Rear noise in JGC 2000...

[mvbighead]

4.7 V8, Quadtrack Jeep Grand Cherokee with 150K+ miles.

If I am driving at any speed above 25-35, there is a whirring noise coming from the rear end. My last bit of googling seems to suggest rear differential bearings (or gears) as the noise changes as the throttle engages and disengages (gas pedal pressed then released).

Does that sound right to you guys?

I was hoping it might be rear wheel bearings, as that seems to be an easier repair job; but the change in tone when the throttle is released seems to suggest otherwise, unless I am missing something.

I have been doing some DIY lately, but from the sounds of it, this may be above my level of ability, maybe not though. I've thought of removing the plate on the diff and changing the oil there, as I have no idea when that was last done, but elsewise don't know where to start with the differential.

 

[ViviTheMage]

could be bearings, could be the differential ... does it only happen when pushing the accelerator in gear, or does it happen if the car is just rolling?

 

[mvbighead]

could be bearings, could be the differential ... does it only happen when pushing the accelerator in gear, or does it happen if the car is just rolling?

It is louder when the accelerator is pressed, but it still seems to be present when rolling, just a much lighter noise.

 

[ViviTheMage]

being RWD, possible it's the wheel bearing ... when my dif was acting up, you would really only hear it when accelerating, or pushing the gas at all.

 

[mvbighead]

being RWD, possible it's the wheel bearing ... when my dif was acting up, you would really only hear it when accelerating, or pushing the gas at all.

I suppose the other noise could just be tire noise. They are all-season truck tires with fairly rough looking tread (not mudding tires by any means, but not a standard passenger tire either). Honestly at this point, I hear the major noise fade and am really keying in on it to hear additional noise.

I should probably just go for a ride in my SIL's Jeep and see what the difference is.

 

[ViviTheMage]

We had a 05 GC 4.7L ... never had rear noise, we had pretty decent sized mudder tires too. You would probably know if it was tire noise/road noise vs differential/bearing.

Have a buddy try to listen while driving it yourself...or have a mechanic friend sit with you, it would be pretty evident for them what to start looking at.

 

[mvbighead]

We had a 05 GC 4.7L ... never had rear noise, we had pretty decent sized mudder tires too. You would probably know if it was tire noise/road noise vs differential/bearing.

Have a buddy try to listen while driving it yourself...or have a mechanic friend sit with you, it would be pretty evident for them what to start looking at.

Unfortunately, all of my DIY was stuff is solo, and I have no good mechanic friend to go with me. Hence a post about every car problem I ever get being posted here for help in further diagnosing.

Or, I may just decide to take it to my mechanic and see what they can do for me. Might just be wisest to go that route. But, from the sounds of it, this may set me pack a fair penny (roughly $1k). I'd much prefer to exhaust my own options before I drop major coin into this thing. It has had its share of minor issues, but this would be the first major thing to crop up.

 

[mvbighead]

Would it hurt to check/replace the differential fluid?

Or should I just schedule an appt to get this looked at?

 

[ViviTheMage]

Would it hurt to check/replace the differential fluid?

Or should I just schedule an appt to get this looked at?

Does the fluid look discolored? Has it ever been done before, that you know of?

What year? IF you want to check a few things yourself, and I usually have my mechanic do it, but I think there's a test you can do with the wheel off to see if the ball bearings are shot...if they are not shot, then you know something is up with the dif.

Maybe someone here knows how to do that, or google it and see what comes up. I have to imagine someone on AT knows how though.

 

[mvbighead]

Does the fluid look discolored? Has it ever been done before, that you know of?

What year? IF you want to check a few things yourself, and I usually have my mechanic do it, but I think there's a test you can do with the wheel off to see if the ball bearings are shot...if they are not shot, then you know something is up with the dif.

Maybe someone here knows how to do that, or google it and see what comes up. I have to imagine someone on AT knows how though.

Both unknown at this point, but I am guessing no.

2000 is the year, and I would be curious as to the test as well. In one vid, I saw a guy jack it up and rotate the wheel by hand. Seemed to be a much older vehicle, but I suppose that might tell me something.

 

[ViviTheMage]

Both unknown at this point, but I am guessing no.

