I've always heard it's bad for a transmission to tow a load while using overdrive in an automatic or 5th gear in a manual (if it's a 5-speed). My truck is a 5-speed manual and I'll be towing a small boat next week to a lake that's about 4 hours away. The boat is a 15ft aluminum and only weighs a few hundred pounds. Add in a small outboard and some gear and it's still not very heavy. The trailer probably weighs more than the boat. I checked my owner's manual and it says not to use 5th gear while towing, but says this is recommended to maintain engine braking ability. It says nothing about damaging or straining the transmission. My question is, would there be any risk to the tranny if I did use 5th? If it matters, my truck is geared fairly low and turns pretty high RPMs at highway speeds. Really, with two mountain passes each way and lots of back roads, 5th gear wouldn't get used that much if I did choose to use it.