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  #13  
Old 10-04-2014, 10:59 AM
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9 speed transmission?

It's somewhat comforting that it's not necessarily the hardware that's causing the problem, but the software. The latter you can gradually improve, the former sometimes not at all.

Keep us posted & good luck!


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Old 10-04-2014, 12:42 PM
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Re: 9 speed transmission?

Quote:
Originally Posted by blk14altitude View Post
I also noticed something weird going down a hill doing 35 mph, the tranny downshifted and the tach went up to almost 3500 rpm until I hit the bottom of the hill and then it upshifted and the tach went back down.
Sorry for the brevity with "Rev Match". Was on a trip and checked in with my phone and didn't have much time. There's an article on ZF's 9 speed, maybe you've seen it. ZF's 9-Speed 9HP Transmission Puts Dog Clutches On The Leash | The Truth About Cars

It explains the dog clutches used and why the computer needs to synchronize the engine with the transmission (rev match) before engaging these clutches between 4-5 or 5-4 and 7-8 or 8-7.

I don't drive a lot of different cars but I drove my son's Infinity with paddle shifters and on downshift its computer did the same rev match. But that drivetrain did seem to provide more engine braking than the Cherokee does after the shift.

Not sure this is relevant to your description but I thought I'd share the article anyway.
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Old 10-04-2014, 07:19 PM
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Re: 9 speed transmission?

@DesertHiker do you have a link to TSB#21-013-13?
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Old 10-04-2014, 07:33 PM
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Re: 9 speed transmission?

Quote:
Originally Posted by Array View Post
Sorry for the brevity with "Rev Match". Was on a trip and checked in with my phone and didn't have much time. There's an article on ZF's 9 speed, maybe you've seen it. ZF's 9-Speed 9HP Transmission Puts Dog Clutches On The Leash | The Truth About Cars

It explains the dog clutches used and why the computer needs to synchronize the engine with the transmission (rev match) before engaging these clutches between 4-5 or 5-4 and 7-8 or 8-7.

I don't drive a lot of different cars but I drove my son's Infinity with paddle shifters and on downshift its computer did the same rev match. But that drivetrain did seem to provide more engine braking than the Cherokee does after the shift.

Not sure this is relevant to your description but I thought I'd share the article anyway.
Good article... I was puzzled at the lack of engine braking on downshifts; now it all makes sense.
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Old 10-04-2014, 08:30 PM
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Re: 9 speed transmission?

Quote:
Originally Posted by Array View Post
Sorry for the brevity with "Rev Match". Was on a trip and checked in with my phone and didn't have much time. There's an article on ZF's 9 speed, maybe you've seen it. ZF's 9-Speed 9HP Transmission Puts Dog Clutches On The Leash | The Truth About Cars

It explains the dog clutches used and why the computer needs to synchronize the engine with the transmission (rev match) before engaging these clutches between 4-5 or 5-4 and 7-8 or 8-7.

I don't drive a lot of different cars but I drove my son's Infinity with paddle shifters and on downshift its computer did the same rev match. But that drivetrain did seem to provide more engine braking than the Cherokee does after the shift.

Not sure this is relevant to your description but I thought I'd share the article anyway.

The linked article is a fascinating read. Thanks for that!

Honestly, when I was test-driving a '15 TH I had absolutely no complaints, and I spent good 60 minutes testing it on a highway.

I'm excited to finally get hold of mine.


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Old 10-05-2014, 12:27 PM
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Re: 9 speed transmission?

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Originally Posted by rpasetto View Post
@DesertHiker do you have a link to TSB#21-013-13?
Not sure exactly where I found it, but no doubt a Gooooooooooooogle search. If you can't find it, then send me a PM with your email address, and I'll forward the related TSB PDFs that I have.

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Old 10-05-2014, 02:06 PM
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Re: 9 speed transmission?

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Originally Posted by Desert Hiker View Post
Not sure exactly where I found it, but no doubt a Gooooooooooooogle search. If you can't find it, then send me a PM with your email address, and I'll forward the related TSB PDFs that I have.

Desert Hiker
Heres all the tsb for the cherokee.

http://www.jeepgarage.org/f76/tsb-an...kee-71873.html

http://www.wk2jeeps.com/Misc/Cheroke..._21_013_13.pdf
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Old 10-05-2014, 09:22 PM
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Smile Re: 9 speed transmission?

Gang,

This is a great thread with some interesting and factual information, as opposed to "impressions", or "personal opinions" (not that there is anything wrong with those).

Based on my impromptu research it appears that the 9 speed tranny has been created with two key factors in mind: (1) fuel consumption, (2) versatility

Both fully justify the coupled clutch system, and this kind of setup has been used before with relatively good success rates. The potential problem from the hardware standpoint appears to be the form factor; the compact size & dimensions cause some concerns for heat dissipation. Only time can tell how reliable the unit is, and if the concerns are warranted, or not. Personally, I am giving it a benefit of a doubt, for now.

Throughout 2014 Chrysler (Jeep) responded rather aggressively through its dealerships by replacing whole units, regardless if a hardware, or software was to be blamed. The vehicle had just been introduced, and it was considered crucial for brand's well-being in the CUV market. Fast-forward to 2015, we now have vehicles with vastly improved software controllers, and the usual fix is to patch a previous software iteration. If that proves to be the only necessary solution, I will have no problem with living with it; think about this scenario for a second: a few months ago one of passenger's window switches stopped working in my '11 Altima. I reported the fact to the dealership with relative dismay expecting a mechanical failure. Long & behold, two hours later, I got my car back with a note that no hardware fixes were necessary, and it was just software that needed the upgrade (the dealership provided my with an acquire bulletin copy for my review, so no BS).

