I have a 2012 charger magnum racing Jr3 flat I switched from a thick wall axel to a thin wall I had been losing corner exit speed but could not figure out why until I remember switching axels could this have done it or am I missing something?
It appears your original post is an answer if not, the answer. Switch back and see if it helps.
I like to think and write about the why of it. Your first post said Jr3. That indicates to me a lighter driver. To get weight on or off the LR, the weight of your driver, your speed on the track and how tight you turn are the main sources of power, to do it for you.
In general softening up the connection to the LR in any way, will reduce output from the main things which operate the LR. Your axle is a main connection to the LR. It means soften the connection up and it will be harder to remove weight from the LR. Your problem is probably because the softer axle allowed for some weight to remain on the LR, that needed to be moved. Then when weight needed to go to the LR, some of it that should have left was still there. So in effect, you never got the weight you needed away from the LR and total weight at the LR went back up to what it was prior to entering the corner, too soon. The net of it is all through the corner your kart sat too heavily on the LR.
There are ways to fix it by making the LR work as needed, even though it's retaining more weight through out the corner. But you already have a know fix(installing a thicker walled axle) to try first.
Your only reason to unload weight from the LR is so it can be used when needed, by the RR. It's all a matter of timing correctly when weight leaves and returns to the LR and only moving enough to get the RR to function as needed, at the right time.
You asked about differences and advantages. IMHO, there are no differences and advantages with anything you do setting up. It's all about putting your best guess(factory base line is a good place to start) out on the track and then recognizing and fixing on track problems. Define on track problems how ever you like and it will be a good definition of what needs fixed. Just being over all slow is a well defined on track problem, which can occur for multiple reasons. The same with loose, push, tight and being too free.
Thickness of the axle basically affects how the kart transfers weight, thicker axle reduces flex and thinner axle allows more flex. Putting a thin wall axle on a kart that was designed with a thick wall axle can open up a whole can of worms as far as handling issues, or can allow you to pick up speed, just depends on the chassis and how it uses the left rear i believe. LTG (Todd) would be the one's advice i would be looking for on this subject, or Mike. Both are chassis guru's