[Array]

I'm lucky enough to have access to any technical information from any car manufacturer from work. ....

Excellent! This could be a gold mine of information. We have a lot of information on the hardware involved in the drive train. Here are some of the patents I found that describe the hardware:

http://jeepcherokeeclub.com/4-2014-jeep-cherokee-general-discussion/29978-selec-terrain-mode-power-distribution-8.html#post1946649

http://jeepcherokeeclub.com/33-engine-technical-discussion/173369-torque-split-uncovered.html#post1963153

http://jeepcherokeeclub.com/33-engine-technical-discussion/146353-ad1-ad2-adl-uncovered.html#post1617785

However, haven't found anything about the software control other than the Jeep videos on the AD1, AD2, and ADL systems; and those are not very revealing.

Is there any other information on the KL 4x4 drive trains you can share?

 

[Cherokeehawk]

Is there any other information on the KL 4x4 drive trains you can share?

Possibly, I didn't really dig to deep when looking at the various descriptions of the drive train before. I'll take a closer look this week.

 

[CoolhawkJeff]

Same Issue

I have 2015 TH. Same issue, binding when turning, otherwise no noticable issue. Dropping off at dealership next week for warranty repair.

 

[CoolhawkJeff]

So the dealership says the differential is damaged due to 2/32s difference in tire wear front to back. Does this seem reasonable?

 

[Fj4080]

All most sounds like the tires were never rotated.

 

[CoolhawkJeff]

I think it is an off-lease vehicle and ill bet you are correct. What surprises me is that if it is that sensitive to tire wear, every off-lease Jeep should have a similar problem logic saying leasees don't other with maintenance? The tires "look" of but measure 5/32 different Carsense warranties engines for life(300k) to offset the risk of a poorly maintained leased vehicle engines but not the drivetrain.

 

[.127690]

Never heard of a diff going bad because of tires not being rotated.

Sent from my SM-G930W8 using Tapatalk

 

[Desoto]

Not buying this one at all. Any variance in tire diameter outside mfg. specs will throw an ABS code and possibly other traction related faults. We do not rotate tires at all, just slap on as needed. Never a problem. If someone installs the wrong size tire, it will show up immediately with an ABS warning light and the offending sensor.
Ask the Dealer to detail the diagnostics involved in this decision or find another.

 

[Mark_]

Not buying this one at all. Any variance in tire diameter outside mfg. specs will throw an ABS code and possibly other traction related faults. We do not rotate tires at all, just slap on as needed. Never a problem. If someone installs the wrong size tire, it will show up immediately with an ABS warning light and the offending sensor.
Ask the Dealer to detail the diagnostics involved in this decision or find another.

I remember someone here bought a new KL that came - off the lot - with one mismatched tire (225/60 instead of 225/65 IIRC) and there was a 4WD not available message in EVIC. 2/32 does not sound like a lot to me, for sure.

Great idea to ask for details on this diagnosis. Maybe get @JeepCares involved too.

 

[.127690]

They are full of it. If it was me I would have started to laugh at them.

Sent from my SM-G930W8 using Tapatalk

 

[Fj4080]

Not buying this one at all. Any variance in tire diameter outside mfg. specs will throw an ABS code and possibly other traction related faults. We do not rotate tires at all, just slap on as needed. Never a problem. If someone installs the wrong size tire, it will show up immediately with an ABS warning light and the offending sensor.
Ask the Dealer to detail the diagnostics involved in this decision or find another.

As you run a taxi service and have way more experience than me with the Jeeps it very well could be. But I have ran into this problem in the past, of course, it was in the 90's and different tech then now. Still, in an AWD system, it would seem this would be problem-matic in a tight turning situation. With that said I know all too well the stealerships will feed you a line of crap when they don't know what is wrong AKA ESS. @Desoto is right that you should push them for more info.

 

[Desoto]

Other Mfg. are more susceptible to a small changes in revolutions per second than FCA. Ford being the worst. Having to replace an entire set of tires at 30k when only 1 tire failed is a tough pill to swallow. Even with the wrong size tire installed, I have never experienced a chatter on the KL.

