My wife and I purchased our 13' Scamp this Spring, 2015.  Our tow vehicle is a 2006 Saturn Vue AWD with the 255 hp V-6 with the 5 speed auto. trans (the Honda 3.5 engine and transmission). I installed a transmission cooler and transmission temp. gauge. When we tow the Scamp with the transmission in drive, which is overdrive and 4th gear, on the level the transmission pretty much stays in OD but any incline its shifts to 4th gear and stays their until we are on the level.  At 60 mph, in OD, it runs about 1500 rpm, and in 4th it runs about 2500 rpm.  If I put the transmission in intermediate which is 3rd gear the engine runs about 3500 rpm.  Is there a way to keep the transmission out of OD and stay in 4th?  Is the transmissin being hurt by constant shifting between OD and 4th?  The Vue runs well in 4th at 2500 rpm and tows the trailer with ease.  Any helpful information will be appreciated.

Thanks, Deb and Wayne