Ok so I am going to change out my front and rear diff fluid. Any advice for persons who have already dont this would be great. I looked at the front and rear to see how difficult it will be. The rear is cake, remove the cover, clean it out, reattach with RTV, pull out the plug and refill. How can I determine what size my rear end it? V8 4X4 Quad Cab 3.92 with LSD? Also should I use 75W140 or 75W90. I live in Florida and don't expect to tow, but might go offroad. Can I just use Royal Purple and not worry about the LSD additive, or should I add some just in case? With the front I will need to take off one of my skid plates so that I can drain it. Is there a plug just like the back to fill it? I see it takes 56 ounces (1.75 Quart) and the rear either 70 or 72 ounces (2.25) quart. Do I just fill them up to the plug hole? Also is brake clean ok to spray on the gears or should I use carb cleaner? Thanks.

OK, So read the manual, it states 140 for the rear.

 

I just recently did mine when I installed my Mag-Hytec cover on the rear diff.

Just drain it and let it drip out, wipe up what you can with a lint free rag and reinstall cover with some RTV that has had time to set up. ( my cover has an O-ring)

I just used the gear oil from Dodge (Castrol synthetic) that it calls for. Use the friction modifier if you have a limited slip. Also from Dodge.

Fill to just below plug, owners manual states this I believe.

Front should be just as easy to do.

So simple a caveman can do it.

 

Wow this stuff is expensive!! it will be 100 bux just to change it myself, i wonder if its just worth it to use Mobil 1 and add the LSD additive

 

Try AMSOIL, but I still use the LSD additive, I don't care what they say! Better than having to suck some out and add it later...

Oh, and the front is kinda a bitch, practice a few times getting it back in there BEFORE you put the RTV on!

LB

 

Excellent tip.

 

LB,

You were right the front was a PITA. Make sure if anyone is going to do it, to have a 1/4 drive set, 3/8 drive set, ratcheting wrenches and ALOT of patience. The rear was easy. The front first didn't want to come un-RTV'd. Finally I got it off and out. Cleaned everything up and went to do my practice runs. That took me a while just to figure out how to put it back on. I finally figured out you use the extended part of the cover and the vent tube as a guide to go around the power steering. But it's back together and I'm just going to let it dry up before I drive it

 

I've found an easier way to change the fluid. Go to Autozone and buy a cheap in-line suction pump. They look like a big tube of caulk with a T handle on the end and a flexible 1/2 tube. Stick the tube into the fill plug and angle it down to the bottom of the differential and suction the old fluid out. It will take several sucks to do so. Reverse process for re-fill. Gets at least 95% of old fluid, and you don't have to pull off the cover.

 

I may do that from now on. I had to do it the first time though. I wanted to get all the wear material out.

 

I have a question about changing out the differential fluid. I was telling my buddy that I was going to change the fluid in my differentials. He told me that I needed a impact wrench to get the bolts off. Can I do this job with the right size ratchet set. I didn't want to get into the job and round off all my bolts and or not be able to get my bolts undone. Let me know what you guys used to get do this job. Thanks for the suggestions.

 

No you do not need an impact wrench, I did mine with a ratchet and a bit of elbow grease, really wasn't an issue.

As for the 9.25 vs 8.25 question:

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