 

[CoolhawkJeff]

I think they are laughing as they have my money... Used car superstore won't yet honor the warranty they included with purchase as Jeep refuses to fix under warranty. Cherokee sits at Jeep dealer while they battle it out. 3 weeks after realizing something is wrong and into second week after drop off, no car, no part replacement and a diagnosis of bad differential.

On the cusp of getting loud at the dealer and making a scene, not good for anyone....

 

[AP2019]

Don't want to keep a multi year thread going, but I looked for definitive answers to this problem and have found nothing. So I thought I would post for future folks that might be interested for another data point.
New to me 2019 Cherokee Latitude with tow group. Rear end definitely binding during sharp slow turns under power only. Driving in a circle in a parking lot type of thing.
It wasn't just a noise...it was actually as if the rear was trying to lock the diff, so can be felt as drag along with the noise. Dealer suggested a SW update to fix the issue. I was skeptical but after 15min at the dealer, noise and binding is gone.

Edit...the following is wrong, proven by Tyler-98-W68, left it here for reference.
So if the the car is supposed to be in FWD only, unless power to the rear is called for due to wheel slippage, I would expect the problem is not in the rear but with the front wheel speed sensors. The symptom manifests at the rear because it's calling for rear power when it's not needed and on a surface where no slipping of the rear, semi-locked diff attached wheels will allow.
The tires were new on this when I got it. I'm wondering if it's possible there is some learning of tire diameter, and as the tire decreases diameter over time, the wheel speed algo compensates. But with new tires and hence, possibly larger or different diameter than the ones as they were removed, does that confuse the speed sensors into thinking there is slippage as the front, so give power to the rear. Anyway, that's my theory

I suspect this is a common situation....most people that drive these around probably don't notice the symptoms enough to care.
But at this point, problem is solved for me.

 

[Tyler-98-W68]

Sharp binding while turning is usually the RDM (rear diff going bad)

Pulling the F10 fuse can help diagnose the problem. If the issue goes away with the F10 fuse pulled (which disables the PTU) the RDM doesn't get power. There is no learning of the diameter of tires.

So if the the car is supposed to be in FWD only, unless power to the rear is called for due to wheel slippage, I would expect the problem is not in the rear but with the front wheel speed sensors. The symptom manifests at the rear because it's calling for rear power when it's not needed and on a surface where no slipping of the rear, semi-locked diff attached wheels will allow.
The tires were new on this when I got it. I'm wondering if it's possible there is some learning of tire diameter, and as the tire decreases diameter over time, the wheel speed algo compensates. But with new tires and hence, possibly larger or different diameter than the ones as they were removed, does that confuse the speed sensors into thinking there is slippage as the front, so give power to the rear. Anyway, that's my theory

There is no slippage required to send power to the rear there is always power going to the rear wheels at low speed and when the system in functioning properly there is no binding to be felt.

 

[AP2019]

Sharp binding while turning is usually the RDM (rear diff going bad)

Pulling the F10 fuse can help diagnose the problem. If the issue goes away with the F10 fuse pulled (which disables the PTU) the RDM doesn't get power. There is no learning of the diameter of tires.



There is no slippage required to send power to the rear there is always power going to the rear wheels at low speed and when the system in functioning properly there is no binding to be felt.

Thanks Tyler. That's interesting. What are your thoughts as to what they changed with the SW update? I'm 100% certain it was showing these symptoms before the update and not doing it afterwards, 15 min later. Do you think they could have reduced front to rear power transfer to the point where it's all front?
I should mention the binding was only under power in a tight radius, slow speed turn. While off throttle and coasting, displayed no noise or bind. I think the update has a ref number that may be on the work order. Does anyone have access to descriptions of SW updates?
Also, I'm curious, are the rear diff clutch packs solenoid controlled? If so, maybe that's what the SW changed...?
Andy

 

[Tyler-98-W68]

That's interesting. What are your thoughts as to what they changed with the SW update? I'm 100% certain it was showing these symptoms before the update and not doing it afterwards, 15 min later. Do you think they could have reduced front to rear power transfer to the point where it's all front?

