I did a search, but didn't find anything really informative. Maybe I didn't use the right terms.. I don't know.

Anyway, my rear end feels like it's always locked up.
I have a 9.25 axle w/ limited slip. My odometer is at 181,6XX.
This is most noticeable on slow speed turns. There is noise and vibration coming from the rear end- much like that you get when turning in 4wd. The transfer case shifter is in 2H and the 4x4 light off.
This has been happening for the past few weeks.
I think maybe the LSD clutch pack has worn out? I don't know much about rear diffs. I haven't pulled the cover yet because the oil is expensive up here.
My rear diff has made noise sense I bought the truck. It makes a loud humming noise when coasting, especially when turning right (when the truck's weight shifts left). The sound sounds like it's coming from the rear axle. Could this also be the LSD mechanism, or worn out bearings/gears?

Thanks for your ideas/input/help

 

Well.. I finally remembered to check the differential oil.
It was humming loudly while driving under load (used to only hum when coasting).
I popped off the plug and stuck my finger in- no oil within reach.
I put in a couple of quarts for now while I figure out how to fix the leak.
It appears to be leaking out of the seal where the driveshaft attaches to the diff. There is oil around there and running down the pumpkin. There is also oil sprayed around on the gas tank, bed underside, and exhaust pipe.

What is this seal called and how hard is it to replace? I have a Hanyes Manual, but I have no idea what that seal/part is called to look it up.
If I fix the leak and keep the oil level up, will the hum quiet down? It hasn't yet. Does this mean permanent damage has been done? I can not afford a new axle if this one is about to die.

 

Your pinion bearing is going bad. Mine only lasted about 500 miles after the first symptoms. You are going to need to get a new rear end. I found tons with around 100k miles or so for $100. It is really easy to swap out the only tricky part being the emergency brake.

The rear end will basically explode and send pinion bearings and diff oil everywhere. I know from experience.

It another one of those common dodge problems we are just supposed to live with.

 

Couple issues going on here, it sounds like. For one, that is your pinion seal that is leaking. On 9.25's, they often leak because the pinion nut has backed off. If caught early enough, just replacing the seal and retorquing the pinion nut will do. More on that in a minute. However, if you're already whining, it's probably damaged the bearing, and you need to overhaul the rear end. This is not something you should attempt yourself without help from someone who knows what they're doing.

Secondly, assuming the binding and chattering continued after topping off the fluid, the diff probably didn't get the friction modifier when the fluid was last changed. You can get it from Chrysler, or use BG LS2 from Napa (or whoever).

Now, if you decide to replace your pinion seal, be aware that there is no torque specification for the nut itself; These are crush sleeve pinions, so you have to set preload by measuring thrust. For used bearings, you tighten the pinion nut until it takes roughly 15 inch pounds of thrust to rotate it. This is kinda tricky with an assembled diff, as you are measuring that thrust using the backlash free travel; You will only be able to turn the pinion a few degrees back and forth before it engages the ring gear teeth, and that compounds the resistance, giving you an erroneous thrust reading and leaving your pinion preload too light. Also, loc-tite the crap outta that pinion nut. Apply it to the pinion shank as well. Red loc-tite.

Honestly, I would have a professional give you his opinion before proceeding either way. It'd be pointless to replace the seal if the bearings are toast. And if not, it might be worth it to pay a shop the $120 or so to do the pinion seal, since I'm guessing you'll have to procure an inch-pound torque wrench to do it yourself anyway; a cheap but decent one with an indicator bar (my preference for this task) runs about $50, then another $15 or so for the seal. To actually overhaul the diff, you'll need a hydraulic press and a good clamshell. And, of course, another torque wrench. One that's capable of 100 ft/lbs.

 

Alright. Thank you. I'll have a shop check it out.
This could be a problem as I'm supposed to drive down to Texas for Christmas.
I hope it's not worn bad.

 

^all that is correct, but since you filled it back up with oil -
is it acting and sounding right ?
or is it noisy and still binding ?

if its acting a lot better, then just replace the seal for the $100+
beware, a rear end rebuild will be pricey. another option would be to get a complete housing from the junk yard and replace yours. be sure the gear ratio is the same.

if its doing any better, then its critical that you keep it mostly full of oil.