Rear end whining on power - How to diagnose cause?

[WheelNut]

Hi folks,

My KJ has been making more and more noise from the rear axle over the last year. The noise is audible only when on power and does not change with cornering or steering. The service manual indicated that this is caused by a bad pinion bearing. What more can I do to diagnose this issue? Perhaps it is just a wheel bearing somehow, or a U-joint in the driveshaft, or maybe something else?

I spoke to a driveline shop around the corner from me last week and they estimated about $1500(CDN) to replace all the bearings and seals in the rear axle. The axle shafts, diff and pinion all need to be removed to replace the pinion bearing as far as I can tell, so its a real 'while your in there' kinda job. Sounds like they've done quite a few Chrysler 8.25" axles over the years so he knew the routine pretty well. Here's the rub- this Jeep is only worth $5000 at a push, so spending 30% of the vehicle's value to fix up the rear axle is a bit illogical. The other option would be to install a complete used axle, which should save me quite a lot of money, but with no real guarantees of long life, but I only drive the KJ 10,000km (6,000mi) per year, so its not getting mile'd out anytime soon.

 

[The gov]

Hi folks,

My KJ has been making more and more noise from the rear axle over the last year. The noise is audible only when on power and does not change with cornering or steering. The service manual indicated that this is caused by a bad pinion bearing. What more can I do to diagnose this issue? Perhaps it is just a wheel bearing somehow, or a U-joint in the driveshaft, or maybe something else?

I spoke to a driveline shop around the corner from me last week and they estimated about $1500(CDN) to replace all the bearings and seals in the rear axle. The axle shafts, diff and pinion all need to be removed to replace the pinion bearing as far as I can tell, so its a real 'while your in there' kinda job. Sounds like they've done quite a few Chrysler 8.25" axles over the years so he knew the routine pretty well. Here's the rub- this Jeep is only worth $5000 at a push, so spending 30% of the vehicle's value to fix up the rear axle is a bit illogical. The other option would be to install a complete used axle, which should save me quite a lot of money, but with no real guarantees of long life, but I only drive the KJ 10,000km (6,000mi) per year, so its not getting mile'd out anytime soon.

Just my two cents but a used rear end while cheaper and may sound like a great deal it's still going to cost to install unless you are doing it yourself, a rebuild of your own rear diff while more expensive is a once and done deal...
But are you sure that it's the diff? I just did a friend's liberty last year he thought it was the rear diff but when I did some investigating it was his double cardon yoke, simple rebuild kit and end of his rear end noise. This is just a suggestion but it might save you time and money.

 

[WheelNut]

Yes, I know its possible it could be something else. How do I start to diagnose if it is a drive shaft though?

 

[The gov]

Yes, I know its possible it could be something else. How do I start to diagnose if it is a drive shaft though?

Take it for a 10 minute drive than feel the universal joints if they are mildly warm that's normal if they're hot that's a good indicator of either lack of grease or a worn out universal, do you recall having replaced any universal joints if not they maybe washed out and have no grease in them causing the needle bearings to have crushed and turned to powder, unless you have run that rear diff without oil they are a tough unit and 100,000 klicks is not really many kilometers for the year of your Liberty.

 

[duderz7]

Put rear end on jackstands, block front wheel securely, then block them some more, start it, put it in drive, and see if you can't tell where the noise is coming from. A mechanic stethoscope would be helpful. Pinion bearing would be heard at the front of the pumpkin just behind the drivshaft yoke. It could be as simple as needing an e-brake adjustment.

 

[WheelNut]

Duderz7. The danger man hahah. Okay, thanks for the tips guys. I’ll give the Jeep a drive and see how warm the joints are. If they arent hot I’ll get my blocks out and give Duderz7 suggestion a try.
Oh, just a note- My KJ has 230,000km on it (130,000mi).

 

[WheelNut]

Took ‘er out for spin. No heat in the U joints. A small amount in the axle near the pinion and a tiny bit of heat in the diff pumpkin.

