Ye Ol' Cherokee

98 Cherokee 4.0 Sport 4x4 (part time) with about 150,000. The carfax says the differential fluid was changed at 40,000k at the dealer. It now has at least 150,000k, and has never been changed. This jeep is a DD, and has never been a trail-jeep. It is 100% stock with NO lift.

Before this jeep, I have been a car guy, and have not even given a "differential" a second of my thought. So, now i'm thinking about it...

I am assuming this is well overdue to be done, but how serious is it that its been at least 100,000k miles since it has last been done? I REALLY don't want to change the fluid, just to find out I caused a problem.

Anyway, I am really reluctant to dive into this because I have ZERO knowledge of this type of maintenance. I have no access to a shop, and limited tools, so is this something I could do with the proper guidance? I checked out some write ups, but I feel like i will be biting off more than I can chew with this.

Is the cover hard to take off? Is there anything specific to be careful for? What is the process? RTV or Gasket?

Or should I just save myself the trouble and have it done at a shop? I don't mind, if its not too expensive... (Est. Cost?)

Demonoid369

Semi short answer: There is this magical thing called google and YouTube, great things to use to learn about this.

Real short answer: yes, change it.

Demonoid369

Just actually read this part. Are you the son of bimmerjeep or at least related to him?

Ye Ol' Cherokee

I've interacted with him on the forums, but no, no relation... why do you ask ? lol

CrawdadSlim

Pump the old fluid out if you feel you can't tackle the job.

sycoglitch

Just Google a video please OP. Pumping it out won't let you see if there is any damage to gears.

Ianf406

It's really really really easy. Just pull the bolts ( there are not many) drain the fluid, clean the old gasket off, put a new lube locker gasket on or use black RTV, bolt the cover back on, put some 75-90 in it until it overflows from the fill hole. Replace fill bolt and you are done. It is as easy as changing a tire. You'll be fine! "Hardest" part is getting the holes to line up when reinstalling the cover.. Still really easy.

salad

Repeat after me:

Not changing fluid for fear of causing problems is like not changing your underwear after you **** yourself because you're afraid that clean clothes might chafe.

Sounds kinda ridiculous, doesn't it?

1. Remove all diff cover bolts but the top one. Just loosen that.
2. Chances are the diff cover was sealed with RTV instead of a gasket. Use a box cutter to cut into the RTV around the perimeter of it.
3. You'll probably need a hammer (mallet or hammer + wood block) to break the diff cover loose
4. Hope you have a drain pan underneath it! Good idea to keep your lips closed...
5. Once the gush has stopped, remove the final bolt at the top and take the diff cover off
6. Inspect the guts and the oil that came out for damage. You're looking for chipped teeth and excessive metal shavings.
7. Yes it smells ****ing awful. Don't breathe too much of it
8. Using a wire brush on a Dremel, drill, or angle grinder, clean all the RTV and rust off of the mounting surface on the differential. Pop out the rubber plug and do the same to the cover.
(Optionally, you can clean the outside of the cover and paint it too)
9. Clean the inside of the differential and the cover with non-chlorinated brake cleaner. I prefer hexane or heptane type.
10. Go get some fresh air while that mess dries, get the oil pan out of the way
11-13. Refer to instructions on your RTV for how to form the new seal, assemble the cover, and let it dry if necessary. I recommend Permatex Ultra Black or The Right Stuff (which is grey)
14. Fill to the bottom of the fill hole with 75w90 API GL-5 gear oil. If you have a limited slip differential you'll need to add a friction modifier (already present in most synthetics)
15. Check for leaks and put the plug back

Should be about it. There are probably writeups with pictures and videos if you want. Google is the master.

Demonoid369

Lmfao hahaha I'm literally laugh out loud haha

Ye Ol' Cherokee

Salad, you hit me with this quote when I first joined, when I was asking about tranny fluid change lol.

I only asked because i am a complete newbie with differentials.

Awesome quote though lol

Ye Ol' Cherokee

I think this is my biggest concern which is holding me back. Anybody can drain and fill something, but i am always nervous with doing things like spraying something somewhere, that you can't leave in there...

Do i just spray it all over in there, and leave it to dry? or do I have to wipe it out? Do i have to get every drop out? Every post i read is like "OMG you cant leave .00001 ounces of the brake fluid in there!!!"

Whats your take?

jake7

It pretty much dries on its own. Buuuut spray in tehre to clean it all out and wipe off the excess. The rest will air dry while you're cleaning the cover.

Whiplash

if the diff isn't filled with metal dust etc and the gears all look good you can just leave the residual hypoid where it sits. biggie is to just make sure the puddle sitting in the bottom of the case is gone (wipe with rags) and there's no dripping leaking out where the new seal will be (rtv). any oil type material left on the case to cover surface and you're gonna get a leak.

me, i'd use the brake cleaner, let it evaporate as much as possible, wipe out the inside of the case and close 'er up. solvent would work as well, but now you're into carcinogens so.....

salad

Oh did I? LOL

The brake cleaner is used to thin and push the old gear oil out. Heptane and hexane evaporate very very quickly, it'll dry on its own in a few minutes at sane temperature (it's about freezing here right now...).

To give you some context, the designed use is to wash off thick oil that brake rotors are packed in.

Ye Ol' Cherokee

See for yourself lol

https://www.cherokeeforum.com/f2/bur...o-i-do-178065/