Coming back from the hunting camp today with my Polaris Ranger on my 6x14 trailer (2000lbs or less), coming up the mountain , 92 degrees outside, I had it in OD and powering up the winding hills no problem, Smarty JR on 70hp setting. I started to slow down up a steep grade then felt a pretty bad shudder, backed off, tranny dropped down a gear, then no further problems. What was it? With the Smarty JR, is it ok to tow on the 70hp setting ( I thought it said tow mode for the 70hp)? I also just got the JR last week, so I am learning. Hope this wasn't an expensive learning experience

 

The tranny has a tow/haul mode for a reason. I would bet you may have gotten the tranny hot. Pull the dipstick and smell the fluid to see if it is burnt.