Qd2 just does the jerking thing on tight turns*. As to your light and the HARD jerking it sounds like an abs issue.

*my guess as to why the WK2 doesn't have a front elsd. Jeep got tired of dealing with people hating how the thing turned like Michael J. Fox.

 

check the wheel sensors.

 

Had the exact same issue when my steering wheel clock spring went out. Abs light would come on and when turning at slow speeds it felt like differential wind up that would "let go" and violently jerk the whole Jeep.

Replaced clock spring and it went away never to come back.

 

Folx,

much obliged, will use the tips to see whats going on and make sure to post root cause here.

 

Autozone scanner didnt show any codes - but it cant read Chrysler ABS.

Checked front wheel speed sensors - both read open one way, about 1.5M the other way. I guess these are Hall-effect sensors.

Had a helper look at the wheels as I slowly drove around in tight circle. It is definitely a rear wheel that somehow binds - either the brakes get activated on it, or something worse happens .What else could it be though, outside of rear diff ? Did check oil in rear diff - it is fine. I did replace all the fluids about 25K miles ago - remember using special LSD additives. Had dealership replace tranny fluid too.

Removed the ABS pump fuse and drove around - same symptoms. Now, if it was ABS somehow braking rear wheels, it shouldn't do that with ABS pump not getting any power.

Wish I could try the wheel clock spring theory.

 

See if you can deactivate rear elsd for testing purposes.

 

How would I do that - unplug the actuator connector atop of the rear diff ?

 

Here is the root cause.

It was rear right ABS sensor.

I most highly recommend buying "BlueDriver" ODB reader on Amazon. $100, it communicates via Bluetooth to the "Torque" application on your phone. Worth its weight in gold as it does read vendor-specific codes , including Jeep's ABS

The replacement sensor is $20 on Amazon.

Here's how to properly test your sensors: your meter must be in "diode" position. The sensor should read about 1600 Oh one way and open circuit the other. Mine was 1600 Ohm one way and about 4K the other.

The sensor has diode in series with a coil - that's how you get the readings I described.

To replace rear sensor, remove rear wheel. No need to remove the rotor or brake calipers. Single bolt.

Mine was kind of stuck in there, took some WD40 and prying/turning to get it to come out. I cleaned the hole with some sandpaper and installed the new sensor. Pretty ez job.

While it did feel like differential binding and $10000 repair, $20 sensor is all you need to fix it.

While on it, do consider replacing both diffs and TC fluids, 30K is the interval. $5 fluid transfer pump at Harbor Freight is just the ticket to both suck the old fluid out (no drain plug on rear diff) and pump new one in.

Must use Chrysler LSD additive.

Jeep Grand Cherokee rear wheel ABS speed sensor replacement, violent jerking jerks lurches lurching when turning. Differential binding.

 

Good to know about that!
BTW, as long as you use the Chrysler friction modifier the QD2 system does not bind; if it does something is wrong