Your comments and suggestions are welcomed, no need to be sorry. My slipper is set correctly, I'm pretty anal in checking it often. I can hear it work constantly when I get on the throttle. That short ''whizzzz'' it makes when it slips. I will check my punch control settings and I will probably make sure my slipper is set correctly again (anal I told you).
I will definitely not avoid running on any surface I wish to though. But maybe I'll try to remember to take it easy on high bite stuff. I feel that a construction site where I bash most often is the worst for the drive train. Sand, rocks, dirt, wood, piece of concrete, bumps, ruts, hills etc. All these give different traction to each wheels. Slip, grip, slip, grip a lot, grip a little, slip a lot, slip a little, grip a lot, at a different rate for each wheel all the time, I think that is way more difficult on the diffs then the linear traction you get from asphalt or concrete. I may be wrong but I noticed that I never seem to break drive train parts on concrete, asphalt or grass, always when I go have fun in those construction sites. Anyway.
After I opened the diffs and cleaned every part, it was obvious that it was the spider gears again that stripped a few teeth which caused a little damage to the output gears. Here's what I'm going to try, I had a couple sets of rebuild kits for the Thunder Tiger S3 buggy and I'm going to try those spider gears. After comparing them with the Losi ones, they seem better made with more meat on the teeth.
The Thunder Tiger spider gears are on the left
Here's a different view that makes the differences easier to see. Both gears have the same number of teeth and the same pitch. But the Thunder tiger spider gear has a slightly bigger diameter and is thicker. This results in the teeth being longer and having more surface to mesh with the output gears. I hope that it makes them stronger.
The Thunder Tiger diffs also use thin shims behind the spider gears and the output gears. So I installed the shims and the spider gears from Thunder Tiger and all the rest is Losi diff parts. It all seems to work together and the diffs are very smooth. Now to go out and try them.