Does Rubicon even use 8th gear??

[beaups]

Technically you are correct. The transmission itself does only adapt to its own internal conditions.
However, the entire electronic system, especially the TCM, does adapt to the driver's long term habits.
In today's electronically controlled vehicles, your foot does not tell the engine what it wants like the cable-to-the-carburetor methods of yesteryear. It actually tells the transmission, via the foot pedal potentiometer to the TCM, what it wants. The TCM asks the ECM if it can provide what the TCM wants, and the TCM also asks the drive train if it can handle what's about to come down the pipe. If the answer to all the requests are positive, your foot gets what it asks for. If any answers are negative a series of scenario evaluations ensue, and your foot's request is either granted by some other means, i.e. dropping a gear, or denied altogether.
Like every other computer system, algorithms and the numbers of times they are used are stored in hierarchy form from the most to the least so when you request something of the TCM it starts at the top of the list to grant the request. Habits put the most used algo's at the top of the list. Ergo the system "learns" what the driver wants.
My experience comes from long time use and management of automated class 8 highway equipment. Best way to screw up a new truck .... put a different driver in it every 12 hours.

This still isn't true. The TCM and ECM do not adapt to the "driver's long term habits". The system does not "learn" what the driver wants over any extended period of time. I can't comment on class 8 equipment, but your wrangler isn't profiling you.

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[Howardlv22]

This still isn't true. The TCM and ECM do not adapt to the "driver's long term habits". The system does not "learn" what the driver wants over any extended period of time. I can't comment on class 8 equipment, but your wrangler isn't profiling you.

The Auto trans has adaptive learning..........you drive with a heavy foot, The shift points learn to shift at higher rpm's to adapt too your driving style. You drive with a light foot the shift points will move downward to lower rpms over time.

Pull the trans control module fuse for a minute and re install. (resets the trans to default) Go for a drive with a light foot and see what happens.

Reset trans then Re cal your speedo as well if you upgraded to bigger tires.

This is coming from a ChryslerASE master tech with over 30 years of experience. Believe what you want. I tend to believe the pros. .

this guy beaups is on every thread arguing with everyone. He tried telling a law firm owner/lawyer how the law works.

 

[AnnDee4444]

I agree about this powertrain. I too really like the 3.0. The engine, transmission, and rear axle ratio make it a pleasure to drive. Like you said, it seems perfectly matched for the stock tire size. It’s fun to drive!

Try running through the math once, assuming the rolling radius is half of the 32.8”. That works out to 615 rev/mile at the wheel. My dealer tells me the trans ratio on 8th is 0.64. Is that correct?

The stock K02 specs on tirerack shows that tire to be 635 rev/mile. That must be at rated load and pressure I imagine.

Anyway, using those two rev/mile figures, I come up with between 1590 and 1642 engine rpm @65. My tach indicates somewhere around 1600 at that speed (with stock K02), so I had concluded the 0.64 8th ratio may be correct. But I don’t know how accurate my tach reads of course.

Maybe our tachs read a couple hundred rpm different.

In the non-Winter months, I run 315/70/17 K02, which runs a bit less than the 35” I stated. With those, my tach shows 1500 @60.

You might find some interest in this post. The K02's rolling diameter is between 96.8%-97.3% of the calculated diameter.

You can differ all you want, but you’re still wrong. The ZF8 adapts to itself - clutch wear levels, fluid viscosity, etc. it does not adapt to it’s drivers’ long term habits.

Do you have any other technical information about this?

 

[txj2go]

I would expect the 8-spd Rubicon with stock tires to easily get to 8th gear on the highway.

I have a 2018 V6 auto JLU Sport that I recently added Rubicon takeoff tires to. A month ago I did an 1800 mile road trip, much of which was on highways with 75mph speed limit. Under ideal conditions it would hit 8th gear, but just a tiny bit of uphill or a tiny bit of headwind or a little sidewind and it would drop to 7th gear. I calculated that the speedo should be off by 2-3 mph at highway speeds so I was typically driving at 73mph indicated on the speedo. 7th gear would be around 2200rpm, 8th gear would be around 1800rpm. On the trip out there was a lot of headwind so rarely hit 8th gear. I averaged 20mpg on the entire trip, calculated by the amount of gasoline bought and the actual distance driven, not the odometer distance or the in-car pcm.

 

[beaups]

You might find some interest in this post. The K02's rolling diameter is between 96.8%-97.3% of the calculated diameter.

Do you have any other technical information about this?

