems to be still r12, but it is empty. It has been sitting for several years. The clutch hub is not oily at all. Question is---if I convert it to 134 is the seal likely to start leaking? is it likely that is what caused the seal to leak in the other compressor. I had used EnviroSafe and DuraCool in the past, but have had several compressor failures with them, and am not planning to use them any more. Agree?

[GM Tech]

The seal leaks because it is not a double lip type seal. All GM shaft seals went to double lip style in '96- so you can replace the seal with a seal kit you can easily buy online. The type of refrigerant is not what causes the leaky shaft seals.