Changing Differential Fluid

[TerryMason]

One important maintenance item that is often overlooked by owners is changing the fluid in your trucks differentials. The fluid in your Jeep's front and rear differentials will need to be changed at regular intervals (for my 2005 it's every 12000 miles), and should be changed after a water crossing.

So what's a differential? In your four wheel drive Jeep there are two differentials (often called a diff or pumpkin). The differential's job is to take power from your drive shaft and transmit it via the axles to your wheels. It does this using a series of gears. As the power is transmitted, heat is produced, and gear oil is used to cool the heat, and to lubricate the gears (similar to what engine oil does in your engine). It's this fluid that breaks down and needs to be changed.

Luckily, changing your diff fluid is reality easy. Let's start by identifying the parts you'll be working with. This is a standard rear axle - while yours may be different, the fluid change is roughly the same.

1. We'll begin by positioning our oil pan under the rear differential (to catch the gear lube that will come pouring out). Then unbolt the bolts holding the diff cover on.
   
   
   
   
   
2. Once the diff cover is unbolted you may need to pull on it with your hands, or even use a screwdriver to break the seal (it's most likely held on with RTV at this point), but be very careful not to gouge the metal of your cover, or the axle housing. Once the cover is off, and most of the fluid has drained into your oil pan, you'll need to clean things up a bit. I prefer to use a paper towel and soak up any extra fluid. You'll then need to clean off any remaining gasket material so that your axle housing is nice and clean.
   
   
   
   
   
3. You'll want your diff cover to be just as clean as the axle housing. Just take your time and clean everything thoroughly.
   
   
   
   
   
4. Since my cover was pretty rusted I took the time to shoot it with some spray paint.
   
   
   
   
   
5. You'll need to put down a bead of RTV now. This is most likely the hardest part of the process. put on an even amount that won't leave any gaps.
   
   
   
   
   
6. Before the RTV dries you'll want to attach the cover to the axle housing. I find it easiest to hold the cover very lightly against the axle housing and begin to insert the bolts until they are finger tight, then do the next bolt. When you go back and torque the bolts to 30 ft. lbs. tightened in a criss-cross pattern.
   
   
   
   
   
7. Now refill the differential with fluid and you're good for another 12,000 miles.

[Jeepergeo]

The paint on the cover looks great. You should consider touching up those bolts too (they are not screws).

[TerryMason]

The paint on the cover looks great. You should consider touching up those bolts too (they are not screws).

oops - I've updated the post.

Yeah, the painted cover just makes the whole axle look bad. I think that I just need to paint the whole thing.

[larrymo49]

FYI...That little rubber fill plug found on many Dana 35's may also need to be replaced if it is not sealing properly. That part cost me $8.00 at the Jeep dealer.

Nice write-up, Terry!

[rush2112]

Can someone tell me what RTV is, the article is great, plain and easy to understand. It comes at a good time, I'm told my rear has a small leak. THANX again for the post

[Jester32]

Rtv is basically silicone sealant.

[TerryMason]

Can someone tell me what RTV is, the article is great, plain and easy to understand. It comes at a good time, I'm told my rear has a small leak. THANX again for the post

As Jester said, RTV is like silicone or perhaps caulk. I used Permatex Ultra Black on this job.

If you bolted the metal diff cover directly to your axle, there would be plenty of leaks around it, where the metal didn't mate perfectly. You can prevent these leaks by either using a gasket (purchased at any auto parts store), or some RTV. They both achieve the same result, and I get the impression that choosing one way over the other is just a matter of personal preference.

It's probably easier to install a gasket, since you just line up the holes and bolt it up, where with RTV you'll want to carefully push the cover into place so that you don't end up smearing the RTV everywhere. On the other hand, RTV is probably cheaper, and one tube is generally enough to do a variety of jobs.

[rush2112]

Thank you both, I think I'll try the RTV...Now to figure out what type of fluid goes in, any suggestions?

[SteelHeadz]

Try to find a specific RTV called Axle RTV. It's les likely to leak and as far as fluid is concerned, i use synthetic 75/140 on my front and rear axles. For light duty works, 75/90 will do.

[TrailRatedRN]

To RTV or not to RTV? lol. I have a LubeLocker gasket n the rear 5,000 miles - leak free. I have a regular gasket in the front - garage is clean, but I do believe I c some gear oil around the edges. Never used RTV. Don't wanna scrape it off. lol

Question for u, I go at least axle deep in water almost every time I offroad. I've changed my gear oil 2 times in the LJ's 40,000 mile life. Manual says to do it at 36,000. I like to play in the creek. You reccomend I redo my gear oil w/ every run through the creek?

[808CJ7]

I recommend checking the oil in your axle after a water crossing. At least pull the fill plug and dip your finger in there to see if it's got water. Could be very costly if you don't.