I hope not because that behavior has been observed after PTU replacement on prior years. I would not expect this to be a fix for 2019+ non trailhawks as they use the 2nd generation AAM Ecotrac AWD system.

The proper operation of the AWD system is to be engaged at low speeds and under a bunch of circumstances. I've outlined them here

AAM Ecotrac AWD Operation Testing & Data with Alfa...

I’ve had some time to use an app called AlfaOBD along with a OBDLink MX+ Bluetooth adapter to analyse and data log both my 2014 and 2016 Cherokee and better understand how the AWD system works, and as I had posted in THIS thread I have some better videos to show how the AWD system works and the...

www.jeepcherokeeclub.com

AAM Ecotrac AWD Operation Testing & Data with Alfa...

AAM Ecotrac AWD Operation Testing & Data with Alfa OBD,Selec Terrain Modes Compared Had some more time to play with my Fiat and test out the rear torque transfer with Alfa OBD and how it related to each selec terrain setting. The first 4 videos are with the vehicle in each selec terrain...

www.jeepcherokeeclub.com

I happen to have a 2014 which had a PTU replaced and its awd system was seriously changed (for the worse) after replacement. I've detailed that in this thread here

AWD System Operation Differences after PTU Replacement

Some people have had their PTU replaced and have noticed a difference in AWD operation post PTU replacement. My 2014 Cherokee had a PTU and RDM replacement less than 1 week after it was purchased new. Ever since the replacement there has always been a noticeable amount of wheel spin prior to...

www.jeepcherokeeclub.com

So in the above case my 2014 never had the binding problem the PTU and RDM just destroyed themselves and the issue with the AWD system came up. After all these years and testing i've come to the conclusion that the clutches in the RDM are worn out and not engaging enough except in the sand/mud mode. So yes it's entirely possible they changed the AWD system programming.

Easy way to test it out. Put it in sand/mud mode and do a slow turn you SHOULD get binding on high traction surfaces at low speed. But not in any of the other modes.

Another way to think of power flow in the AWD system is

Engine sends power to the PTU, PTU spins the drive shaft to the RDM, then the RDM applies clutches which ultimately provide power to the rear wheels. The PTU can spin the driveshaft to the RDM without having the rear wheels receive any power

 

[AP2019]

Love it. You have data to back it up. That is much more information than most of the Jeep employees know about how the system works. I suppose it's all just supposed to work, and we're not supposed to know it's there, but I have a problem where I like to have some understanding of what is going on! Thanks for that info and saving me the trouble of looking further.

"Easy way to test it out. Put it in sand/mud mode and do a slow turn you SHOULD get binding on high traction surfaces at low speed. But not in any of the other modes."

Yes...I was thinking same thing and to try just that this evening after work.

I edited my initial post to keep the topic clear to future readers.

Thanks!

 

[Trailfirst]

Damage to the drivetrain from uneven tyre wear is utter rubbish. That assertion relates to uneven wear causing slight differences in rolling diameters and so different rotational speeds. A moment of contemplation about the effects of even slight pressure differences between tyres - as well as load distribution in the vehicle - not to mention what goes on during normal driving even thru slight curves and turns - ie. anything other than dead straight road - will show any of that nonsense about uneven tyre wear to be the complete rubbish it is.

 

[cubedtothex]

I have a new to me 2019 Limited 4x4 and this is the exact problem I’ve been having. It was purchased with only 12,000 in June and I started experiencing this. It’s my first 4WD vehicle as I had a FWD version of the same trim with the weak 2.4. It was totaled in an accident and since it was life-saving we decided to get another, but wanted more power with the 3.2L V6. The only ones we could find were 4WD so we took a chance. It drives great (much better than tge 2.4L) except the grinding in turns at low speeds under power. It’s been sitting at the shop for two days due to lack of technicians after making an appointment two weeks in advance (created a frustrating few days, but the GM stepped in and my rental is covered). I got a call today that the rear diff needs to be replaced. They have to order the part or get it from another dealer. Once I knew the issue, it was easy to research. Thanks for continuing this thread as it’s been very helpful in helping me understand the issue!