Reddit mentions of Hayden Automotive 392 Transmission Line Fitting Kit

I believe the 5000 lb. number is when you have the aux. Transmission cooler and a weight distributing hitch. You shouldn't need a weight distributing hitch when only towing 1700 lbs, but it sounds like you need a cooler for sure.

I'm not familiar with the KK at all, but when I did the install on my ZJ, I didn't need do take the radiator or condensor our like someone else commented about. I did take off the bumper and grill though. I just spliced into the rubber transmission lines with double barbed brass fittings with 2 fuel injector clamps on both ends, and ran new 3/8" high temp trans line in front of the radiator and mounted the cooler to the supports behind the grill. The fuel injector clamps are important, because the dont cut into the rubber lines linke the traditional screw type hose clamps.

Another thing you need to think about is if you want to isolate your aux. cooler from the in-radiator cooler you already have. Most factory Aux. cooler setups are plumbed in-line with the in-radiator cooler. I just completely took the in radiator cooler out of the equation and got an oversized cooler. It a lot easier to not have mess with the fittings on the radiator, since they always seem to be a pain and usually require special tools. It will make your engine run a tick cooler as well. Some people think that you need the in radiator cooler to "warm up" the transmission fluid in the winter, but I've had mine separated for years and I've driven in temperatures as cold as -17*. It took longer until it would shift into overdrive, but that seemed to be the only issue. I'm also not sure it actually warms the fluid up any faster because on initial cold start up the thermostat is closed, so the coolant in the radiator isn't circulating around the engine, so that coolant is just as cold as everything else.

By isolating the aux. cooler, you can also avoid the dreaded "strawberry milkshake", where the radiator cracks/leaks internally and your transmission fluid and coolant mix and gets pumped through the transmission creating a pink frothy goop, that will probably take out your transmission. Thats super rare, but it does happen, Xterras were known for that problem.