Well, on my way to work this morning, pulled up to a traffic light and heard this aweful metal grinding noise. Thought I lost another rear driveshaft ujoint but turns out the bearings in the rear end went. Fortunately, the gears seem ok but there was metal shrapnel everywhere. The bearings spun in the housing and scored it up a bit but looks salvageable. I have 96k miles on the truck. Is this typical for them to go out this soon? What are some reasons for the rear end to go out?

Sorry. This should be under '03-'07 3rd Gen.

 

I've heard of guys running 800+ on the stock rears. I've got 140000 on mine and everything still looks brand new. I think changing the fluid frequently helps

 

Yeah, it seems really odd to me that they went already. I change the rear end fluid every 30k miles with Mobil 75/140. The truck has maybe 50k miles of towing on it, and I don't tow more than 8k pounds. It's not like I'm running high horsepower or hot rodding the thing either.

 

i think it asks for 75w-90

 

Finished the rear end rebuild last week with all new bearings. Now running Mopar 75w-90 with an additive per dealership recommendation. Seems alot quieter and no more rear end clunk.

 

yfz,

Oh no, another "additive" discussion. Why did the dealer recommend the additive in AAM axles?

I know somtimes it is used to help stop chattering, but were you having that problem? Does the dealer think the 75w-90 is not good enough?

 

I have no idea why they recommended it and they don't either other than they said it "Calls for it". I called 2 different dealers and one said to use it and one said it wasn't necessary. I was also told to use it by a local truck repair center. I didn't think it was necessary but couldn't come up with any reason not too except for making my wallet lighter..... I figured, I just spent about a grand to fix the rear end, what's a few more bucks for an additive

 

2 guys I work with both have had rear end failures, but both were 1500's....

 

I believe the reason we don't need an additive is because we have this limited slip setup http://www.aam.com/index.php?s=49&item=99 as opposed to having this one http://www.aam.com/index.php?s=49&item=98 (used in GM trucks), someone correct me if I'm wrong here. Also, I believe it is also stated in the owners manual and service manual no friction modifier required.

 

Correct, gear type limited slip not clutch type. No additive needed as stated in manual.

 

Make sure you check the torque on the carrier caps each time you change oil.

My dually done this (spun bearing) The cap bolts were sure not 200 lbs. More like 25 ft lbs.

Had to replace the entire rear diff. Not a cheap fix. Was using amsoil then 75-90. It had turned to tar from the heat. Now running mobil 1 140 syn. All well now.... 140k miles in this rebuilt diff now. Put on a ATS cover and almost doubled the oil capacity. Sure is expensive to change now though.. 8 quarts. No more amsoil for me. Just wasnt impressed having to use a putty knife to get the fluid out of the obviously overheated differential.

 

I'm a firm believer in heavier weight lube in diffs and filling up to the axle tubes in these trucks when used hard. I think 75w90 is entry level for diesel P/Us, only good for light towing. Craig

 

Your prolly right on Craig. Amsoil trys to tell us we will get better mpgs if we use thin oils. Dont think it works if you are pulling fairly heavy. I'll stick with 140 from here on.

 

I just swapped my 3.73s for t 3.42s. My rear left carrier bearing was in real good shape; however the right carrier bearing was on the way out. The outer race was fine, however some of the rollers had pitting and the inner race was disintegrating. I bought the truck with ~40k on it and it has ~70k now.

I think that bearing had a manufacturing/metallurgical defect. It was a “KOYO” bearing. I needed to get the truck back together so I replaced them with SKF bearings from NAPA. I would rather have used Timken, but no local stores had any.

I don’t tow heavy and don’t know when the damage started or how long it would have lasted. I couldn’t see the issue until I took the carrier out and still didn’t know how bad it was until I took the rollers off the inner race.

When I bought the truck I changed the diff oil and replaced it with Valvoline (75/140 I believe). The oil that came out may have been the factory fill. I ran than for a while and put in Amsoil 75/110 until I swapped the gears. I broke the gears in for 700 miles with Valvoline 75/90, and then replaced it with Amsoil 75/110.

I’ll also mention that when I bought the truck it had the paint burnt off the rear diff cover. During my 700 mile “break in” I monitored the diff temp (when I fuelled up) with a temp gun and saw anywhere from ~175F on the rear cover surface—not enough to burn the paint off. I think that would take heavy towing.

 

I had a D80 in my 97 that ran 280+ in the summer, towing hard. I bought the truck new so I know it was never run low or missed any maintenance and RP 85w140 was the first lube I found (after trying different brands and working up in weights with the RP lubes) that would keep the wear crud from building up on the magnet and give me good UOAs so I've stuck with it. I lived in the Denver area then and saw NO decrease in mpg after using any lighter lubes including Ams 2k 75w90 which BTW was the worst lube I tried i.a.w. wear metal on the magnet and poor UOAs. Craig