I have two mac 1/2" impact wrenches. I have mostly used the aw434b but I think it's starting to get weak so I dug out the other one which is a aw234a. I got to wondering what the differences were between the two, but I'm not really finding any info on the net. I figured the 434 was a natural progression of the same tool or something. One thing I did know for sure, the GJ board could help me out.