What grade gear oil are you running in your Rubicon?

[g2020]

I did Amsoil 75-140 in the rear and Amsoil 75-90 in font.
4.56's and 39's. I don't tow at all.

I know what I wrote (75W-140 for both axles), but the combination of viscosity grades that you installed is pretty much what I would do (75W-85 in front, and 75W-140 in the rear diff). It was just simpler to recommend 75W-140 for both axles.

Before I mention aftermarket brands, it is important to note that MOPAR synthetic gear & axle lubricant, installed by a dealer, is always an exact match and comes with a 24-month parts & labor warranty. As stated in the owner's manual, the mileage service interval for severe duty is 40K miles (with an inspection at 20K miles). For DIY, the MOPAR warranty is implied-only (limited to product-replacement).
Reminder: When using MOPAR for Trac-Lok limited-slip (LS) rear differential, friction modifier must be added separately.

I have never used AMSOIL Severe Gear 100% synthetic gear lube. However, I know that their warranty covers damage to other parts and their gear oil has a supplemental guarantee of 50K miles for severe service. This is 25% higher than the OEM severe service mileage interval. Also, they use squeeze-bag packaging for easy installation.

A strong competitor is Valvoline full synthetic gear oil. Their compliance documentation could be better, but their warranty also covers damage to other parts, they also use squeeze-bag packaging (easy installation), their gear oil is available everywhere, and the price is right.

RED LINE full synthetic gear oil should also be mentioned because they are the only other brand, besides AMSOIL, that offers 75W-85 (an exact match to the OEM grade). Just like AMSOIL Severe Gear, compliance with each material standard is stated in writing (including MS.10111 for friction modifier). The only drawback is that their warranty appears to be implied-only (product-replacement or money-back). This might be unimportant to loyal RED LINE customers, but the fact remains that at least three of their aftermarket competitors back their products with a warranty that covers damage to other parts.

If you want a warranty to stick, do the job (or have it done) right. Keep receipts & invoices and take photos. If you don't know what you should be looking for or what to clean after removing each differential cover, ask someone who is qualified or have the job done at a shop.

Opinion

• MOPAR synthetic gear & axle lubricant is best for someone who prefers to use only OEM parts, regardless of the DIY warranty implications
• AMSOIL Severe Gear 100% synthetic gear lube is best for someone who is confident in the 25% longer mileage service interval and wants to save time
• Valvoline full synthetic gear oil is best for someone who is confident in the OEM service interval and wants to save money

To check all of the details, see Section 1.3 of my post on Links to Prices.

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[cb4017]

Amsoil Severe Gear 75W-140 is one of the best. I've used it in my JKU and my 21 JT. My 25 Mojave will get it eventually when I service the axles. Sure wish JTs still had the differential drain plugs.

Friction modifier is not needed with a Rubicon locker.

 

[JTGuy]

With my 4.88s I use Torco 85-140 RGO GL-6 non synthetic. I believe it's what Currie uses so that's good enough for me.

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