 

[derekj]

Personally - I would go for the rebuild instead of a used assy - buying used is a bit of a dice roll, you could be golden or get a worn out diff that never had the oil changed. I like to just do the job once - hate doing a job over because someone wanted used parts installed.

Is the noise a high pitch whine? If so that will be the pinion bearings - like duderz said best way to tell is get it up on a hoist and run it in gear while listening with something.

 

[Big Al]

When I acquired my 2003, it came with that high pitch whine and growl when accelerating. Take off the gas and it was quiet.
So I opened the diff cover and sludge poured out with metal shavings.
Also the spider gears were pitted and chunks missing from them.
Fresh oil and sealed it up, still have the same noises.
Mine is a posi traction rear end and that works well on snow and ice still.
I’m in s the same boat as you, just run with it as it is a costly repair.
Was thinking of doing a second oil change to see how bad the oil got over a 2 year run.

 

[Ksat]

Next time you go down there, grab on to the pinion input shaft just to see if there's any lateral movement in it. Have you checked the gear oil level in the diff, BTW?

You might want to invest in a ChassisEAR tool, which has microphones you can clamp on to different areas back there plus a headset so you can listen on the noises. You switch between the mic channels as you're driving and determine where the noise is the most pronounced. The tool is about $100, though there are knock-off versions which can be had for less and probably work just as well.

Replacing the U-joint back there might be a good 1st step before signing up to replace the axle internals, just to rule out that being the cause. The part is usually less than $20 and pretty easy to replace.

 

[Shankster]

I had similar symptoms on my 02. I had my wife drive me around while I crawled around in back with my ear to the floor till I narrowed in on the diff. Turns out my problem was a sheared pinion shaft pin. I bet I could have replaced the pin and been good to go. I had purchased all the parts for a Torsen LSD install though before I dug in. I'd recommend pulling the cover off and doing a fluid change and have a poke around in there to see if you have a similar problem to mine that might be a simple fix. A Torsen is a nice upgrade, especially if you go 4wheelin occasionally or drive on snow much so it might make the cost a bit easier to swallow if you're getting a worthwhile upgrade. The Torsen itself was $500 but since you might need to replace factory open diff parts anyway the net cost may not be quite that bad.

 

[DeCaff2007]

Yup, went through this myself when the Wife had her first KJ. The rear diff was grinding like rocks in a tin can. Horrible.

I got lucky and found a rusted to death KJ in the yard - with rear drums. Ughhh.

Pulled the diff cover quick and the spider gears were luckily nice and shiny. Just had to replace the wheel seals and swap over to rear disc. Really NOT hard to do.

She ran that rear end until the cows came home. It actually outlasted the rest of the body on that Jeep.

 

[sota]

I hate the attempted calculus of "my vehicle is only worth $***" as a comparison against repair costs vs. replacing.
You need to factor in the maintenance you've done, the condition of all the other components in the vehicle, and the attempt to find one of similar/identical condition (sans the issue you're currently looking at.) Plus you never know if someone is attempting to pass off a total t.urd without disclosure.

EVERY used vehicle I've bought, has needed extensive maintenance/repairs in the first couple of years, some of them thousands of dollars in parts. Mileage has never been the factor that determines this; age is. But, I make sure to get said vehicles extremely cheap, so as to make the investment worth while. I usually buy them broken in some way that the current owner doesn't want to pay to get fixed. So when I drop $2800 in parts on a $900 vehicle, I'm in better shape than a supposed $3700 copy.

 

[WheelNut]

Thanks for all the feedback guys. Lots of really helpful stuff here. You folks are a real helpful group that is for dang sure!

I refreshed the rear diff oil about two years ago. So, it shouldn't be low as I can't see any leaks. I noted that there was a small amount of silvery-ness to the oil when I drained it back then, so I suspect the trouble started a few years ago before I bought the vehicle.