HOW TO: Change your front/rear diff oils

[lynxer]

I did my rear tonight. While I was waiting for the RTV to dry I decided to throw a new water pump on the libby. By the time I got that done I called it a night.

This was a very easy little task that can save alot of money down the road. The hardest part of the whole thing was filling the diff back up with lube. I modified my funnel a little bit and dumped the bottle in kind of infront of the gas tank and up as far as I could with a tube coming off the funnel into the hole. I know there is probably a special tool or pump, but I made it work.


Someone was asking where to put the jack stands. Here is where I put them. I dont know if it is correct or not, but seems alright to me.

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[family KJ]

Gonna do mine tomorrow for the first time.(rear) Looks like I should use the RTV, is it bad to use both the gasket and RTV as I have both or just a waste?

 

[glassbrain]

Gonna do mine tomorrow for the first time.(rear) Looks like I should use the RTV, is it bad to use both the gasket and RTV as I have both or just a waste?

I've always just used RTV with no problemo, both would be redundant.

 

[jeepskate]

So I'm confused about one thing. I see that people say to let the RTV cure for 30 mins or longer before putting the cover back on. But the factory service manual says this: "CAUTION: If cover is not installed within 3 to 5 minutes, the cover must be cleaned and new RTV applied or adhesion quality will be compromised."

Why the big difference? Is the Mopar sealant different than the RTV we buy at a parts store?

 

[jnaut]

I used a gasket and rtv (really to hold the gasket in place) and I put it on right away. I'd be reluctant to let the RTV cure for 30 minutes.

 

[kjpilot]

FWIW, O'Reiley sells a pump that fits both quart & gallon geal lube containers. it looks like a pump on a liquid soap bottle. It runs about $8, totally worth it!

 

[richar43]

So here is a question for anybody, and I have read this over, and plan on doing the diff fluid in the front and rear, I plan on using the 75w-140 in the rear, but the front states to use 80w-90 in the front, however i noticed in this thread of someone using the 75w-140 in the front as well, is this ok, or do i have to run the 80w-90?, one other question about pumping out the rear fluid, is it better to do that or just pull the cover, and inspect everything. This is something i will be doing within the next 5,000 miles, as to that is when i will be at 30k.... I have the command trac system in it with the 8.25 rear end in it, do i need the friction modifier, I can't find any info for this?

 

[yellocoyote]

I use the same weight gear oil in both front and rear diffs with no ill-effects so far (don't recall which off the top of my head, but it's written down in the jeep). I've changed both of them 3x each now since I bought the KJ in early 2007.

As far as the rear differential, I prefer to remove the cover so I can inspect for damage and clear out the magnet from any debris... and I like knowing that there's a newer seal on it (I use RTV). I wouldn't be comfortable with it having not visually assessed for any damage, etc. That's just me.

I also have CommandTrac, and do not use a friction modifier.

 

[richar43]

YC, thanks for the info, so I plan on using the same in both the f/r diffs, and I will pull the cover just to check things out, what are your thoughts about the lubelocker gasket?, I plan on using one of these as well...

 

[HoosierJeeper]

So here is a question for anybody, and I have read this over, and plan on doing the diff fluid in the front and rear, I plan on using the 75w-140 in the rear, but the front states to use 80w-90 in the front, however i noticed in this thread of someone using the 75w-140 in the front as well, is this ok, or do i have to run the 80w-90?, one other question about pumping out the rear fluid, is it better to do that or just pull the cover, and inspect everything. This is something i will be doing within the next 5,000 miles, as to that is when i will be at 30k.... I have the command trac system in it with the 8.25 rear end in it, do i need the friction modifier, I can't find any info for this?

You have an 07....so no LSD rear. No friction modifier needed.

 

[yellocoyote]

YC, thanks for the info, so I plan on using the same in both the f/r diffs, and I will pull the cover just to check things out, what are your thoughts about the lubelocker gasket?, I plan on using one of these as well...

I have one of these as well, but haven't used it yet. I forgot I had it the last time I serviced the rear diff. I do plan on using it the next time. I've heard very good things about them, so I'm anxious to test it out. Probably won't happen till this fall/winter at the earliest. RTV has worked for me so far.

 

[cplchris]

is it ok to use permatex ultra black rtv?

 

[LibertyFever]

Since my Liberty's warranty has expired I've decided that it's my responsibility to perform the routine maintenance. So today I replaced the engine oil & filter, a real simple job, the old filter wasn't all that hard to reach & wasn't very hard to remove. The diff was another story.

To make filling the diff easier I tried to put jack stands under the frame in front of the rear tires so the axle would drop some but I was on a slight hill and they were leaning. So I raised the frame by lifting the rear frame with a floor jack under the hitch.

I've changed diff fluids before so this job wasn't to difficult to do but this time I was filling my diff with 85-140 weight oil (recommended for towing & offroad). The 85-140 weight oil is really thick and difficult to get into the diff so I setup an IV drip;

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Pretty clever Eh?
While I cleaned up my tools the fluid slowly dripped into the diff.

Say, do you like my cherry red diff cover? Maybe I should do the gas tank skid plate in red too.

Should I put the 85-140 weight oil in the front diff? I thought it was only recommended for the rear diff.

 

[richar43]

Tonight I changed my f/r diff fluid, using this tutorial, and it was very helpful, I ended up using a simular IV drip as well, very clever idea.... thanks....

 

[LibertyFever]

I'm having second thoughts about filling my rear diff with the 85-140 weight oil. It will likely get pretty stiff come February. Maybe like taffy :gr_grin:

 

[offrovering]

do 75w90 or 75w140.

use a garden sprayer from big box store, cut the tip off and use that as your filler.

 

[boebr1]

you can buy a hand pump at the parts store. one end screws onto your bottle, the other end has a clasp on it that will hold it in the fill hole until you squeeze it to release. hook up your bottle, put the tip in the hole, and pump away... you'll get her filled up with minimal effort, and you can do it from underneath... wait... i'm still talking about gear lube right?

 

[LibertyTC]

Ya well I use the largest Vet Syringe 6 oz and guaranteed to scare the hell out of someone if you want to.
This works great for removing /filling oil and you can measure, before an injection!:jawdrop:
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[trazman]

I have to change the diff fluids to, but I can't find 75w140 fluid, would it be something wrong if I put in 75w90 or no? I drive a lot off road...

 

[TwoBobsKJ]

I have to change the diff fluids to, but I can't find 75w140 fluid, would it be something wrong if I put in 75w90 or no? I drive a lot off road...

Use standard 85-140 gear or dino oil. Yes, it is a bit thicker than the synthetic 75-140 but it is MUCH cheaper and actually better for the differentials anyway.

Check out this thread for details on the gear/dino oil for confirmation.

Bob