Changing Front & Rear Differential fluids

[Bobbyfanman17]

I'm a tad confused about timeframes for changing the diff. fluid on my JT and which oil to use. It seems the owner's manual doesn't even recommend changing the diff. fluids at all. I know that's not the best maintenance advice though. I have a '21 JT, Sport S, Dana 44's, 3.73 axle, 8 speed auto, 850 RE transmission WITH the Trac Lok Anti Spin rear diff. I have 34K miles on it. No off roading, just regular highway and suburban driving, 1/2 & 1/2. Based on what I am reading in the owner's manual, I should use Mopar Gear & Axle Lubricant SAE 75W85 for the front. The back diff. should use the same too because I have the Trac Lok Anti Spin rear diff, correct or is it because I have the 850 RE transmission? I DO NOT use the 75W140 on the back differential, correct? And I should change it every 30K-60K miles? Thanks to all.

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[DiehardTory]

The maintenance schedule shows check fluid at 30000 mi on my 21. If I am inspecting, I am replacing. Replacing with the correct GL5 as called for cannot hurt or harm it is the expense factor; btw the transmission has no affect on differential fluid. On the 13 Wrangler, 140W is noted when trailer towning. I use the MOPAR Gear Lube called for in the book.

 

[kevman65]

Just make sure you use the exact spec called for.

Some additives are NOT good.

 

[JTGuy]

GL5 is good but GL6 is better. So I use Torco RGL 85-140 a GL6 gear oil, So do some Diff builders.

 

[Bobbyfanman17]

Thanks all.

 

[kevman65]

For future reference, a couple of pickle forks wedged in and ring the C top and bottom.

The pickle forks give a downward force while you ring the tuning fork.

 

[Rusty PW]

For future reference, a couple of pickle forks wedged in and ring the C top and bottom.

The pickle forks give a downward force while you ring the tuning fork.

Wrong thread?

 

[sunrise089]

Simple question so I figured I’d bump this rather than start a new thread.

I tow a lot so I plan to replace with 140 weight fluid on the rear. Since I’m already doing that what would the pros and cons be to running the same fluid in the front instead of 90 weight? If it matters I only go into 4WD a handful of times each year.

 

[DylanM]

@sunrise089
I could see there being a bit more parasitic drag due to the thicker gear oil, but I doubt it would have any detrimental effect. Only pro I can think of is you wouldn't need to buy two different specs of gear lube.

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