GreytSilly

Okay, give me the dummy of the day award. I couldn't stand it so I went back out and climbed under the Jeep. After quite a bit of touchy feely around the bottom back side of the diffs I found the plugs. Fluids all changed out to Mobil 1. Thanks for the write up about these plugs. Sure beats taking those covers off all the time.

A'sJK

Thanks forum for the great write-up.
Just did both axles and saved 200 bucks!
Dealership wanted too much....did it myself.

nextreme

You all mention using 75W90 in synthetic yet in the manual it says use 75W140 synthetic. Any reason?

I managed to find Royal Purple in 75W140 so that is what I am going to use, both in the rear and up front. I assume it is safe to put the full synthetic in the front diff as well?

I also got a bottle of the friction modifier from the dealer. They told me to put the whole bottle in the rear axle. I don't have the lockers but I *think* I may have Trak-Loc. I gave the parts guy my VIN and he said to use the friction modifier.

jsmoriss

The owner's manual suggests 75W90 front and rear, unless you're towing, and then you should put 75W140 in the rear only. The only difference between 75W90 and 75W140 is the 140 costs more and will provide better protection at higher temps (doesn't become as thin as the 90). You can put 75W140 in both diffs, if you like (I did). It's probably a good idea for the guys spending whole days in 4HI in sand dunes, for example...

js.

nextreme

Well I will be towing close to my GVWR so I wanted to make sure that I had the right fluids in the diffs. I just didn't want to make a mistake and put the wrong stuff in the front. I may as well put the Royal Purple 75W140 Full Synthetic all around since I am getting it for $15/litre. They want $32/litre for the Mopar fluid at the dealer Prices are in CND$.

Dustoff '68

Excellent write up...when I had my 4X Doctor differential skids installed, I asked the guys to remove the diff cover and use a Lube Locker gasket instead of the silly putty like gasket material...filled with Royal Purple, and all was done....had I read this write up, I see that I could have done it myself...anyhow, thanks for the headsup.

wayoflife

If you are towing, 75W140 is what you will want. If not, it won't do any harm to have it in but it will be thick and if you have the e-locker, it might make it difficult to disengage at times. Regarding friction modifier, you DO NOT need to add any if you are using a good synthetic fluid like Royal Purple.

nextreme

No e-locker here. Will there be any negative side effects to putting the friction modifier in with the Royal Purple? I already bought it and to be honest it would not be worth my while to go out of my way to return it, it was only about $7. Plus for warranty purposes I have the receipt to show I bought it in case I ever have a problem.

Offroadme

great write up good job i only have 1000 miles but im thinking of changing my covers

SJG

I brought my new (9000 miles) Rubi in to Jiffy-Lube for a quick oil-change. They said the differential oil was really dirty front and rear, and recommended that I let them change it out. I asked how much - they came back with $240!!! What the ??? Sorry, I'll never go back. Can't trust them anymore. I brought my jeep to a shop in a small town, they did both differentials for a total of $38. Thats using 75W140 in both. I'm amazed the oil was so dirty with such few miles. I know there is a break-in period, but still pretty amazing. I have probably used 4wd no more than 50 miles since new. I can understand the rear (I have pulled my boat 10 miles about 10 times), but why is the front so dirty?