I tow with my 5sp wd21 all the time! I do worry about being too hard on the tranny. My utility trailer weighs about 600lbs empty, and it's never empty! I live/play/work at 7000ft with lots of hills. Your truck will pull more than it should, just not too fast! If you can be patient in traffic you'll be just fine. If not sell me your rig and get something bigger! Best of luck!!