Rear gear oil

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Joseph Godvin

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I think most Diff oil's are basically the same, the difference is in changing the fluid as recommended, and of course how the truck is used. I use Synthetic 85-140 in my Harley Dresser Transmission with great results.
 

Burla

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The good news is it is just a gear box, I wonder if you guys would chose your pace makers with the same feelings based analogies. Well, I think pace makers are all pretty much the same, go ahead and put the cheap on in :)
 

MontanaHandyman

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The good news is it is just a gear box, I wonder if you guys would chose your pace makers with the same feelings based analogies. Well, I think pace makers are all pretty much the same, go ahead and put the cheap on in :)
Like the ol' saying goes...if you buy the best, you don't look at the rest.
 
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RHanna

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I ended up using Valvoline 75w-140 and I added 4 ounces of the mopar friction modifier. It looks like the valvoline had friction modifier already in it but it didn't match the requirements from the manual. I used a lubelocker instead of rtv. I have lubelocker gaskets on the front and rear diff of my Jeep TJ and they seem to work just fine.

I don't think the cover had ever been removed and it was a ***** to take off.
 

Dusty

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study

Even though that study is old, it shows how little care goes into approving a fluid and getting the mopar name. The issue is it is always changing, but not for some staple gear fluids such as m1 or valvoline which have always been good, redline and amsoil as well. Those go the extra mile, m1 for otc or amsoil for boutique. Now, Mopar is most likely a Pennzoil clone, but also those didnt test well. I prefer to buy real quality if I can. Being on the 4x4 forums from way back since the beginning of the internet, two of the bottom three on the list are straight cus words on those boards from the amount of gear fails they are suspect in. In a truck application, I believe it matters way more then anything else. just my opinion...

I doubt the mopar additive is different then most others, but personally I would still use something else.

I just posted a favorable review on maxpro a mopar brand, because that formula looks good. I call it how I see it, on gear fluids I have NOT seen anything good from them. It is possible even Pennzoil is in the same quality as the other two otc currently, but their track record is still relevant, would you rent your house to a convicted felon if the other potential renter isn't a felon? m1 gear oils are even more standout then their engine oils.
I found the AMSOIL “Study” document interesting. The, “performance testing was conducted by an independent laboratory” and the “I hereby affirm…” witness signature normally identifies the organization as normal practice. Both are missing. The fact that the specific test criteria (D-97, four-ball, etc.) was done in house does not disturb me. Lubricant manufacturers rarely publish that type of test data, AMSOIL probably had no choice but to conduct their own tests to obtain the data points.

However, because manufacturers material formulations often change, any comparison evaluations from 2007 are potentially dated and may be inaccurate or totally invalid today. The reference to MOPAR Synthetic 75W-90 with Mopar LS Additive is a prime example. This is not a product listed in the 2020 or 2021 Mopar Chemical Catalog. It MAY have been marketed in 2007, but without a Mopar part number I cannot find any reference to it except in the AMSOIL document, and as far as I can tell it has not been available since at least 2010, which is as far back as I could trace.

In any event that product, if it existed, is no longer available.

My main point, however, is there is more than one current Mopar differential or gear lubricant, and most of these are recent, equipment specific, and represent a range of formulations. Just to cover a few: the one most common for DS and DT is the Mopar Synthetic Axle Lubricant SAE 75W-90 for select Ram 1500, 3.21, 3.55 ZF axles (68218655AC), or Synthetic Axle Lubricant 75W-80 for 3.92 ZF axles which meet GL-5, J2360, and MT-1 (68218657AA). Although not in the 2021 Mopar catalog, for those with the Max Tow 3.92 axle, Ram recommends Dana SAE 80W90 Axle Lubricant (68375248AA).

Then there’s Synthetic Gear & Axle Lubricant SAE 75W-90 (68218655AC) for AAM axles (DS). There’s a Synthetic Gear & Axle Lubricant SAE 75W-90 specifically for DR 2500-3500 AAM axles (68218654AB), a Rear Axle Lubricant SAE 75W-140 (68449547AA) which is pre-mixed MS-10111 friction modifier for DRW axles only, as well as a Mopar Synthetic Gear & Axle Extreme Pressure Lubricant (68378949AA).

Obviously there is not one universal gear lubricant for Ram/FCA vehicles.

I’ve included a PDF [http://weaverdist.com/docs/Mopar Chemical-Catalog 2021.pdf] of the most current Mopar Vehicle Lubricant & Chemical Catalog (2021), however I would strongly recommend Ram owners ask a Ram dealer by VIN which lubricant is specific for your vehicle.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33 gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 03 June 2018. Now at: 062993 miles.
 
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HEMIMANN

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Yeah, they're getting a bit ridiculous. Not sure what's going on out there with all this micro-slicing of gear lubes. Generally speaking, we all know if there is a limited slip clutch pack, the oil needs a friction modifier additive. Not much to debate there.

For the most part, the 75W synthetic base oil is pretty well accepted by most axle manufacturers. It's on the upper end of load and temperature the debate is. For many decades, 90 weight (@ 100 deg C) was the universal standard. Now we have ridiculous new specs like Mopar's 85 weight for my truck. This is another one of these microscopic fuel economy measures that's miniscule. I pay no attention to that.

The 140 weight is for high temp, high load towing applications. Anything other than that, 90 weight is fine. Hypoid gears have used 90 weight for years with excellent longevity. It is the equivalent of an SAE 40 weight engine oil.

For the few of us with torsen all gear "anti-spin locking" differentials, friction modifier additive is not only not needed, it is detrimental, delaying gear lockup under slip condition by enabling spider gear spin longer with reducing bearing friction. It says so right in Eaton's Detroit Locker Manual. AAM says nothing, but the same gear type.

The only 3 gear oils I found without LS additive were the Mopar 75W-85, Mobil Delvac 1 75W-90, and Red Line 75W-90 NS

*end rant*
 

Mister Luck

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Amsoil catalog came in the mail today.

I looked this up to share


NOTE: AMSOIL synthetic gear lubes do not require this additive. However, not all differentials respond the same and the addition of AMSOIL Slip Lock will eliminate chatter in mechanically sound differentials.

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