Transmission update / towing !!??

I hear you construct. The short answer is so I don't constantly shift from 6th to 4th and back to 6th every time I crest a slight hill on the highway (with nothing in tow). The 5th and 6th gear ratios, and the current shift points for the gears, don't match the torque curve of the 3.5, when the truck weighs 4400+ pounds.

 

Why does it matter, though? I'm honestly curious. If it bothers you, you can accomplish the same thing by shifting to 4th gear and leaving it there.

A transmission with a lot of gears should be shifting frequently. When you're cruising and cresting hills, it's not trying to match the torque of the engine, nor should it be. When cruising, the engine is trying to maximize fuel economy.

The shift algorithm and points are almost certainly designed with the BSFC (brake specific fuel consumption) map in mind, not just the torque curve. While it's tempting to think that you could know better how and when to shift the transmission, you can't see or feel the things the transmission is optimizing for, like fuel economy.

If the transmission was designed such that 6th gear could be used everywhere, then they would be leaving efficiency on the table for flat-road cruising, which wouldn't make any sense.

 

Your points are reasonable. I am sure low BSFC is the target. However, 4th gear revs the car too high on the freeway, and thus, likely raises BSFC (while trying to make up some lost momentum), so I personally do not like it, as I believe many others do not either. A little more mechanical advantage in 5th would be nice (to stay out of 4th on the freeway when only light on the throttle). Mild gearing can accomplish this (or re-gearing 5th with say a .79 ratio). Holding the high gear while heavily loaded is not good either, as lugging would result, and I am sure BSCF would suffer anyway due to switching out of Atkinson at higher loads. Good discussion construct. It reminds me of my tuning years.

 

First towing with mine yesterday. I know it's a small load, but I didn't even know the trailer with 5 RR ties was back there. ECT on back country hilly roads.

G.

 

I noticed the OP was talking about cruise control. I am pretty sure you should not be towing using cruise control. Also, in my experience, if you engage the ECT button (as you should when towing), my truck has almost never shifted into 6th because it is a tall overdrive gear. It stays in 4th or 5th. The easy solution to your issue is to engage ECT and put it in S5. It will prevent it from shifting into 6th and should give you plenty of power with a responsive throttle. As others have said, you are just going to have to get used to this engine revving higher when more power and torque are needed. The simulated Atkinson cycle at low RPMs will help mileage, but won't put out the same power and torque at low RPMs as the older 4.0 would.

Whoever was talking about how their 2013 would pull a load at a given RPM range is comparing apples to oranges. Different engines, different transmissions, different outcomes.