When I was talking about R12 and R34 AC it reminded me of a bad experience I had and I wanted to let everyone know what happened.
I had a transmission cooler installed on a 92 chevy C1500. It worked fine for about 18 months and I imagine it helped my tranny with the towing it had to do every so often. The problem began when trying to find a leak in AC system. Turns out that the oil cooler wasn't installed with any type bushing to buffer a space between the AC coil and the oil cooler. It eventually rubbed a hole in the AC coil. Well that was about the time that R12 became expensive and not only did I need a new coil but had to switch the system over. I notified Mr Transmission about what happened and they sent me a formal lawyer letter stating that they were certain that their cooler had nothing to do with my AC failure, (even though the hole in the AC coil was directly behind the mounting bracket for the oil cooler). So I have told everyone that will listen that Mr Transmission does crappy work and therefore will not stand behind it. THERE.