I just changed my Rear End Fluid Sunday and noticed that the fluid that came out was thinner than what I put back in. I used Amsoil 75W90. What kind of fluid is used from the factory?????? Does anyone know? I had 35,000 miles on it with some pulling but not much. Old fluid wasn't to bad.

 

I recently brought my truck in to see what could be done to reduce rear axle whining. Aside from finding a bent axle, which immediately got my attention, they did confirm that the differential was fine. Whiny but fine. However, the tech working the repair mentioned that there was a service advisory that discussed the issue of rear axle heat, wear etc. The advisory recommended that heavier 75W-140 sythetic gear oil be used for any truck that is used for towing.

Afer all was said and done, even with the heaver gear oil, the differential continues to whine away. Apparantely whiniing differentials are not uncommon. However, determining when the level of whining reaches the point where the dealer will agree to replace the ring and pinion is another story.

 

The axles are filled prior to being shipped to an assembly plant, you might check with American Axle for their fluid specs.

 

If mine was whining, I would double check the backlash and wear pattern myself. You can get a Dial Indicator and magnetic base from Harbor Freight for about $30. Then spend an hour for peace of mind. It's not that I don't trust the dealer, but... Who am I kidding? I don't trust the dealer.

 

Ramstang I was just on another site and a reply I got was the units are shipped without fliud and D.C. fills them?Was also informed about the advisory about the 140 weight with a liminted slip "modifier". But I just talked to AAM the other day and they said don't use a modifier and no one has of yet seen anything about the 75w140 weight or modifier in print.All I'm saying is Who's right and who is just shooting from the hip? I've got a terrible shudder from my rear diff after towing 9k at interstate speeds for a few hours and searching for the correct answers.

 

All I know is the fluid that I drained wasn't as heavy weighted as I put back in and I put Amsoil 75W90 Severe Gear lube. It was the Factory fill whatever that is. I had no shudder after pulling 2 1/2 hours at 70 MPH. I haven't pulled far enough to know how it is going to do now. Both fluids were at the same temp. Pulled the truck into the garage and changed it. Very curious........I hope I don't get the studddddddd, shudder.

 

I am also.I knew for years that what we drained fron Nissan manual trannys was thinnn.Service manual called for 75w90 but that brought on LOTS of complaints about hard shifting cold.Finally found out the factory fill was straight 75wt.Took like 5 years to get the darn correct answer.I hate to think THIS will take that long,LOL

 

I just changed mine, put mobile one 75-140 M ?? something 5 rated, said was good for lsd & it was what was called for. The Lube looked really black, and only had 8000 miles. Probably was a waste of money, but I did it anyway, I had no whine or problems. But man that fluid was black and funky looking. I don't know what they fill it with. My luck probably was already synthetic and I just wasted my time and money. Oh well, guess I'll do the front this weekend.

 

GL-5 rated synthetic 75-90.

 

AAMs like 75W-140 in the rear diff for towing or hauling.

jerryk - how the heck did ya bend your axle on that new truck?

 

If the '06 shop manual is any indication, it looks like the factory fluid is Mopar Synthetic Gear Lubricant 75W90 for the 10 1/2AA, 10 1/2AA EL, and 11 1/2 AA. The 9 1/4 calls for Mopar Synthetic Gear Lubricant 75W 140, and the 248RBI uses Mopar Gear & Axle Lubricant SAE 90.

 

I just did my rear diff the other day. (truck is an 06 with 18k on it) When I pulled the plug, fluid actually started to drain out a little. When I pulled the cover and drained the fluid it was really foamy. The fill line stamped on the cover is about a half inch below the plug. Is this normal or was it over filled from the factory? I can't see foaming being good for lubricating the bearings. My fluid also seemed to have a lower viscosity than 75w90, and it smelled like strawberries.
Also, JERRYK how did you bend an axle ? Those tubes are really heavy duty and the axle shafts themselves are full floating axles. It would take one heck of a blow to bend one...

 

Couple of points. In my earlier post I mentioned the use of 75w-140 gear oil for vehicles that tow. The basis of using this oil is from a Dodge service advisory. I have a copy of the advisory, unfortunately its sitting in CO and I'm sitting in MA.

As to the bent axle. I tow with a combined weight of 19,000lb give or take a few. Discussing the issue with the two techs involved with the actual repair, the service manager and my fleet sales rep here is what I was told. Could have been a factory defect. This was the choice that the dealer used to replace the axle under warranty. Great news for me. The second possiblity was is an accident, in my case it was pretty obvious that the truck has never been in one. Another factor that the dealer used to cover the repair . The third is actually the most common event that will bend an axle. Off roading and getting into a situation where one of the rear tires gets off the ground and then suddenly drops and is subjected to tremendous loading. In my case my off roading is pretty limited, nothing agressive.

During my discussions the question of durability of the rear end came up. I was ready to trade the truck for a 3500. However, the tech told me that my truck had the same 11.5" rear end as the 3500. Naturally I was a bit skeptical and decided to pull that thread a bit. I went over to the parts department had them pull up the parts list for the 3500 rear end and jot down the part numbers of the axle and hub bearing (this bearing carries the entire load of the rear end). We then pulled up the part numbers for the 2500.Well the tech was right. Part numbers were the same. This was pretty much confirmation of something that I had beleived all along but sill had a bit of lingering doubt. The 2500 and 3500 areidentical except for the overload springs on the 3500. Thus, with the addition of the appropriate overload springs on the 2500 (I use Firestone air bags) it can handle the same load as the 3500. Please spare me the urban legends about being stopped and having the GVWR verified by some manevolent entity. Ive been RVing for the better part of 30yrs traveling coast to coast and never even seen a check point that was looking at RV loads. Trucks U bet.

 

What is the reason of the 75w140? A friensd of mine just drained his(he is a master tech of another brand) at 35k for the first time.Said fliud looked good and WAS NOT any where near as thick as what he put in(80w90 Amsoil) I did find a old post by MAD DUC in the 6 month describing the very same shudder I encounted and said it was cured by the 75w140.So far from the manufacture or any aftermarket group there is no mention of using 75w140.All thats in print says 80w90 etc.

 

I have forwarded your post to the elite national weight police unit that inspects door stickers on 2500-model trucks for GVWR compliance. It's a dangerous job, but they're well-trained. They practice on the range with Hello Kitty stickers so no one gets hurt.