I can hear a 4L60E saying it's prayers now. lmao.

 

 

Believe it or not the 60e transmissions do fairly well towing as long as you leave them in 3rd, you try keeping it in 4th and youre signing its death warrant.

 

i tow mine in 3rd, its at 65mph and 2200 rpm i think, that good for me.

 

Most of the time the 4L60 doesnt last is because people are worried about their engine @3500 RPM so they drive in 4th instead of 3rd. These engines aren't even at peak power yet @ 3500.
Keep it cool and it will survive, maybe even consider a weight distribution hitch if you haven't already.