My take is this: let's all cool down & chill out. Let us run those vehicles for a year, or so and click as many miles/kms as possible with variety of experiences and dynamics. We'll see how well the tranny learns, how it up- & downshifts in different shift configurations triggered by real-life situations.

Myself, I am cautiously optimistic, especially after familiarizing myself with the aforementioned article by the Truth About Cars.

Thanks for sharing all your stories. This what has made the whole thread a very inspiring one to read.

Cheers!
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Old 10-05-2014, 11:19 PM
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Re: 9 speed transmission?

@m_iOS_dev - I agree with your assessment.

I have an impression and that's all it is because I am no expert. It's based on 750 impressive miles in my 2015 Cherokee. The entire drivetrain has performed well so far. I realize this could change drastically in the near or distant future.

The drivetrain's break-in may be more important than usual and the transmission's form factor, as you stated, could be key. I have been taking the following precautions based on comments in two Cherokee forums:

1) Order and do not allow the vehicle to be used in test drives
2) Follow the break-in procedure closely
3) Give it a rest now and then during break-in to allow for heat dissipation
3) Keep an eye on the transmission fluid temperature during break-in and reduce speed when it gets over 165-170 degrees

However, there may be other systems contributing to drivetrain issues such as the Electronic Stability Control/Traction Control Systems. It's possible the transmission isn't causing some of drivetrain issues being reported.
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  #22  
Old 10-06-2014, 08:02 AM
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Re: 9 speed transmission?

Well from what I can remember it took me a couple thousand miles to achieve 8th. It was at that point that my mpg's improved rapidly on the highway.
It all seems to be tied to the AL process.
9th started showing up at around 3,000 miles. 9th would only show up for me at 74mph on a slight downgrade with my foot off the gas. But I did see it a couple of times, thus I know it does work.
The TCM will only allow the most optimal gear, based on conditions and speed to maximize mpg, so it seems.
If some one is not achieving 8th at 65mph or over a talk with the dealer is in order.
Check to see if all the TSBs have been done. Mine goes into 8th between 60-65mph.
Under that its in 7th.
Also you can set the highest gear at 9th or even 8th, but if the TCM does not deem that gear appropriate it will not use it.
It would be nice if the Cherokee had a manual mode but it does not.
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Old 10-06-2014, 08:13 AM
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Re: 9 speed transmission?

Coming from 2 srt8 this cherokee tranny is way diff in its own way. I am finding out a lot of things just in testing. Yesterday i was in DRIVE and put it in manual mode and it was in 5th gear and slowed up to see if it would down shift into a lower gear my its self with out me moving the lever and it did. From what i have seen the tranny will not let you lug the motor no mater if its in drive or manual mode. Now another time i was on freeway and was coming to a incline so i put it in manual mode to see if it would down shift and it didnt so i down shifted my self BUT i may of not let it lug down the motor enough as i was on the freeway. Now even on my 2012 srt8 there was a big diff in shifting in auto and sports mode and the wife liked the sports mode for shifting but auto mode for the ride. I no 1 thing ill be using sports mode at the track lol.
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Old 10-06-2014, 08:34 AM
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Re: 9 speed transmission?

Quote:
Originally Posted by Array View Post
@m_iOS_dev - I agree with your assessment.

I have an impression and that's all it is because I am no expert. It's based on 750 impressive miles in my 2015 Cherokee. The entire drivetrain has performed well so far. I realize this could change drastically in the near or distant future.

The drivetrain's break-in may be more important than usual and the transmission's form factor, as you stated, could be key. I have been taking the following precautions based on comments in two Cherokee forums:

1) Order and do not allow the vehicle to be used in test drives
2) Follow the break-in procedure closely
3) Give it a rest now and then during break-in to allow for heat dissipation
3) Keep an eye on the transmission fluid temperature during break-in and reduce speed when it gets over 165-170 degrees

However, there may be other systems contributing to drivetrain issues such as the Electronic Stability Control/Traction Control Systems. It's possible the transmission isn't causing some of drivetrain issues being reported.
X2
Finally some one else that understands the importance of the break in proceedure. It may be only 300 miles but even more critical than ever.
Overheating the fluid/gears might be all it takes to cause problems down the road. Open that baby up at 200 miles and that could be all it takes.

Another point to back your point up is the trailer tow break in! Thats 500 miles not exceeding 50mph! Thats an entirly seperate break in proceedure. Thats for a reason, tempering those gears as not to overheat them and the fluid. All the gears including differential.
The differencial on a true 4x4 will keep the axle tracking properly, that is allow the wheels to turn at different rates without skipping/wobbling.
You would see that a lot years ago on 4x4's that could only be driven in that mode on slippery surface. If driven on dry pavement damage would follow.
What I think a lot do not understand is the transmission is sealed! Thus if the fluid burns a bit from overheating there is no easy way to check it. Thus ignoring a problem that will cause problems down the road. That is why there is no such thing as lifetime fluid except maybe the Sunday driver.

Yours will be fine! Software updates have resolved most of the AL issues for 2015's.
Mine was a 12/11 build. Never needed the TSB's and everything is working perfect to date. I did take it easy for the first 1,000 miles till most of the AL was done. Could not be happier with this vehicle. Getting 32-33 on the highway at 70mph is a huge bonus.
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