Originally Posted by big-dan
No, they are not the same tag axle in that the early ones (1990-1992 or so) require helper springs on the outside of the shocks to pre-load the shocks in order to get the proper balance between the tag axle wheel and the driving wheels, and without these helper springs, the tag axle wheels will skid when you apply the brakes, even on dry asphalt due to not carrying enough load to prevent them from skidding. It also says that the tag axle is not carrying the load it was designed to carry, thus loading the driving wheels with more than they were designed to carry.
I actually went back and checked on my 2000 Tropical model, and in fact, it was the 1999 F-53 chassis-- looks like the same as HoundDogs. I do remember that it did not have the helper springs.
I also did a weight check in those years, with of all 3 axles when fully loaded, and it was within specs of the manual's/chassis requirements. I know that the shocks made a big difference over the OEM originals and that that 37' coach really had a fairly solid, stable ride in high wind wind, no porpoise-ing, didn't suck you off the road when passing oncoming semi's, etc. I added a SteerSafe to the unit and that I think helped as well.
Adding air assisted components sounds like it would be a great improvement as well.