I owned a 2006 Gearbox 375FS, a 39' toy hauler. It pulled well, it handled well, and it performed as described. I had issues, but they were my fault, forgot to hit the low point drains and had some frozen fixtures.
The other issue was walking in one day after it sat for a month, I saw light at the rear, around the door. I went outside and the door was latched and locked. Then I looked at the sides. The metal frame around the ramp door was coming away from the side wall. I took mine to a RV dealer here in Tucson, and they fixed it for $100. Great job, great price, and it was done very professionally.
I was a RV tech, but for $100, it was an easy decision to let them do it. They drilled thru the door frame, and put some lag bolts into the side wall, from the rear to the front, and put a cap over the hole they drilled in the frame. Cactus Auto and RV Sales is the dealer that did it.
No other problems with the one I had. And that door issue is a design flaw. You will have a lot of fun with it, if you get it. We had ATC 70's and a 4 seat 14' sand car in ours.
Tank Thomas, USAF Ret.
There are no secrets to success. It's the result of preparation, hard work and learning from mistakes.