Rubi Rear diff fluid

Rebel JK

Rebel JK

New member
Im changing my rear oil out later today and am planning on going with 75-140 synthetic, as I will be towing a small trailer up to the Sierras. Question- Does anyone have any prefered brand(s)? I was leaning towards Purple or maybe Redline, because thats what the local parts store will probably carry.

With these, will I need to add the 4.0 oz of limited slip additive recommended in the book? I read that some of the synthetics already have the additive. Im running the stock D 44 with 5.38 gears on my 08. Thanks guys.
 
Friction modifier is only needed with limited slip differentials. With a locker, it isn't needed and, even if it were, synthetic gear oil typically has it in it. Having said all that, gear oil is pretty much gear oil and you really can't go wrong with whatever you choose to get. I change mine out often enough that I've started to use old dino again. Depending on who you talk to, it's the better way to go anyway.
 
Thanks Eddie. Will probably go with the synthetic just to be on the safe side with a little towing (1 trip) in mind. I'm at 50k miles now and not pulling the cover this go round unless I see anything on the plug.
 
Cannot hurt to use synthetic since it appears you do not change it often, so cost is not a major factor. And like Eddie says, most have the additive already. I switched all my fluids over to Royal Purple in my 2011. My friends that race swear by it through dyno proven horsepower gains (at least for the motor oil). Every little bit helps with the 3.8L!
 
Black Ops said:
Cannot hurt to use synthetic since it appears you do not change it often, so cost is not a major factor. And like Eddie says, most have the additive already. I switched all my fluids over to Royal Purple in my 2011. My friends that race swear by it through dyno proven horsepower gains (at least for the motor oil). Every little bit helps with the 3.8L!
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Depending on who you talk to, synth lube will not dissipate heat as well as dino lube. But, I'm not gear/axle expert so, I couldn't say if this is true or not and because of it, it is still what I would recommend especially if you're running a LSD. I have long stopped running Royal Purple though due to its excessive cost.
 
wayoflife said:
Depending on who you talk to, synth lube will not dissipate heat as well as dino lube. But, I'm not gear/axle expert so, I couldn't say if this is true or not and because of it, it is still what I would recommend especially if you're running a LSD. I have long stopped running Royal Purple though due to its excessive cost.
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I was told the same thing by an old school mechanic and long time offroader.. He won't put synthetic near his differentials.

Sent from my SGH-I747M using WAYALIFE mobile app
 
Don't want to start a flamefest or anything like that, just figured to add some info. Heat in fluid is generally created by the fluid itself. Synthetic fluid does a better job of lubricating, thus reducing heat (aka friction.) Synthetic oils also more capable of withstanding heat, which in turn, keeps them lubricating better, which in turn, keeps the temps down. Plenty of Harley guys report lower engine temps from running synthetic oil. The best dino fluid is never better than synthetic, in any measurable category. If you wheel a lot, and change your fluid all the time, you may not even notice the difference, but it would be incorrect to say that dino is superior in anything. Stay away from RP. Buy Mobil1 if it's on sale. If you want the best, buy Amsoil or Lubrication Engineers.

If you are bored at work, and want a little reading,


http://books.google.com/books?id=J_...onepage&q=specific heat of lubricants&f=false
 
Hmmph, when running RP after a 40m road trip my rear diff was 165 degrees. Same trip with Lucas Dino was running 145-150 degrees. My Detroit locker banged and clanked all the time with RP. It only pops every once in awhile with Dino. At least for me Dino works better.
 
mkjeep said:
Hmmph, when running RP after a 40m road trip my rear diff was 165 degrees. Same trip with Lucas Dino was running 145-150 degrees. My Detroit locker banged and clanked all the time with RP. It only pops every once in awhile with Dino. At least for me Dino works better.
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RP is probably some of the worst lubricants on the market. Try running a quality synthetic and report back. Also, keep in mind that Royal Purple is NOT a 100% synthetic lubricant like say Amsoil. It is a dino oil with synthetic additives.
 
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