First post here, apologies if I missed anything obvious. I'm generally familiar with automotive concepts but I'm not an expert mechanic by any means.
I've got a 2004 WJ with 193,000 miles on it, located in interior British Columbia. The rear differential has been making an oscillating whooshing/light grinding sound, especially noticeable when coasting at speeds below 40 mph. Sounds a bit similar to a jet plane flying overhead. It's noticeable but doesn't sound catastrophic at this point. It's been making this noise for maybe a year or so now, and seems to be slowly getting louder over time. It's a Dana 44 HD.
I've taken it to a mechanic who took off the cover and said there was a moderate amount of metal shavings in there, and said that several of the bearings are worn/damaged, necessitating a full rebuild. Diff oil was replaced last year with mechanic also noting some metal shavings, but not as many.
A new diff + install would cost over $3,000 (Canadian, but still too much) and at this point in the car's life I can't justify that. I can get a used one from a junkyard for $350 and have it installed for less than $1,000 (although the mechanic won't guarantee anything with the used diff). My question to the Jeep forum hive mind is this: Is it worth going through the hassle of getting the used differential at this point (with the risk that it won't be much better than mine), or should I drive it until it's obviously falling to pieces before I go down that rabbit hole? I'd obviously prefer not to get stranded on the side of the road, but it's unclear to me if this thing will explode tomorrow or if I'll get another 50,000 miles out of it. Any chance it'll do something crazy and cause a major safety hazard? Or is it more likely to be a slow progression to louder and louder grinding noises until it's toast?
For what it's worth, I'm not doing any major off-roading in this thing, just using it as a daily driver with the roughest conditions being the occasional potholed forest road. I'm on the waitlist for a new PHEV RAV4, but unfortunately I'm stuck with this thing for another year or two before that's ready and I'd like to keep it running without breaking the bank.
Any advice appreciated! Thanks everyone