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Advice Needed - Stick with my old and possibly failing rear diff, or put in a used one from a junkyard?

1159 Views 20 Replies 12 Participants Last post by  lschirm4
Hello!
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 :)
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I would suggest replacing the bearings in what you have. A shop that knows what they are doing shouldn’t charge more than $1000, parts and labor.
You can damage the housing if you keep driving it.
A used one needing bearings now or on the near future is about 50/50.
 

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Discussion Starter · #3 ·
I would suggest replacing the bearings in what you have. A shop that knows what they are doing shouldn’t charge more than $1000, parts and labor.
You can damage the housing if you keep driving it.
A used one needing bearings now or on the near future is about 50/50.
The mechanic says the bearings, gears, and carrier are all worn to the point that he doesn't think anything less than a full rebuild or replacement would be worthwhile.
 

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As long as the diff housing is in good shape and you have not spun the bearings you can just rebuild this one. As a side point you said you had the D 44HD and not the usual D44a. If it is the cast iron HD I would rebuild it, but if it's the aluminum 44a you will need to look at the bearing mount area to be sure you didn't spin the bearings in the housing.
Having said that you can buy a new carrier, master rebuild kit and I would suggest new axle bearings and seals since they will have to come out to remove the carrier. Total parts should be less than $800. I don't know what a shop in your area would charge but you can shop around for a drivetrain shop that would give you an labor estimate.
 

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Discussion Starter · #5 ·
As long as the diff housing is in good shape and you have not spun the bearings you can just rebuild this one. As a side point you said you had the D 44HD and not the usual D44a. If it is the cast iron HD I would rebuild it, but if it's the aluminum 44a you will need to look at the bearing mount area to be sure you didn't spin the bearings in the housing.
Having said that you can buy a new carrier, master rebuild kit and I would suggest new axle bearings and seals since they will have to come out to remove the carrier. Total parts should be less than $800. I don't know what a shop in your area would charge but you can shop around for a drivetrain shop that would give you an labor estimate.
Do you think a rebuild is realistic even with worn gears? I'm now weighing whether I need to ditch my mechanic and get a second opinion. Seems that finding all the parts for this thing for a complete rebuild isn't very easy - I'm seeing some kits with all the bearings, but the gears are another layer of difficulty.
 

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It would be a no brainer if you could do the work yourself. I agree with hanlondave95 that it's unlikely the gears are beyond use. If Kolak can ship to Canada I would get all the parts from him as he knows Jeeps very well. Ask him about shipping first before you have him do all the lookup work so you don't waste his time.

The metal shavings could be spider gears and other wear components, however the pinion and ring gears are made differently and may be OK. Did he use a magnet to see if the shavings were steel or aluminum.
 

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Discussion Starter · #9 ·
It would be a no brainer if you could do the work yourself. I agree with hanlondave95 that it's unlikely the gears are beyond use. If Kolak can ship to Canada I would get all the parts from him as he knows Jeeps very well. Ask him about shipping first before you have him do all the lookup work so you don't waste his time.

The metal shavings could be spider gears and other wear components, however the pinion and ring gears are made differently and may be OK. Did he use a magnet to see if the shavings were steel or aluminum.
What he told me was that the shavings were coming out on a magnet, so presumably they are steel. I'll take a look into Kolak
 

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Unfortunately I'll need to take the mechanic's word on this one - wouldn't the presence of metal shavings in the oil indicate gear damage? In any case he's not interested in a rebuild without replacing the gears, so I'd need to find someone else.
The metal shavings are going to be mostly from the failed bearings. In 35 years of working on Jeep and 4WD vehicles, I’ve replaced 100s of bearings and I can count on one hand the gear sets the were damaged.
Yeah I’d be finding another place with more rear axle experience.
 

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I Agree with MaineJeep04
 

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MaineJeep04 is the one asking the questions.
Maybe you agree with hanlondave?

I'm thinking with hanlondave and you have little in the way of risk to have one more shop take a look. If they are truly inspecting it, they are pulling the cover, right? Labor and fluid costs... for what may be a better path.

I'm thinking if you just need another year or so out of it, the boneyard option is too good not to consider. Also, get a pic of those shavings or bearing materials that are being observed, folks here know the type of stuff that's a real problem and what's not. If the prior shop did a full inspection, they pulled the cover and put in fresh fluid too so it will be interesting to see what's on the magnet now.
 

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Discussion Starter · #13 ·
Thanks everyone for the responses. I'm having another reputable shop take a look tomorrow before I go down the rabbit hole of obtaining a used diff and going through the hassle of having it switched out. Hopefully the gears are still usable and I can get away with just replacing the bearings.
 

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I’d just switch out the diff. The used ones shouldn’t be too bad on wear and tear if you grab one from a soccer mom mall crawler Jeep. Everything will bolt up. Get an open diff then add a limited slip or locker of your choice.
 

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Given the relative cost of labor to R&R the rear diff, no shop is going to want to reinstall used gears.

I wouldn’t even do it myself, my time is worth more than that. If I open one up it’s all going back new.

I do understand the OP’s dilemma on cost vs vehicle value. I’d probably go the junkyard axle route if you can get one that’s not a rusted POS.
 

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I took mine to a shop to get the rear diff bearings replaced and they had fits trying to find the right parts for my 44HD. I gave them all the part numbers but they ended up picking an axle up at the Pick and Pull, sandblasting, and painting it before installing. The gear oil they used was causing the diff to grind during sharp turns so I drained it and filled with gear oil Mopar friction modifier. If I had a garage I would have done the whole thing myself but all I have is dirt outside.
 

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I fully agree that bearings are more often than not the only failure in a diff. The gearsets and carrier can still give good service. Unfortunately, there are not many shops that really have guys that are well versed in diff repair. Even just doing bearing replacements competently. A transmission shop may be your best ticket to find a smaller ma a pop shop that is competent rather than a general repair shop.
 

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It sounds as if the OP doesn’t plan to keep the WJ. In which case go the cheapest route Which may be rear axle junk yard swap out. Those usually come with a 30-60-90 day warrantee. If it lasts 2 weeks without problems you’ll be fine for a long long time - my rear has 242k miles and has no issues. Anything in a junk yard likely has less but a good yard will tell you the mileage on it.

If you could change your mind on keeping it then this is a great opportunity for upgrades.
 

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You can get diffs out of junkyards in CO for a fair price (mine was $600 shipped) and swap it out with a buddy and a case of beer. Just need to make sure you get the correct ratio gear set. If you do not have the gears setup correctly, they fail in short order. Pinion depth and side clearance are important to the life of the unit. You need a special pinion depth measuring tool and a dial indicator for all of it. $1000 bucks for oh four hours works seems excessive. Me and a mechanic buddy did one in an hour and a half, but we read each other's minds and work just flows.

I have the tools to do a gear set since I fix a lot of high milage worn vehicles that a ready for some serious repair. I still avoid it since there are so many low milage units in junkyards no one wants.
 
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