Manual mode to stay in a highway gear

[wuykats]

Wow, just finished reading through the 19 page transmission thread re fluid change. Lots of information in there. One thing that was mentioned is transmissios "hunting" gears at certain speeds. My Gladiator seems to not know exactly what gear to be in on certain stretchs of roads. Usually shifts out of 6th into 7th at 60 to 65 mph on the way to work, then may shift to 8th. Same speeds, same road on the way to work. If you put the trans in Manual mode you can shift to 8th, and it will hold there fine, generally mpg is better in 7th or 8th than in 6th. I am sure the computer is communicationg between the engine and trans, I just don't know the parameters of what that communication entails. I am reasonably sure the computer doesn't want to put the engine in a "lugging" situation, so it downshifts accordingly. And I would think the engine would be happiest operating well into its torque range. With that being said, am I prolonging the life of the powertrain by manually going into 8th and avoiding the 2 to 3 downshifts/upshifts that it performs on a flat 5 mile long highway stretch?

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[VA6489]

What kind of modification do you have on your rig?

Big Tires on stock gearing is what it sounds like. Did you reset the tire size in the computer?

Did you up size tires and not change gears?

 

[Zachanadandy]

7th is still overdrive. 6th is 1-1. All 3 are highway gears. These aren't wide ratio 3-4 speeds from the 80s. They are designed to shift a lot. The 3.6L doesn’t make peak torque until 4k rpms. You don't need peak torque to cruise along with a tailwind. Conversely a nice headwind pushing against this brick on wheels may need 7th or even 6th dead flat. It's not hunting gears, it's doing what a double overdrive automatic is supposed to do.

 

[Badunit]

If it holds 8th when you do it, whatever works for you. It is hard to believe it would hurt the transmission, the engine torque is low at the lower RPMs. The downside, though, and it is a big one, is when it finally determines you are lugging it too much it will downshift on its own, several gears worth, as deep as if you floored it at that speed (which is what it sees you doing). It will NOT shift back up automatically and it will be screaming at high RPMs until you either put it back in Auto or upshift it a few times yourself.

"Manual" is not manual, it is some weird semi-automatic mode. Personally I would prefer that it limited the top gear and shifted the rest normally, like when you want to shut out 8th gear to prevent hunting or want to keep it in a lower gear for more spirited driving up a mountain road. Being true "manual" would be okay, too, but people (including me) would forget to downshift and would be in too high a gear after slowing down or starting from a stop. It would have to be "manual" all the time.

 

[Alpine Warthog]

Mine seems to LOVE 4th gear, It will stay in 4th into 60 mph if there is anything near an uphill or headwind. I did go to 35s with stock gears, and did tazer to adjust tire size. I wonder if it forgot the new settings after a while?

 

[JTdiRtyD]

"Manual" is not manual, it is some weird semi-automatic mode. Personally I would prefer that it limited the top gear and shifted the rest normally, like when you want to shut out 8th gear to prevent hunting or want to keep it in a lower gear for more spirited driving up a mountain road. Being true "manual" would be okay, too, but people (including me) would forget to downshift and would be in too high a gear after slowing down or starting from a stop. It would have to be "manual" all the time.

IMO manual mode operates as it should, the driver controls the shifting UNLESS rpm's are too high for "x" amount of time, in which case it will upshift automatically to prevent damage.

My Tacomas manual mode was the gear limiting type, it drove me crazy. It was nice in some cases, but overall it annoyed the hell out of me because it would still shift when I didn't want it to. But then again, the 3rd gen Taco transmission is known to be hot garbage and unpredictable, and one of the main reasons I traded it in.

 

[Mr Miami]

Wow, just finished reading through the 19 page transmission thread re fluid change. Lots of information in there. One thing that was mentioned is transmissios "hunting" gears at certain speeds. My Gladiator seems to not know exactly what gear to be in on certain stretchs of roads. Usually shifts out of 6th into 7th at 60 to 65 mph on the way to work, then may shift to 8th. Same speeds, same road on the way to work. If you put the trans in Manual mode you can shift to 8th, and it will hold there fine, generally mpg is better in 7th or 8th than in 6th. I am sure the computer is communicationg between the engine and trans, I just don't know the parameters of what that communication entails. I am reasonably sure the computer doesn't want to put the engine in a "lugging" situation, so it downshifts accordingly. And I would think the engine would be happiest operating well into its torque range. With that being said, am I prolonging the life of the powertrain by manually going into 8th and avoiding the 2 to 3 downshifts/upshifts that it performs on a flat 5 mile long highway stretch?

