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I am getting ready to change out my rear gear oil and after doing research one of the better rated oils is Mobil 1 75w90 with limited slip friction modifier added. Amsoil is the best but is harder to find and costs about what the Mopar oil does. (Mopar oil was not rated that high). See comparison chart which was produced by Amsoil so is obviously biased to their product but rates Mobil 1 as second place.
https://www.lastgreatroadtrip.com/wp-content/uploads/2010/11/gear-oil-comparison.pdf

My question is whether or not anyone else has used this Mobil 1 synthetic oil and did you need to add additional friction modifier? The owner's manual says to add 5oz (148ml) of Mopar friction modifier (even though they only sell 4 oz bottles, misprint??) but that of course assumes you are using oil without modifier in it.

I have seen a different answer each time I look regarding the use of the Mobil 1. Some add about 2oz of modifier, others add none, some put 2 bottles of modifier in. Hence the reason for my post.

I might just pay out the nose for the Mopar stuff adding friction modifier or get the Amsoil product and add a bottle of modifier.

Hopefully, some real world insight from someone who changed out their diff fluid.

Thanks
 

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I did some more research and have somewhat answered my own question for now and figured I would share what I learned and let others decide for themselves on what gear oil to use. I am going to use the Mopar 75w90 gear oil, 68340460AA (3 bottles 2.2 quarts to fill dif) and then add Mopar friction modifier, 04318060AD (5oz, requires you to buy 2 bottles, only 4oz)

In 2017 RAM apparently changed something in the rear end on the 1500 and now calls for completely different 75w90 gear oil that was not easy to find and can be found on page 30 in the attached link and has the following part number, 68340460AA, and meets the MS-A0160 spec listed in the 2017+ owners manual. The other Mopar 75w90 gear oil you will readily find online is MS-9763 (there is another 75w90 for the 2500/3500 as well), which is not the correct gear oil for 2017+ RAM 1500's. Not confusing or anything :)

RAM 1500 trucks prior to 2017 called for Mopar 75w140. MS-8985. This was a GL-5 spec like the Mobil 1 I mentioned in my first post. This new Mopar MS-A0160 spec was very hard to find and not until I stumbled upon this Mopar chemical list did I get a part number and see this was an entirely different gear oil specd for 2017+ 1500 trucks. I don't know what the new spec is and how this oil is different form Amsoil, Mobil1, Royal Purple, Valvoline, etc. variations of 75w90 with LS modifier already added.

Has every chemical Mopar uses with part numbers:
https://www.dealers-mopar.com/resources/pdf/chemical/chemical-catalog.pdf

To make this easier for anyone with a 2017+ LSD here are part numbers for a diff fluid change including proper RTV sealant for diff cover (if you decide to remove it) and rubber fill plug if yours is damaged:

04318060AD Mopar Limited Slip Additive 4oz (need 2 bottles to get 5oz)
68340460AA Mopar 75w90 Synthetic Gear Lube 2017+ C235 axle MS-A0160 (3 bottles needed, diff takes over 2 qts.)
52070428AA Differential Cover Plug (Needed if your fill plug is damaged)
5013477AD Axle RTV Sealant (Needed if you remove cover)
14mm hex socket for drain plug on right lower side of pumpkin. (24 ft/lbs on reinstall, not confirmed)
Finding diff cover bolts get torqued to 30 ft/lbs. I would go less than that 20 ft/lbs or so should be more than enough (if cover removed)

Hope this helps anyone who might have similar questions. There are a boat load of opinions out there on gear oil.
 

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Anyone know if Redline or Amsoil 75w-90 will work in place of the mopar fluid? Or am I better off sticking with the oe fluid.
2017 Ram 1500 w/ c.235 rear axle.
 

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Anyone know if Redline or Amsoil 75w-90 will work in place of the mopar fluid? Or am I better off sticking with the oe fluid.
2017 Ram 1500 w/ c.235 rear axle.
Hard to say. I looked up the Redline 75w90 and it listed the MS-9763 spec which is the older Chrysler 75w90 listing. I could never find what exactly the MS-A0160 spec was for Chrysler's new 2017+ 75w90 (click on the Mopar fluid link above to see). Therefore, I just went with the factory oil. Honesty, I am sure you will be fine if you used Amsoil or Redline. I was being overly cautious and went with the factory stuff because I tow a 7700 lb travel trailer with it. What I can tell you is buy a replacement rubber plug that I listed above. Once I removed the old one and reused, it leaked. Put the new one in and good to go. They are apparently one and done.
 
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