Rear End Noises. Loud, steady groaning, plus clunking sound on 1994 Jeep Grand Cherokee

94 Jeep Grand Cherokee Limited 5.2 V8 (ZJ). Completely stock with 250k miles. All of the drivetrain and suspension parts are original. Plan to keep it stock.

A loud, steady groaning sound from the rear end at speeds from 20 mph and up. Worse at about 50 mph, a little better at 70 mph plus, but even worse when about 30 mph and breaking to a stop. This groaning sound has been around at least 100k miles but has become worse.

There is also a clunking sound when making right hand turns, from a stop, under throttle. This problem's been around less than 2k miles. I’m guessing the noises are related to rear wheel bearings and / or the rear differential gears / bearings (probably bearings).

Wheel Bearings - Last repacked at about 130k miles. A mechanic noted "rear bearing noise" as a problem on an old invoice when the brakes were last done at 175k (brakes working well now with 25% remaining per dealer). I'm guessing he was referring to differential bearings and not wheel bearings.

Rear End - the rear differential leaks pretty bad up at the driveshaft (or is it the pinion?) but has been serviced often enough to not go dry. Original Dana 35 w/ limited slip. And the moaning noise has been present for many years, before the rear end ever leaked.

Question - I'll have to take it to a mechanic. I understand that the rear end and bearings cannot be fully evaluated until taken apart. And I am no mechanic.

Assuming the mechanic finds that the rear diff bearings need to be replaced but most of other parts are good, and maybe the wheel bearings need to be repacked / replaced, would it be better to:

a) Have the rear end rebuilt and the axle bearings replaced (repacked?), or

b) Just get a whole new stock rear end with axles installed (Dana 35, I think 3.55 gears).

c) Upgrade to a new Dana 44 with similar gearing, without upgrading or replacing other parts.

Any idea on the range of costs for a), b) and c)?

And the same question if most of the rear end gears and parts have to be replaced.

Asked by for the 1994 Jeep Grand Cherokee
With the mileage you have accumulated on this vehicle, you are fortunate. Pinion bearing failure is the most common on the Jeep differentials as it turns 3 to 4 times faster than axle or carrier bearings, however if you are going spend the money to fix it, do it right by replacing ALL of the bearings and U-Joints and if equipped with limited-slip (Trac-lok), the carrier assy.. The clunking noise on turns could be the limited slip clutches. Proper limited slip fluid additive must be used every time the fluid is replaced
2 answers
First, (nearly) every Jeep will start to leak from the pinion seal (front or rear). Diff covers also.

There is a chance the groaning could be your carrier bearings or axle/wheel bearings, or both. I am assuming the clunking you mention is from the rear of your Jeep, that may be your limited slip starting to go south too. It also may mean you need to change the fluid again and use the correct limited-slip additive.

With Jeeps you have an amazing amount of options because of people modifying them for off-road or rock crawling. What you decide to do I think depends on your goals. If you're doing daily driving, stock tire sizes, the Dana 35 should be fine. If you've gone larger on your tires, and go off-road the Dana 44 is an option. The Dana 44 that came on some of the V8 Grand Cherokee's does not have a great reputation for strength because of the cast aluminum housing.
I am more familiar with Toyota crawlers but sites like JeepsUnlimited and Pirate4x4 will have info on axle swaps so you can know what to look for used (use the search functions and read the FAQ before posting questions). That leads to the next option. With people swapping to Dana 44's and 60's, you will probably be able to find a stock 35 complete drum-to-drum. A lot of wrecking yards specialize in Jeep parts too. ( for example)

I'm afraid I can't say what a rear-end rebuild will cost without knowing what exactly what you need. I would look into the price of a used, good axle, and then decide if it's worth rebuilding your original axle.
If you feel like reading some tech, I have used this for my friend's Wrangler and my Toyota