I'm about to change my rear differential fluid while im rebuilding my transfer case, however i dont have an owners manual, so i dont know what type of fluid to use. It has the limited slip 8.25 rear, so i know i have to use that bottle of friction moddifier, however i just dont know what weight oil i should use. If anyone knows exactly what to use, could you tell me, and also what is the capacity so i know how many bottles to buy. Thanks.

 

you'll need about 3 quarts and i'd use red-line 75w-90ns in it. it already comes with the friction modifier in it. another tip for you is if your gonna do the diff fluid, either pump it out with a hand pump or motorized pump (marine shops have them). makes life easier if you dont want to yank the cover off.

welcome to df...

 

Um

Dude

75-90NS does NOT have the modifiers in it. I used to use that in my Subaru's 5-speed as most normal synthetics DO have friction modifiers, which caused the syncros to not work well enough.

75W90 NS
This GL-5-type geal oil doesn't contain the friction modifiers for limited-slip hypoid differentials. This makes the transmission synchronizers come to equal speeds more quickly, allowing faster shifting and much easier low-temperature shifting. Can also be used in racing limited-slip differentials where weak spring design causes too much wheel spin.

 

um dude, you are correct, I have it backwards, it's the 75w-90 that has it.

good catch.

 

It took me a while to find the NS stuff when I had my Impreza - I was just using M1, but it's got modifiers and I was constantly grinding gears because the syncros weren't working fast enough.

 

So the Mobile 1 is synthetic but does not have the friction modifiers in it? And you are suggesting using a synthetic and NOT adding the friction modifiers. I am understanding this correct? I too am about to change fluids in both front and rear diffs and at this point I am confused. Can you clarify? Manual says friction modifiers from Mopar but my understanding is there are some non factory synthetics that have the friction modifiers already in them. Do I or do I not want to use the aftermarket fluids with or without friction modifiers in my front and rear differentals?

Thanks

Joe

 

id use factory stuff.... cause you know it wont mess anything up... and you wont be mixing different type of fluids that can be somewhat catastrophic..... put it this way... you go to a dealer... give them your vin.. and ask for the fluid... and when you do the fluid change properly... and something crazy goes on with it.... dealer's problem now with your axle's... thats how i like to look at it... chances of them replacing your axles.... not likely... chances of the parts department giving you the wrong fluid... not likely...

 

Well thanks Steve, but im not entirely new to DF, as you have answered a few of my q's about my transfer case.......but anyway i'm still a little lost. 75-90w seems about right, so if I buy a bottle that does not contain any friction moddifiers, then i have to but that 4oz bottle and add that as well, right? I'm probally going to use Valvoline Syn-Tech 75-90W, as I've always had good luck with Valvoline petrol products. It's not as pricey as the redline, but it will do for now. This spring im redoing my ring and pinion and also new bearings as well, i just dont have the funds to do them right now as i just dished out some cash for my transfer case parts. So i figured i would just run the Valvoline product for now, and when i do the overhaul next spring i will switch over to Redline, if I don't like the Valvoline. Thanks for answering my questions, i appreciate it alot since i am in the dark and don't know what to use.

 

Mobil 1 synthetic gear oil DOES have the friction modifiers in it. Great for limited slip differentials, not great for manual trannies with syncros.

In my Ram I run 80w-140, but it gets beat on, hard.

 

I know i use mobil 1 in the rear and front diffs. I cant remember what i used for the transfer case. Id have to look in up in the manual. But i tell you one thing, when i changed the transmission fluid, it was thick. I had just change my diffs before taht and the transmission fluid smelled just like mobile 1. Turns out it was mobil 1. Some idoit at a garage had put mobil 1 GL-5 in the transmission. I put redline MT90 in and i must have gained 60 HP. Sure felt like it.