Recently acquired a 2008 Aspen 5.7 Hemi AWD with 146K miles. Previous owner was a reasonable maintenance guy so he kept up on things. I was told the transmission, front and rear differentials and transfer case were all serviced recently. The transmission fluid looks great and smells correct. The diff covers do not appear to have been off in recent history. Specifically the rear is my concern. The threads on the watts link bell crank show it has not been off for a long time or ever, so if it was serviced it must have been sucked out. I cannot find fluid in the fill hole with my finger and the pinion seal has been slinging fresh fluid on the under carriage. The U-joints in the driveshaft appear to be original but I cannot find any slop.

At slow speed, when I engage and left off the throttle moderately, I can get a driveline clunk. I will start by saying the front end is fresh and tight as are sway-bar end links. The MDS has been disabled in the ECM. When inspecting underneath, I can rock the driveshaft back a forth by hand and the differential seems to have more rotational movement than I remember my Silverados or Rangers having, which are my only other solid rear axle points of reference. I have no whine or grinding. How much play is acceptable? Could this be my clunk? How robust are the Chrysler rear diffs? I also inspected front driveshafts and prop shaft and they appear in good order as well.

My next step is going to be to remove the rear diff cover, drain and inspect. If the surface of the ring and pinion teeth look OK and/or I don't find lots of metal shavings or gray mud, then replace the pinion seal and refill/reseal the differential. Since the driveshaft will be out, go ahead and put some Spicer greaseable joints in it . I typically use Mobil 1 synthetic for gear oil. What viscosity fluid should I use and do our trucks need a friction modifier? On that note, what lube should I use in the front diff and transfer case as well? I plan to inspect those and if the fluid is remotely iffy, I will change it too.

I did do some forum searches first and mostly found old discussions about the low service intervals for the diffs just being a dealer money maker. Any suggestions would be greatly appreciated. Thank you.

 

Answering the questions I do know.

Front Diff Fluid - 75W-90 gear oil. 3.4 pints. - No modifier.
Rear Diff Fluid - 9.25 Ring Gear - 75W-140 gear oil. 4 pints. - **4 oz. of Mopar Limited Slip Additive (MS-10111)**. I just picked up some additive at my local Autozone.
Transfer Case - ATF - ** 1.9 pints for NV144 or 3.4 pints for NV244 **

Sorry I can't help you on the rest. I swapped out all fluids when I got mine a few years ago and I used the Amsoil site for info when I did it.

 

Thanks for the fluid info. Did some of our trucks come with Limited Slip? I have not had a chance to tear into things but I did inspect a little more. It appears I have the 8.25IN 10 bolt rear differential with a bellcrank attached to the differential cover that connects the watts links. When I have the vehicle on the lift, I can turn one rear wheel forward and the opposite wheel turns backwards. I have always believed this to be the behavior of an "open differential" vs. limited slip or posi. When I pull the cover, I should be able to see if the differential has springs/clutches like a limited slip.

Any benefits OR negative results if friction modifier is placed in an open differential?

Still hoping to find input from somebody on how much play is acceptable and if it can be shimmed or adjusted.

Thanks,

 

Been a couple of weeks. Anybody have info on how much play or movement is acceptable for the rear axle?

 

I hate to say it, but this forum does not get much activity. Especially since the Aspen was only made for 3 years so theirs not a lot of us out there. You might want to look in to a Dodge Durango forum. The Aspen was built on the same platform as the (2nd Gen). Just some minor tweaks here and there. Mostly in the body lines. You might get more input from members of the Durango. Two that I monitor:
https://dodgeforum.com/forum/dodge-durango-22/
https://www.dodgedurango.net/

 

I have the same clunk, '08 5.7 4WD, 176K... I bought it with 135K, and noticed it pretty early on.

On acceleration from around 10-12 mph. It's not bad, but noticeable, like someone is kicking the seat behind you.

Chrysler did issue a TSB a few years back (google:18-006-10 REV. B)

I tried a few things..I've replaced the shocks, flushed the transmission, had front and rear differential serviced, replaced the transfer case motor, and did this TSB (had to pay an hour of labor), and nothing has really solved it.

It has not gotten better or worse, and not noticing any other issues, so I'm just going to live with it for now, but curious as to what it could be.

 

Thanks for the info. I am coming to the point of living with it... The TSB doesn't apply as I have the MSD tuned/off.