Recently purchased a 97 Cherokee XJ Sport. The previous owner had installed a Rough County 1.5 lift himself and was running 31/10.5 tires. The Jeep drove like a boat wandering all over the place with some noise. I took it to a mechanic that owned two XJs himself he said the lift wasn’t installed correctly and it need a 3” lift to run that size tire anyway . Put the new 3” Rough County lift on the Jeep and steering and ride was was fixed. Still had the noise so I replaced both front wheel bearings, new u joints in the rear driveshaft and checked the other u joints. About 70 percent of the noise if gone. The only problem left is a rumbling when you let off the gas at 35 mph or more with a slight vibration? I was thinking maybe the drive shaft angle and installing a slip yoke eliminator kit but I’m not sure? Any ideas on what else this might be or that I should check before throwing more money at this rumbling noise?

I would start with a slip yoke eliminator but also check the pinon bearing .

Have you measured the angle of the rear axle pinion; perhaps just shimming it will fit the issue without needing a SYE...

Try removing the front driveshaft and see if that makes any difference. Mine was a bit too short with fixed length aftermarket LCAs and the NP242...