[JCT5509]

Hi All,
I'm new to the forum and am posting because my wife's Cherokee has a problem that has me very puzzled and am hoping someone here can provide some guidance.

We have had the vehicle since new it currently has a little over 70 k miles and until last week has been trouble-free and performed flawlessly. We had the Cherokee's front end aligned after installing new tires on the front, the back tires were not replaced and the rear was not aligned.

The transaxle in this ride has always had silky smooth upshifts. Downshifts when coming to a stop can be felt but nothing extraordinary. There are no outstanding recalls on the vehicle, and it has never been part of any of the past trans recalls. We seem to have gotten a good one!

Now the car has what I can only describe as a surge or a slight drivetrain bump when driven between 30-40 mph, you can feel it in the seat of your pants, under the trans tunnel, though it does not seem to occur while shifting.

There is no noise associated with the surge/bump. When this occurs there is no change in the rpm, the transaxle doesn't bang or make any noise at all nor does it shift hard. The vehicle's performance is not hindered in any appreciable way.

No fault lights light on the display. We viewed the transmission temp while driving and the issue started when the trans temp was at 95F so I don't believe it's heat-related. Terrain does not make any difference on when it happens, It will occur when diving on level ground or going uphill, under normal acceleration, or hard.

Visual inspection has revealed nothing out of the ordinary, no loose parts no leaks.

Any ideas?
Any Assistance is greatly appreciated
thx
J

 

[sanghill]

#1, all 4 tires need to be nearly the same diameter. Since you only installed new tires on the front that could be the problem. You probably have AD2?
If the drivetrain has been damaged by different tire diameters it won't fix itself even with new tires on the back.
Check the drive shaft for loose joints and slinging grease.
There may be some TSBs that may need to be done.
Refer to this Post: List of up to date TSB Post #22 (expand the list)
Your Jeep dealer can determine if any of these TSBs are applicable to your Jeep.

#2, a 4 wheel alignment with a complete suspension inspection is required to do the alignment correctly.
Worn suspension parts can prevent a proper alignment.

 

[JCT5509]

#1, all 4 tires need to be nearly the diameter. Since you only installed new tires on the front that could be the problem. You probably have AD2?
If the drivetrain has been damaged by different tire diameters it won't fix itself even with new tires on the back.
Check the drive shaft for loose joints and slinging grease.
There may be some TSBs that may need to be done.
Refer to this Post: List of up to date TSB Post #22 (expand the list)

Thanks for the quick replay
The tires are the same size all factory spec, I don't think its ad2 as we have no low range of the selector knob. One thing I forgot to mention in my original post is that it does this even when the trans is shifted manually, not sure if that makw a difference or not

 

[sanghill]

You should be ok.
The gear shift selector does not actually select a specific gear, it only selects the highest gear the computers can choose from.
The computers select the actual gear to use.
If you have AD1 then you probably do not have a drive shaft.
There are some TSBs for shift enhancements but you will need to consult your Jeep dealer to figure out which ones apply.
I think there was a TSB to replace the front half shafts, determine if this is applicable.

 

[JCT5509]

So do you think having the rear aligned would be the frugal thing to do? I will check the TSBs

 

[sanghill]

Since you don't have 4WD you probably don't need to get a 4 wheel alignment done.
When you get your tires rotated have the guys check for uneven tire wear that would indicate an alignment problem.
I have never had a problem with wheel alignment as it came from the factory.
The Cherokees seem to be real good at keeping good wheel alignment.
You are low mileage so you should be ok.

 

[Mark_]

Since you don't have 4WD you probably don't need to get a 4 wheel alignment done.
When you get your tires rotated have the guys check for uneven tire wear that would indicate an alignment problem.
I have never had a problem with wheel alignment as it came from the factory.
The Cherokees seem to be real good at keeping good wheel alignment.
You are low mileage so you should be ok.