2000 is the year, and I would be curious as to the test as well. In one vid, I saw a guy jack it up and rotate the wheel by hand. Seemed to be a much older vehicle, but I suppose that might tell me something.

yeah, that sounds like what my buddy does when he checks ... I think you don't want it to move vertically if you have it in the air, if you do, it's getting bad...I THINK that is how it's done.

 

[mvbighead]

Well, I guess to start things off in figuring this out, I'll plan on grabbing the gear oil to clean that up and inspect the gears. If they're fudged, I'll just put new fluid in there and get her to a shop ASAP.

Will also inspect the wheels for any play and see if I can figure anything out there.

In any case, swapping the fluid should be less than a $50 job, and hopefully not much longer than an hour. Will give me a chance to make sure things are in bad shape and then be sure that further service is necessary. I hope to get it recorded so as to be able to display the results to anyone who can maybe determine from a poor cell phone video as to whether they can see something I can't. At this point, I am leary driving it any more than I have to, as I don't want to break it and force a major repair on myself if I can avoid it. My guess with the sound though, is that I am may already be to that point. We'll see.

 

[ViviTheMage]

Yeah, it's a start...if you can put it up too, try the tire thing, see how much give it has.

 

[mvbighead]

Well, I didn't dig into this last night, as I was just a bit too zapped to deal with, and the wife and I figured we'd carpool anyway so the Jeep gets to sit.

I did buy the supplies, but am now realizing that I should probably get some different gear lube:

According to this site: http://www.wjjeeps.com/service/maintenance_wj.htm

I need either Thermally stable SAE 80W-90 gear lube or SAE 75W-140 synthetic if I tow. I do tow some, but not very frequently. When I got there, I had looked at so many numbers I couldn't remember which I needed. When he looked it up, he was seeing the same numbers but synthetic for both. The only specific match we could find was Royal Purple 75w-150 synthetic at $22 a 32 oz container.

Considering the idea that I may be getting this open and finding some problems in the differential, and then closing her back up and getting her to a shop, I don't think it'll make sense to put in top quality oil if it's only going to get dumped out a week or so later. So I'll probably grab some cheaper 80w-90 at $8 or so per 32oz as a backup in case things are screwed and I need to get the differential fixed.

Whatever the deal is, I'll be prepared to work on it tonight or this weekend, and depending upon what is found, will determine what fluid gets thrown back in there. Oh the fun this vehicle has become.

 

[ViviTheMage]

Yeah, I ran into the same thing when I was figuring out an issue with my rear dif...my personal preference is to always put in the same, if not factory lube ... so I used mobil 1 80w-90, as I towed maybe once or twice a year...but sounds like royal purple is a-ok :

http://www.jeepsunlimited.com/forums/showpost.php?p=4612226&postcount=15

you could read that thread too, good info.

 

[mvbighead]

Yeah, I ran into the same thing when I was figuring out an issue with my rear dif...my personal preference is to always put in the same, if not factory lube ... so I used mobil 1 80w-90, as I towed maybe once or twice a year...but sounds like royal purple is a-ok :

http://www.jeepsunlimited.com/forums/showpost.php?p=4612226&postcount=15

you could read that thread too, good info.

Yep, and the only reason I won't throw the royal purple in there is if the diff is all screwed up. If it looks bad, I'd rather slap some cheap stuff in there and get her to a shop to get fixed.

But, it does look like the royal purple will be fine if the diff is fine. From what I've seen around, royal purple is actually some pretty good stuff, hence the hesitation of throwing that it in just to get the fluid swapped out again.

 

[ViviTheMage]

If you were in the minnesota ... I could run an analysis on your dif fluid if you wanted, see what particles are in it.

I think someone did a test on royal purple and found it pretty good, comparable to mobil 1, correct me if I am wrong though...I don't recall the link for proof.

 

[nerp]

Royal Purple is controversial. Some will say your engine will be dead in 20,000 miles. Others say it will let it run for 20 million.

 

[iamwiz82]

Is the sound when you are accelerating or decelerating? If it is your diff itself it's cheaper to just swap in a used axle than to mess with the existing. WJ diffs are almost worthless on the market so you can get them very cheap and there is less labor involved.

