I think John Bud and others made some good points when they said your tractor is overpowering the boxblade. You need to look at the parent material thickness and connections to the rear of the box. Their are inexpensive ways to beef up your boxblade by adding some scrap steel in strategic areas to gain performance and thereby weight too. But the stock box has to be built well enough in the first place.
When you start checking out 84" boxes you'll see a significant improvement in material thickness. I have a medium duty 84" Howse that had a very good base structure. The 3pt connection is a solid plate of 3/8 pre-hardened steel that spans from 3pt to the rear of the box. I know it's it's heat treated because I machined it. All the steel is 3/8" minimum with 5/8" bars running to the rear of the box. There scarifier tube is heavy too.
Here is a picture of the stock 84" Howse boxblade. I paid 500 bucks for it 3-1/2 years ago.
When I first got that box for my 55hp tractor I got lucky because I really didn't have a clue as to how heavy duty the boxblade should be. I knew I didn't want to spend 2 grand or more for a boxblade though. It's been through some pretty tough granite, clay roots and rocks. In my case, the scarifier carrier tube was strong enough, but the scarifiers weren't. I bent and snapped several off with that boxblade, so there was no question the box itself was strong enough.
The first thing I did was get some scrap steel and made some supports for the scarifiers. This was not an expensive addition and save on scarifiers. I did the welding myself at my camp. You need to create a generous fillet when doing the final passes.
After that, realizing that I was moving the position of the scarifiers many many times for all the road and ground prep for my new home, I decided to change that too. It was just too time consuming with all I had to do. I made that same boxblade into a gear driven hydraulic model. It's given me years of trouble free work now. I did all the work myself to it and it was a little more expnsive than just adding the supports, but I don't think I have more than 400 bucks into parts total.
Now it's pretty heavy and pretty cool too.
So there ARE some things you can do to fix up a boxblade.