They have a Selec Terrain knob so it is AD1. AD1 is AWD, just no Low range or Neutral in transfer case (PTU). AD1 has a driveshaft.

 

[Skidmark]

I would consider replacing the rear tires as well. If they have 70k on them, they will be different diameters, like sanghill says. This can trigger some odd bumps/clunks in the ZF948TE because, unlike some other transmissions, they use dog clutches for a couple of the gears instead of all hydraulic clutches.

 

[topfuel83]

Wow, really poor knowledge of the KL platform here.

First of, there are 4 types of drivetrains.
1. Front Wheel Drive
2. Active Drive 1
3. Active Drive 2
4. Active Drive Lock (Trailhawk)

If there is a terrain select knob it has active Drive, is considered all wheel drive, and has a rear driveshaft.

Any vehicle alignment on the KL should always be a 4 wheel alignment due to suspension geometry.

Given that it is all wheel drive (when the computer engages the rear driveshaft), all 4 tires should be fairly close together in size and replaced together. The owners manual spells this out.

Your problem is the mismatched tire sizes with 2 being new and 2 being old, even though they are all OE. Have 2 new tires put on the back as well, get a 4 wheel wheel alignment, and hopefully no damage accrued to the PTU and the problem will resolve itself.

 

[Mark_]

Wow, really poor knowledge of the KL platform here.

You sound familiar.

 

[1coopgt61]

You sound familiar.

It couldn't be someone that bought a Hybrid JK last year could it .

 

[Mark_]

It couldn't be someone that bought a Hybrid JK last year could it .

Don't know what you're talking about... ... ...🚫

 

[JCT5509]

Thanks for all the input...two new tires and a wheel alignment it is

 

[JCT5509]

Another question should I pull the 4wd fuse, number 10, until I can get the tires and alignment? It is my understanding this will prevent the PTU from engaging.

 

[sanghill]

This is my opinion:
I like to get my 4 wheel alignment done by a Jeep dealer.
They have the proper laser equipment and the correct software specifically for your Jeep.
They will set the machine up for your specific drivetrain, correctly.
If an adjustment is needed they will know how to do it. Lets just say the procedure is 'strange'.
Some alignment settings are not adjustable.
Wait until you get the new tires before the alignment is checked and if necessary adjusted.

The tire store will probably want to do an alignment.
That is fine if they will do it for free, get the printout, don't let them adjust anything. Then you can compare it with what Jeep measures.
Don't even let them check the air filter, they may strip the threads in the air box or break the EGR hose fitting.
Make sure they don't mangle the beer can lug bolts, visual inspection, if a 19 mm socket goes on correctly they are good to go.
Do not let them change the TPMSs in the wheels. Wait until the battery dies, then change them. They are also expensive. They are not critical to Jeep operability.
I buy my tires at a Firestone store because I use Firestone Destination AT tires, generally they do good work but sometimes stuff happens.

The above is based on 9 years of experience and I have bought lots of tires.
When the tires get to 1/2 tread depth they get replaced, I need all the traction I can get off road.

 

[topfuel83]

Another question should I pull the 4wd fuse, number 10, until I can get the tires and alignment? It is my understanding this will prevent the PTU from engaging.

Yes, pulling the F-10 fuse will disable the PTU, and give you the ability to safely drive it until you get new tires.

 

[JCT5509]

I appreciate your input, but I will probably take the vehicle to the tire store that did the fronts, the dealer we bought the Cherokee from has changed hands, and isn't worth the powder to blow them to h-ll now. Have had multiple issues with them and won't be giving them any more business.

 

[JCT5509]

Yes, pulling the F-10 fuse will disable the PTU, and give you the ability to safely drive it until you get new tires.

THX much, will do that today

 

[JCT5509]

Had the rear tires replaced and the rear aligned...fixed the issue all is well. Thx much for your assistance

 

[Lindy]

You sound familiar.

I thought the same thing. lol