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Discussion Starter #1
My '08 had developed a vibration with humming noise in the rear area at highway speed 60mph and up. It's driven me nuts over the years.
Just also add that I'm a very experienced BMW / Porsche technician by trade and have 4+ decades of under hood time. We've owned it since it
had 29K on the clock and have performed a few mods and continued good maintenance. For some reason around 60K a slight vibration started in the
drive line, over a long period of time slowly got worse.

These SUV's ride, handle really well and make great highway cruisers...……...when everything is in order. So when I had time I did all the usual
stuff - inspected from bumper to bumper, had 2 wheels that were a little out, replaced all of those along with new non-run flat tires
( thanks to everyone here for that suggestion) checked front and rear wheel bearings / play, on and on. I knew I had to pull the front and rear shafts
to check but never seemed to have enough time.....until recently. BTW, this is my wife's DD.

I know that there have been many members here who have gone through the same thing over the years. I researched again and again but could not
find 1 common solution...……….until recently. I happened to find a bulletin from the factory specifically addressing this complaint. Turns out that
the grease that lubricates the male / female splines creeps out of the slip joint over time and collects into the accordion boot crevices. The grease starts
to pool by centrifugal force and that localized pool of grease creates enough weight to cause the issue!

So this past holiday I had enough time to remove it, disassemble and to also check the joints and companion flanges. Sure enough I found a small
pool of grease in the protective boot. I cleaned it all out, checked the joints and then found rear one was just a tad notchy, which is fine for now.

I cleaned all flange mating surfaces and reinstalled then went for a test drive at highway speeds. It's almost completely gone; both the noise and vibration!
I suspect that the rear joint is the last 10-15% of that to be perfect. I know that with 170K on the clock now, I'll have to pony up for a new replacement
rear shaft in the future at @$900.00 - but at least for now I fixed it.

I hope this thread helps members here that area experiencing the same thing. I have actually seen / read where people bought a new Mopar driveshaft
and it fixed their problem but didn't know why. Now you do!
 

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Turns out that
the grease that lubricates the male / female splines creeps out of the slip joint over time and collects into the accordion boot crevices.
Great write up. The mystery is finally solved! I know if I ever has this problem I'll know where to look now.
 

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Do you have a link to the factory bulletin handy?

^ that is the only bulletin that I could find, which specifies the WH export model with an NVG 245 transfer case. Regardless this has been an ongoing issue with these jeeps. I remember the old '98 5.9 ZJs would experience the same humming, but that was due to the gears not being shimmed correctly in the case. Some were too tight, others had excessive play/slop. Don't quote me, but I think the WK1 SRT8 also uses a very similar dana rear end, if not the same one.
 

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My '08 had developed a vibration with humming noise in the rear area at highway speed 60mph and up. It's driven me nuts over the years.
Just also add that I'm a very experienced BMW / Porsche technician by trade and have 4+ decades of under hood time. We've owned it since it
had 29K on the clock and have performed a few mods and continued good maintenance. For some reason around 60K a slight vibration started in the
drive line, over a long period of time slowly got worse.

These SUV's ride, handle really well and make great highway cruisers...……...when everything is in order. So when I had time I did all the usual
stuff - inspected from bumper to bumper, had 2 wheels that were a little out, replaced all of those along with new non-run flat tires
( thanks to everyone here for that suggestion) checked front and rear wheel bearings / play, on and on. I knew I had to pull the front and rear shafts
to check but never seemed to have enough time.....until recently. BTW, this is my wife's DD.

I know that there have been many members here who have gone through the same thing over the years. I researched again and again but could not
find 1 common solution...……….until recently. I happened to find a bulletin from the factory specifically addressing this complaint. Turns out that
the grease that lubricates the male / female splines creeps out of the slip joint over time and collects into the accordion boot crevices. The grease starts
to pool by centrifugal force and that localized pool of grease creates enough weight to cause the issue!

So this past holiday I had enough time to remove it, disassemble and to also check the joints and companion flanges. Sure enough I found a small
pool of grease in the protective boot. I cleaned it all out, checked the joints and then found rear one was just a tad notchy, which is fine for now.

I cleaned all flange mating surfaces and reinstalled then went for a test drive at highway speeds. It's almost completely gone; both the noise and vibration!
I suspect that the rear joint is the last 10-15% of that to be perfect. I know that with 170K on the clock now, I'll have to pony up for a new replacement
rear shaft in the future at @$900.00 - but at least for now I fixed it.

I hope this thread helps members here that area experiencing the same thing. I have actually seen / read where people bought a new Mopar driveshaft
and it fixed their problem but didn't know why. Now you do!


OP, this is awesome info - I have the same symptom on my 06' w/ 85k miles and just couldn't trace the source.

So that I can better visualize exactly what parts/areas where you're referencing the problem exists, can you lay out in more detail? IE -

... are the splines you referencing on the rear driveshaft? which end of it, transfer case or rear diff? Is the boot sealing the whole union area, so we'd have to remove/replace it to clean out the grease? Could you shoot a picture if you could throw yours on the lift at work?
 

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Discussion Starter #7
Hi all - if you go to YouTube - enter Grand Cherokee drive shaft vibration - there is a guy explaining the problem- then showing the grease pooled in the boot.

BTW - all late model GC & Comanders have this type drive shaft - but there are 2 different lengths.


Oddly enough, Googleing something rarely takes you to youtube even though Google owns youtube.
 
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