I've only got #3500 Dexter Torflex axles on my 2019 #7000 GVWR Rockwood 2511S. It does have 14" LR D tires which at the 65 PSI on the sticker exceeds the axle ratings for 2 of them and having probably close to #900 TW.
Just for comparison, my old 2003 #5000 GVWR Prowler had the same #3500 Torflex axles on it, but only the little 13" LR B rated tires which were only good for #2200 each.. I did upgrade to 13" LR D tires, but never had an issue with the Tork-Flex axles..
I'm surprised that a "Grand Design" has leaf spring suspension? Aren't those supposed to be a so called "high end" manufacturer?? From the prices of their units, I would think so??
I don't think my Forest River Rockwood is anywhere close to a "high end" model, and my 2003 Fleetwood Prowler, defiantly was not!
But, they both have had the Torflex as OEM and that's what sold me from the start.
As far as "warranty" work by the deal or the manufacture.. Well, all they are going to do is replace the same part that failed in the first place.. It'll just fail again in most cases..
I think you can go ahead and pay Lawyers to fight a fight that won't go anywhere, or just go ahead with your planned upgrade and start enjoying your rig!
I did have a "warranty" issue with my Rockwood. Fridge would not stay running after it cycled it's temp. I talked to the dealer and they said I'd have to bring it in, they would have to "trouble shoot" the issue, get approval of the warranty claim and just replace the main board of the fridge which is what I told them was the issue...
That would have taken well over a week, plus dropping off the trailer to them (which, they are only 2 miles away, but still a PITA for such an easy fix)
I just bought a new board for $100 and replaced it in about 30 minutes. It was a 2 day online delivery and I didn't have to take the rig to the dealer..
But, that's what worked for me.. Yes, I know they should "pay", but in the end, I have no problem with it, as the hassle of them to pay $100 just was not worth it to me when I am capable of doing the work myself.
Sure, replacing axles is a lot different deal.... I would not take that on myself as a DIY project either...
Just just saying that "warranty" work is not fun at all, no matter what the issue is... :)
Good luck! Mitch