Jeep Grand Cherokees those tend to have several common mechanical problems. The problem today is that we cover with loud differentials (rear ends). While it is acceptable for Jeep differentials make some noise, it is not good to ignore the noises are more moderate than gold if the noise is getting louder. Typically rear whine noises are Jeeps rated on a scale of 1 to 10, anything below 5 is acceptable and would not warrant repair. If a roar is heard, this is another matter, the roars should be examined immediately. I have rebuilt hundreds of rear ends and of those about 80% have been on Jeeps. Also, the Jeeps I have worked on were not driven off-road or abused in any way that I could see. They were driven mostly like a normal family car would be, so this leads me to the conclusion that this is just a common problem due to the design.
Roaring noises They are one of the most common sounds that makes a Jeep Grand Cherokee from the rear. As I mentioned earlier, if roars are heard, this should be addressed as soon as possible. Typically around 45 mph est. When the sounds start coming from the rear. If Heard is roaring at all speeds or car parking, the problem has progressed. The roars come from worn bearings and chopped. Carriers bearings (qui are side bearing) are the most common bearings fail. Below are the bearings of the pinion, the pinion seal, especially if replaced at some point and the bearing preload was excessive. This means that the pinion nut is tightened too. Tighten the pinion nut can be caused by excessive load on the pinion bearings and bearings can wear out in a short period of time. If replacement of the bearing is delayed too long, the metal can travel through the differential oil and damage other moving parts of the differential. This can cause accelerated wear of the ring and pinion gears. Therefore, if detected early enough, the bearings can be replaced without replacing the ring and pinion gears.
Crown and pinion That gears are excessively worn or hum make a whimper, sometimes there are acceleration and deceleration times. And they are more expensive to replace than just the bearings. Pinion gears and ring can emit a squeak without a roar from the bearing occurs. Purpose To replace the pinion and ring gear is recommended also replace other bearings, including two pinion bearings and bearings. Shaft bearings should be inspected, but are farther away from the gears and bearings of the differential, so chances are they are well, especially in lower mileage vehicles.
Used rear ends should be avoided for jeeps in my opinion. The reason is because this is a common problem so the chances of getting a good one from a salvage yard are slim.
Noise Park in the parking could only be just a noise limited slip clutch (posi-drive). In this case, try putting an additive designed for clutches. Ask for limited slip friction modifying additive posi gold. Some of driving the vehicle allow the change to soak in the grip and hopefully prevent prevention em grab.
