[uhftx]

If your grand design towed perfectly and the Montana does not. With zero changes in your tow vehicle then it is a weight and balance issue with your RV. We can not make suggestions other than try towing with a tank full forward of the axles of the Trailer. If your fresh water or other tanks are behind the axles of the Monty. Make sure they are empty. One tractor trailer and single end pickup. You never know how that trailer is loaded and should not make a difference how the trailer is loaded so long as the load is secure. There is something wrong with your set up for sure. Lots of trial and error, your analysis will solve the issue, with persistance.