[SteelHeadz]

If you like playing in the water i would suggest that you keep in mind the location of the vent tube for the axles on where they are located and if they are vulnerable from submersing or heavy splash. If they are, i would recommend that you extend the tubes farther up on the engine compartment by either replacing the hose or using a vacuum line splice to connect a longer hose for the front and rear axles. Even with this extra precaution, the water will still be able to enter the seals in the axle tubes depending on how long and how hard the axles are turning while submerged. With this in mind, as suggested by 808CJ7, pull the differential fill plug and check the condition of the fluid with your finger and see if it's milky in color. If it is, water contamination is evident and servicing the differential is highly recommended.

To RTV or not to RTV? lol. I have a LubeLocker gasket n the rear 5,000 miles - leak free. I have a regular gasket in the front - garage is clean, but I do believe I c some gear oil around the edges. Never used RTV. Don't wanna scrape it off. lol

Question for u, I go at least axle deep in water almost every time I offroad. I've changed my gear oil 2 times in the LJ's 40,000 mile life. Manual says to do it at 36,000. I like to play in the creek. You reccomend I redo my gear oil w/ every run through the creek?

[69jeepcj]

Steelheadz is absolutely correct. Your gears are hot from turning all the time and when you enter water, it is a instant cool down which creates a vacume and CAN suck water in from the vent tube.
The vent tubes should have a little valve on it, It is subposed to be a check valve that lets built up presure out but not anything in. They usually don't work and when you cross water, water gets sucked in through the tube. I doubt you have a hose on the axle, you probably just have a nipple on the axle tube with a little round valve on it. looks kinda like a large valve stem cap for your tires. you can take that cap off and put a hose on your axle and run it to a high spot so water cant enter it. Your transmission and t-case will probably have one as well and you may want to do the same with them. I ran my front axle tube up into the engine compartment as steelhead suggested and ran the rear axle up as high as I could get it in the rear wheel well. I drilled a hole in the rear wheel well of my last jeep and ran the hose up into the interior compartment on top of the wheel well, (not a good idea, smelled like gear oil inside the jeep all the time). It must be too early... I cant remember for the life of me how to spell vacume, lol. Need more coffee.

[69jeepcj]

As for changing your fluid EVERY TIME you cross deep water, I dont do it. If my seals seem to be keeping water out I just keep an eye on it, because it can get expensive changing oil eveytime I go wheeling. If I see water has entered I will fix the problem so im not changing oil everytime.

[Ghost Rider]

I also had issues with the rubber plug not sealing properly so I had another cover and welded a bong to it that has 5/8 threads on it so I can use a regular threaded plug with copper washer on it. Leaking problem solved.

[chicagobrownblue]

So Midas pointed out that I had missed my 15,000 mile axle fluid change. Because they need to tear off a plate or two, it was going to cost $500. I took my Jeep Liberty 2007 to my regular mechanic. When he read "drain and replace axle fluid" on the order he said "This ****es me off. This is not needed. If you had 110,000 miles yes, but not at 19,000 miles. The synthetic oils they use can last over 100,000 miles." I said, but the Jeep owner manual recommends it. He said "It is not needed." Then I asked him if the plate(s) need to come off to drain the fluid properly. He said "Yes, but then it might leak." He checked the level on both axles which was fine. This is all I remember my 1992 Jeep Cherokee required.

At least Midas was correct that I needed brake work. But Midas does not even have to say, "We recommend the axle fluid..." Jeep does it for them.

[TerryMason]

He said "It is not needed." Then I asked him if the plate(s) need to come off to drain the fluid properly. He said "Yes, but then it might leak."

Changing the fluid in your axles is more about how you use the vehicle than anything else. If you're driving through water, where it could have possibly gotten into the axle, then you should drain and replace the fluid. If you just drive around town then I tend to agree with your mechanic.

He's correct that if you remove the cover then the axles may leak - when I bought my Jeep the front was leaking slightly from the poor job the previous guy did. If the mechanic takes his time and does a good job then there won't be a problem.

[Dragon5126]

Route it up to the inside of your fuel filler housing... simple access to mount it on the interior of the tub without going to the passenger compartment.

[Dragon5126]

Almost all covers should be replaced with an RTV sealant even if a gasket is used... Per virtually every repair manual, to prevent leakage. In the real world the diff covers are too easy to bang and cause leaks on even with ductile iron covers. Ive seen a front axle hit a log, causing the cover to shift just enough to break the seal. within a few thousand miles of pure highway driving after, the dreaded drips started. It's not a big deal, just a PITA. but it's cheap insurance any time you work in the diff. RTV it and make sure you get all the bolt holes.

[offthebeatenpath]

Great write-up, There's one more thing you can do to make it even easier. I use replaceable gaskets by Lube Locker. They work great and you dont have to use RTV. So no scraping it off. As I said there reusable. One guy I know has used it over 10 times now. They're great. They cost about $27.00 and are well worth it. Just thought this might help.