I'm interested in a Suburban or Yukon XL with the 8.1 and 4.10 gears for a tow vehicle. I'll occasionally tow it's max rating of 12K pounds but only local and very few miles per year moving a tractor or mini excavator between a couple of properties for clean up work. I'll use it mostly for towing much lighter loads like maybe pulling four ATVs and camping gear up in the NC, VA and WV mountains. 1. Is there an axle code on a label somewhere that I could get a potential seller to give me relatively easy? I'm sure I'll have to travel to find one of these rare unicorns so I'd like to know the gearing before making a far trip to check one out. 2. Did all the 8.1 Suburbans come with the 4L85E tranny and what's the difference between the 4L85E and 4L80E? 3. I think I read that the 6.0 equipped models had a 14 bolt semi floating axle and the 8.1 came with a 14 bolt full floating axle, is this correct? 4. Can you share the good and bad about the 8.1 powertrain or at least what to look out for and expected failure areas. Thanks for any information you can share.