Okay I have read about the overdrive off and on, and if the transmission start hunting have the tow/haul on, etc. I was also told to keep towing with the tow/haul light off but the key for it is to keep your rpm over 1700. Well that is my problem, when I towed the last time with my overdrive on (tow-haul light off), my rpms at 60 mph went down between 900 and 1100. Is that means that I do not have a choice but to tow with the tow/haul on. With the tow/haul light on my rpms were from 1900 to 2100rpms. Sorry but I am confused.

 

When you are in OD and let up on the throttle, the torque converter will unlock and the engine wil drop as you are coasting. If you hit the fuel again, the rpm will rise and the TC will lock up again.

If your are in tow/haul (OD off) you will be in 3rd and the TC stays in lockup when you let off the fuel pedal. This helps hold the speed constant when you are going down grades, keeps the engine rpm up.

Something is wrong with the rpm and speeds you are quoting. With 4.1 gears, OD should be about 2000 rpm at 65 mph and about 1700 rpm at 55 mph. Third gear with 4.1 gears should be about 2500 rpm at 55 mph.

Keeping the rpm above 1700 in OD means when you are applying fuel and working, not coasting. For your case with 4.1 gears, only use OD if you are over 55 mph and it is not dropping out of lockup on grades or with headwinds. If it drops out of lockup (rpm goes up but is not actually shifting to 3rd) shift into tow/haul.

 

If I tow on a relatively flat stretch of highway, I tow in overdrive, unless there is a HEAVY wind. I do not switch out of OD unless my truck starts to lug. If I'm on the flats and my RPM are 1100, great! I can still tap the throttle, and my truck will accelerate just fine. But, if I'm going into a STRONG wind I feel my truck start to lug,I might have to start giving it a lot of extra throttle because of a 40mph wind, that means I'm lugging the engine. Or if it is really strong, it might even switch out of OD on its own, which means it was really lugging, and I should have been out of OD. Same rule applies for me on the hills. If I'm going up a hill and hardly slowing down, I stay in OD. If I have to keep giving it extra throttle, and its not really taking off, I'm probably lugging. The engine even sounds different when your lugging (more "sucked- out"?). I don't know how else to describe it, but you are right that if you always try to keep the RPM's way up, then you would never tow in OD, unless you're doing 70mph+ with your trailer. Mind you- I have the 3.73's.

 

Rule of thumb......use Overdrive unless the engine starts lugging or the transmission starts hunting. If it does that, push the little button until you are in a situation that allows you to get back into overdirve.

I live by that and it seems to do very well. I usually only have to switch out of overdirve while climbing mountain passes or a StupidDookie is in front of me making me slow down!