There's a lot of documentation out there about what the transmission adaptations do (learn their wear levels etc) but not much about what they don't do (build some profile on the driver). A quick google turned up this, though. It gives some good details on what the ZF8 *is* "learning", how to properly reset the adaptations etc. The first paragraph is a good summary:

"The 845RE, 8HP45, or the 8HP70 8-Speed Automatic Transmission uses a sophisticated shift algorithm that includes learned information so that the shift quality remains excellent even as the transmission wears. This learned information is recorded in memory cells referred to “Adaptation Memory Cells”. Each applied clutch records the amount of time it takes to fill the clutch (Fast Filling Counter/Filling Time) and the amount of pressure (Filling Counter/Filling Pressure). The adaptation memory cells are set to zero (0) on every new transmission (new in vehicle and/or replaced for service) and when the transmission control module is replaced for service. In addition, the adaptation memory cells are set to zero (0) when the transmission control module adaptation memory cells are cleared using the wiTECH diagnostic scan tool. Until the adaptation has been learned/relearned, the transmission shift quality may not meet the customers expectations."



http://www.wk2jeeps.com/tsb/tsb_wk2_2101214.pdf

 

[Yogi]

This still isn't true. The TCM and ECM do not adapt to the "driver's long term habits". The system does not "learn" what the driver wants over any extended period of time. I can't comment on class 8 equipment, but your wrangler isn't profiling you.

Profiling ... LOL ... that is such a cool term, and so appropriate. I never thought of it that way, but, like it or not, that is exactly what it is doing.

I drive on mostly flat ground, yet I rarely see 8th gear much lower than 3k on the tach. The simple reason is that I have a heavy foot, and that's where she sees me shifting to 8th.
The solution is relatively simple ... a reboot of the system. Cut all the power to the system for 10 minutes or so, and it's back to factory. But, I like it the way it is, so I leave it alone.

The basic AI algorithms in a Freightliner Cascadia are no different than those in a Ford F-150, or a Chevy Camaro, or a Jeep Wrangler ... or an Echo Dot for that matter.
It's fundamental AI, and your vehicle does learn "you" to an extent. Open up your outbound email, and hit the drop down list in the "To:" field. Who's name comes up? The person you email the most

Some people are kind of freaked out by this "AI", some not so much. I'm in the "not so much" camp. Regardless, for better or worse, it's the future.

 

[beaups]

Profiling ... LOL ... that is such a cool term, and so appropriate. I never thought of it that way, but, like it or not, that is exactly what it is doing.

I drive on mostly flat ground, yet I rarely see 8th gear much lower than 3k on the tach. The simple reason is that I have a heavy foot, and that's where she sees me shifting to 8th.
The solution is relatively simple ... a reboot of the system. Cut all the power to the system for 10 minutes or so, and it's back to factory. But, I like it the way it is, so I leave it alone.

The basic AI algorithms in a Freightliner Cascadia are no different than those in a Ford F-150, or a Chevy Camaro, or a Jeep Wrangler ... or an Echo Dot for that matter.
It's fundamental AI, and your vehicle does learn "you" to an extent. Open up your outbound email, and hit the drop down list in the "To:" field. Who's name comes up? The person you email the most

Some people are kind of freaked out by this "AI", some not so much. I'm in the "not so much" camp. Regardless, for better or worse, it's the future.

AI is great stuff indeed. It just isn’t in your wrangler transmission, no matter how bad you want it to be. Read the adaptation doc I posted earlier in the thread. I suppose it’s possible you are triggering the transmission to relearn it’s adaptations which would cause it to want to use each gear. But it’s still only learning about itself, not you.

 

[txj2go]

What I'm wondering is- if you put it into manual mode can you force it to use 8th gear in situations where it doesn't want to?

 

[Overland Productions]

I have the 3.0 L diesel. If I am above 56 mph at constant speed and if the grade is <6%, I am in 8th, at 1,850 rpm.

Likewise.

samesies

 

[Hound Dog]

What I'm wondering is- if you put it into manual mode can you force it to use 8th gear in situations where it doesn't want to?

Nope. The manual setting limits the top end. It will still downshift to keep you from forgetting and bogging down the drivetrain.

 

[00 Trans Ram]

Remembering this thread, I looked at mine today. Stock JL Sport with diesel. It shifts to 8th at 50mph under the barest of acceleration, and keeps it in 8th until 45mph, when it will drop back to 7th.

 

[mwilk012]

What I'm wondering is- if you put it into manual mode can you force it to use 8th gear in situations where it doesn't want to?

yes, you will just have a very weak pedal response and poor fuel mileage.

 

[mwilk012]

Nope. The manual setting limits the top end. It will still downshift to keep you from forgetting and bogging down the drivetrain.

you can shift it into 8th manually and it will remain there within reason.

 

[Jeepsmashin]

I use 8th gear manually to save gas and use cruise control at the same time when driving on the freeway. Or else sometimes it'll shift down to 7th when slowing down or going up a hill.

 

[Yogi]

AI is great stuff indeed. It just isn’t in your wrangler transmission, no matter how bad you want it to be. Read the adaptation doc I posted earlier in the thread. I suppose it’s possible you are triggering the transmission to relearn it’s adaptations which would cause it to want to use each gear. But it’s still only learning about itself, not you.

"But it’s still only learning about itself, not you." ... yes, you are correct ... that is a much more appropriate description.
I saw your adaptation document ... great find, good info.

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