Differential Fluid Type

[JeeplifiedLaughs]

Hello,

Apologies in advance if this is the incorrect forum for this post.

I’ve been reading through several posts and I‘ve narrowed down my answer but I’ve never changed the differential fluid on my Jeep so I’m kind of scared of messing it up even it seems simple enough.

Based on the info I’ve found on the forum threads, it seems like I should probably stick with either SAE 75W-90 OR SAE 75W-140. The most referenced brands are Royal Purple or Valvoline so I guess I’ll go with the later.

My question is, since I primarily use my Jeep to drive to and from work everyday, I don’t do any towing or off-roading (sadly I don’t have time but would like to in the future), and the only water my Jeep goes over is the occasional rain puddle, which dif fluid would meet my driving needs?

For reference, here are some of the specs:

2018 Jeep Wrangler Sport Unlimited JL

DANA M186 FRONT AXLE

3.45 OVERALL TOP GEAR RATIO

DANA M200 REAR AXLE

CONVENTIONAL DIFFERENTIAL FRT AXLE

CONVENTIONAL DIFFERENTIAL REAR AXLE

Although the manual recommends the Mopar Gear & Axle Lubricant (SAE 75W85) (API GL-5) for both the front and rear with a modifier additive needed for models equipped with Trac-Lok Limited Slip Differential, the general consensus is to stay away from Mopar (or at least its not the best option) and that the additive is not really needed.

I took also took a look at the Rebuild Specifications sheet for the DANA axles and it seems I have the DANA 30 for my front axle and DANA 35 for the rear. The recommended lubricant is the SAE 75W-140 for both but I saw someone mention that that type of lubricant was more for those that did off-roading and went over water constantly, which mine really doesn’t.

So, should I just use the SAE 75W-90 for both axles, or should I use a combination of the 90 for the front and 140 for the rear, or just go for the 140 for both? I average around 400 miles per week in driving, so I’d like for whatever option I go for to not affect my gas mileage too significan’t if at all.

Also, it doesn’t seem like my Jeep has the Trac-Lok Limited Slip thing as I don’t see it on my build list but I maybe wrong— but I’m not also not sure if that makes much of a difference.

Any advice is greatly appreciated! Thanks!

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[jadmt]

I have had good luck with Mopar gear oil. used it on my last 4 JK's and my power wagon.

 

[azwjowner]

So, should I just use the SAE 75W-90 for both axles, or should I use a combination of the 90 for the front and 140 for the rear, or just go for the 140 for both? I average around 400 miles per week in driving, so I’d like for whatever option I go for to not affect my gas mileage too significan’t if at all.

The very simple answer is 75W-140 is better protection, but 75W-90 is adequate, and 75W-140 will result in 1% less gas mileage (there is a published study on exactly this subject; I've read it before). You can do the math on 1% - that's $20 on $2000 per year.

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