2011 Jeep Grand Cherokee rear end sagging

Shocks don't set ride height, springs do. That's the key thing. A shock is just a damper, it controls bounce. If your rear sits lower than it should and bottoms out, that's a spring problem, not a shock problem, in almost every case like this.

Here's how to sort it on your 2011. First, check if you have Quadra-Lift air suspension. If you do, the rear sits on air springs, and a slow leak in one is the most common cause of sag there. Listen for the compressor running constantly and look for cracks in the rear air bladders with soapy water.

If it's the standard coil setup, get under it and look at the rear coil springs themselves. At 149k miles they sag or crack, usually at the bottom coil where it sits in the spring perch. Rust belt Jeeps break them there. Also check the rubber isolators top and bottom, since crushed isolators can drop the rear close to half an inch.

Do the bounce test too, just to check the shocks. Push down hard on a rear corner and let go. More than two bounces means the shocks are shot as well, and at your mileage that's plausible. But worn shocks alone will not raise the truck back up, so don't spend shock money expecting the ride height to come back.

Start with the springs.

https://ezcarfix.com/blog/suspension-diagnosis-guide