I personally would not be overly concerned about the shifting thing in automatics. Remember, these things are designed to shift, and shift a lot. Think about the 10 speed trans that they use in the Ranger and I'm sure other many other Fords. In the case of the Stellantis 8 speed (ZF) transmissions, these are designed for squeezing the last mile (or kilometer) out of every gallon (or liter) of fuel. That is the reason auto transmissions today get as good fuel mileage as manual boxes. The computer is telling it when to shift to achieve the best results at any point in time based upon load, speed and a number of other factors. The computers are calculating these variables many times per second.

In theory, the manual should surpass the automatic due to less inherent losses of torque and the heat produced that occur with a "fluid driven" automatic as opposed to the direct metal on metal gearing of a manual. However, computers in an automatic are constantly controlling it which is simply not practical, or possible, with a manual. You would be constantly using the clutch to change to the optimum gear.

Remember, the automatics today are much different from the automatics of the past.

 

[Sandman 4x4]

I use manual mode on the highway most of the time with the ACC engaged, that has increased the life time average mileage over the last 2,000 miles to 20.1 mpg. I have noticed that when I’m in man mode in top gear, if I roll in the throttle or punch over 1/2 the transmission will drop to 6 th and stay there. Then I move to the right to auto, or down to upshift. I’ve also discovered in manual mode from a red light dead stop you can start off in 2nd very smoothly and feathering the gas pedal and upshift at 2,100 rpm’s is nice and smooth, especially in rain, where in automatic mode if I give too much I will spin the tires way too easily.

 

[Zachanadandy]

Upshifting at 2100rpms is the definition of lugging the pentastar. It's terrible for the engine, the oil pump never even gets in to high lift mode, and the pentastar isn't making any power at that point. You do you, but don't be surprised if your engine doesn't live a long life like that.

 

[Mr Miami]

Upshifting at 2100rpms is the definition of lugging the pentastar. It's terrible for the engine, the oil pump never even gets in to high lift mode, and the pentastar isn't making any power at that point. You do you, but don't be surprised if your engine doesn't live a long life like that.

But look at the bright side, you would probably gets better gas mileage while it lasts.

 

[Zachanadandy]

But look at the bright side, you would probably gets better gas mileage while it lasts.

2 mpg for 50k miles won't pay for a new engine even at ridiculous CA gas prices...

 

[Mr Miami]

2 mpg for 50k miles won't pay for a new engine even at ridiculous CA gas prices...

But you aren't factoring in the potential savings of turning off the vehicle when going downhill (provided you are going in a straight line and don't have to make a turn).

 

[wuykats]

What kind of modification do you have on your rig?

Big Tires on stock gearing is what it sounds like. Did you reset the tire size in the computer?

Did you up size tires and not change gears?

11.50 X 35's, so yes I upsized the tires and yes, used the tazer to reset the size.

 

[NC_Overland]

When mine shifts out of 8th, it’s because it needs more power. As previously mentioned, it’s a double over drive. When I tried that “trick” years ago and it was useless. If you shift back to 8th you can floor the gas and it won’t accelerate or sometimes even maintain speed. 7th gear is only about 500 RPM higher than 8th so I don’t sweat it.

 

[gearhead22]

Manual mode just locks you in the gear. You can notice at times you’ll actually lose speed while doing it. The engine just doesn’t make the power to adequately pull 8th gear when head winds or hills are involved. The transmissions are designed to shift and I’d argue with 8 speeds, they intend it to do it frequently hence why there’s 2 overdrives.

Personally I feel the programming of the transmission is lack luster. For instance it wants to downshift too easily. Many times there’s just a slight hump in the road or similar that it can easily hold the gear it’s in if it would be willing to just drop 1-2 mph. For example 70 going to 68-69. But it’s as if Jeep programmed it to not lose any speed prior to a downshift. Many other vehicles will hold for a second, for example cruise set at 70 it’ll drop to 68 before downshifting. At least my experience with my jeep is if I’m set at 70, it refuses to be any lower than that.

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