Need to change diff fluid

[j.o.y.ride]

I have actually never done diff fluid change on any vehicle. I assume basics are same as oil... remove lower drain plug, replace plug, fill.

2 questions are... should it be warmed from driving like oil to help it flow better? And how do you know when you've filled it properly?

Any JL/T tutorials?

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[ShadowsPapa]

Having done a few dozen - rebuilds as well as simple service, I prefer if they are warmed up.
I then let them sit a bit to allow fluid to run back out of the axle tubes if there's any appreciable amount up in them.
I always remove the cover and use a home made scraper (using a piece cut from an old milk jug) and scrape out the remaining fluid. I like to clean the housing out in case something has settled in there - like metal that doesn't run out the drain. I've found small bits from bearings before - in an otherwise quiet differential.
I never simply pull the drain plug, let it drain, then refill it. It's a great time to inspect the faces of the teeth, get a feel for the health of the thing.

Fill until level with the bottom of the fill hole with vehicle sitting flat and level. That's been a general rule for decades, as well as the spec Jeep mentions, if I recall correctly.

I have found hidden damage by pulling the cover and even though it's a bit more mess, a bit more time, it may be worth it. You don't know unless you pull the cover. Not everything happily runs to the drain hole and shows itself.

 

[$1.98]

Also loosen the fill plug before you drain.

 

[ShadowsPapa]

Also loosen the fill plug before you drain.

Heck, take it out. Let's air in so it drains faster. No reason to not take it out since it's gotta come out anyway.

 

[Jaxmax]

I agree pull the cover look around get all the debris off the magnet , be careful with the rubber gasket it is reusable, I have not done a differential oil change since 1976 on a Jeep CJ-2A, it's still the same deal. I pulled mine rear was "dirtier" then front and then replaced with cast iron covers same gasket. If you want to use factory oil your dealer will know which oil by your serial number and options....Jack

 

[whysoserious]

My rule is always loosen the fill plug first (diff, tranny, xfer case, etc.). If for some reason it doesn't come loose or you strip the plug, it makes it difficult to refill later on.

 

[JTDay]

Do it with your vehicle level meaning the frame parallel to the ground. I just used pieces of wood and measured. Super easy. The Valvoline bags are helpful to get in tight spaces and you can reuse them.

 

[LouisvEarlleJT]

Only thing I'll add is that be prepared. . .it stinks (literally). At least all the old axles I got to work on did. Maybe modern stuff is less potent.

If you mess up the reusable gasket you can just make your own with RTV.

 

[ShadowsPapa]

Do it with your vehicle level meaning the frame parallel to the ground. I just used pieces of wood and measured. Super easy. The Valvoline bags are helpful to get in tight spaces and you can reuse them.

Yes. Better for draining - and a must for refilling as "fill to bottom of hole" means with it level bow to stern, port to starboard.

I have soft bottles with tubes, also have a gun I fill from a bulk bucket for some things I do often enough.

 

[ShadowsPapa]

Only thing I'll add is that be prepared. . .it stinks (literally). At least all the old axles I got to work on did. Maybe modern stuff is less potent.

If you mess up the reusable gasket you can just make your own with RTV.

That's how you know it's the right stuff LOL. I guess I got so used to it over years, I pay little attention to the smell - other than the original lube AMC came out with for Jeeps with sticks in the mid-80s. That smelled like fish and even earned the nickname fish oil or something like that.

But it's true, the older the axles are, the longer they've sat, the more smell there is.

 

[jac04]

Any JL/T tutorials?

There are a few JL diff oil change videos out there. A quick google search will find them.

From your Owners Manual:

 

[jac04]

That smelled like fish and even earned the nickname fish oil or something like that.

Fun fact: Old diff lube (at least the "special" GM stuff) was actually made with whale oil.

 

[ShadowsPapa]

Fun fact: Old diff lube (at least the "special" GM stuff) was actually made with whale oil.

And we know what rancid or bad animal oils smell like.
There were axles where if the axle seal and/or bearing was bad, you had to pull the cover to remove the spider gear shaft out so you could push the axles in and remove a C-clip. That meant draining the differential housing just to replace an axle seal or bearing. It was a very different smell to the hypoid lube back then.
Yeah, the smells of the good old days.

 

[Rusty PW]

Having done a few dozen - rebuilds as well as simple service, I prefer if they are warmed up.
I then let them sit a bit to allow fluid to run back out of the axle tubes if there's any appreciable amount up in them.
I always remove the cover and use a home made scraper (using a piece cut from an old milk jug) and scrape out the remaining fluid. I like to clean the housing out in case something has settled in there - like metal that doesn't run out the drain. I've found small bits from bearings before - in an otherwise quiet differential.
I never simply pull the drain plug, let it drain, then refill it. It's a great time to inspect the faces of the teeth, get a feel for the health of the thing.

Fill until level with the bottom of the fill hole with vehicle sitting flat and level. That's been a general rule for decades, as well as the spec Jeep mentions, if I recall correctly.

I have found hidden damage by pulling the cover and even though it's a bit more mess, a bit more time, it may be worth it. You don't know unless you pull the cover. Not everything happily runs to the drain hole and shows itself.

I'll add on to this. Use a lint free rag and wipe down the inside of the diff cover, and inside of the diff housing that you can reach.

 

[Kirk*Mojave]

I serviced my rear diff around 3k was surprised on how little was in there. Thankfully the gasket is reusable

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