 

[mvbighead]

Is the sound when you are accelerating or decelerating? If it is your diff itself it's cheaper to just swap in a used axle than to mess with the existing. WJ diffs are almost worthless on the market so you can get them very cheap and there is less labor involved.

I had actually read something like that somewhere. But another consensus seemed to be that used anything in terms of differentials was a bad idea because they apparently aren't the most reliable in jeeps, so you could just be buying something in the same condition or worse that what you have.

I dunno, I intend to swap the fluid today and see where it's at. Maybe I get lucky and it's fine and I just need a wheel bearing or two. Or, maybe it's fubared and I take it somewhere else to have it be their problem.

I'd like to do the work myself, but at this point it is my #2 DD and I can't be without it for too long. If I have to pay it out, I at least get a warranty out of the deal.

 

[mvbighead]

Got it done. Doesn't appear to be the differential, as there was just minor metallic dust caught on the magnet. The teeth seemed to be just fine to me, but then again, I may not know what bad looks like, but they didn't look bad to me.

On to wheel bearings maybe? Had trouble spinning the wheels as it's AWD. Putting the transmission in Neutral and the 4wd in the neutral didn't seem to change that much, as the drive shaft was still engaged. What am I missing here?

 

[allanon1965]

the noise you are hearing is caused be the ring and pinion gears, they wear terrible on the jeeps the big tipoff is that it changes under acceleration and deceleration.

i have 2 differentials in the shop now doing exactly that, one is a 35th anniversary edition camaro and the other is a 03 explorer. in both cases the gears have striation marks on the gear faces, difficult to see when in the case unless its real bad.

the particles you found dont look bad to you, but they are enough to cause the issues when caught between the meshing teeth of the ring and pinion gears. that is why EP lube(extreme pressure) is required for differentials. that material is coming from the bearings and races, which you cannot see until its torn down.

have it rebuilt by someone who knows how and is well practiced in the procedure as a few specialized tools are required to do it CORRECTLY. You can do it by the hillbilly method but it may not last long, although some get lucky.

the better option is to install a jasper rebuilt that will carry an excellent warranty and have any updates installed to assure a long life.

In our case, the camaro is getting a jasper rebuilt for 2300 installed with a 3year 100,00 mile warranty, the explorer i am rebuilding for 1900 and a 1 year 12,000 mile warranty. my own personal opinion is the dude with the explorer is an idiot...400.00 buys a much better product and better warranty.

 

[5150MyU]

You have 6 bearings back there.
2 on the pinion,2 on the ring gear, and 2 at the end of the axles.
You have 4 spider gears.
So between ring/pinion,bearings,and gears you have 12 items that can fail.

 

[5150MyU]

Sorry 14 if you include the ring and pinion.

 

[mvbighead]

the noise you are hearing is caused be the ring and pinion gears, they wear terrible on the jeeps the big tipoff is that it changes under acceleration and deceleration.

i have 2 differentials in the shop now doing exactly that, one is a 35th anniversary edition camaro and the other is a 03 explorer. in both cases the gears have striation marks on the gear faces, difficult to see when in the case unless its real bad.

the particles you found dont look bad to you, but they are enough to cause the issues when caught between the meshing teeth of the ring and pinion gears. that is why EP lube(extreme pressure) is required for differentials. that material is coming from the bearings and races, which you cannot see until its torn down.

have it rebuilt by someone who knows how and is well practiced in the procedure as a few specialized tools are required to do it CORRECTLY. You can do it by the hillbilly method but it may not last long, although some get lucky.

the better option is to install a jasper rebuilt that will carry an excellent warranty and have any updates installed to assure a long life.

In our case, the camaro is getting a jasper rebuilt for 2300 installed with a 3year 100,00 mile warranty, the explorer i am rebuilding for 1900 and a 1 year 12,000 mile warranty. my own personal opinion is the dude with the explorer is an idiot...400.00 buys a much better product and better warranty.

Well this is definitely what I didn't want to hear. Guess it'll be going to the shop. If this stuff really is going to cost upwards of $2000, I don't know how much interest I'll have in getting anything done to it. More likely an unload and get something else, as the vehicle is only worth a good 4000-5000.

For some reason, I was under the impression a rebuilt rear end would be in the sub 1000 ballpark. Grrrr. Not what I wanted to hear at all.