ROYBUCK.....Your current coach has a single axle and it's set at a pretty standard distance from the rear of the coach, as are all DP's. The 45' will have a tag axle, pushing the drive axle forward at least 36". So if a single axle DP has for example, six feet of coach behind the rear axle, the tag axle DP will have nine feet of coach from the rear drive axle (pivot point).
So.....you'll gain a little overhang to watch for and will have to make sure you drive a feet few farther forward before making turns. We just went from a 36' to a 40'. It was only a 3' difference since the 36' was actually 37'. It wasn't a huge difference, but I find I have to pay attention making tight turns until I get use to the new length. We had the 36' for 10 years.
The good news.....our new coach has a 60 degree front wheel cut and the wheelbase is the same as our 36' since the drive axle is pushed forward for the tag. We can now turn sharper in our 40' than we can cold in our 36', but have the ride of a longer coach.
Don & Mary
2019 Newmar Dutch Star 4018 - All Electric
2019 Ford Raptor Crew Cab