HELP!!! JK Rubicon Diff Fluid Quesions...
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JK Newbie
Joined: Feb 2007
Posts: 86
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From: North Fayette Twp, PA
HELP!!! JK Rubicon Diff Fluid Quesions...
Ok, so a friend of mine is on her way over with her 07 Rubicon. We are putting RockCrusher Diff Guards on her Jeep and filling the diffs with Royal Purple fluid. So, I have a question...
The JKs manual calls for 80w-90 in the front axle, but 75w-140 in the rear. Does this seem right? I run 75w-140 in the front and the rear of my 04 TJ Rubicon. Should we run the 80w-90, or stick with the 75w-140 in both?
The JKs manual calls for 80w-90 in the front axle, but 75w-140 in the rear. Does this seem right? I run 75w-140 in the front and the rear of my 04 TJ Rubicon. Should we run the 80w-90, or stick with the 75w-140 in both?
JK Newbie
Joined: Dec 2006
Posts: 87
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From: Allentown, PA
The Service Manual says:
Axle Differential (Front)
Mopar® Gear & Axle Lubricant (SAE 80W-90) (API GL-5) or equivalent.
Axle Differential (Rear)
198 RBI (Model 35) and 226 RBI (Model 44) - Mopar® Gear & Axle Lubricant (SAE 80W-90) (API GL-5) or equivalent. For trailer towing, use Mopar® Synthetic Gear & Axle Lubricant (SAE 75W-140) or equivalent. Models equipped with Trac-Lok require an additive.
Axle Differential (Front)
Mopar® Gear & Axle Lubricant (SAE 80W-90) (API GL-5) or equivalent.
Axle Differential (Rear)
198 RBI (Model 35) and 226 RBI (Model 44) - Mopar® Gear & Axle Lubricant (SAE 80W-90) (API GL-5) or equivalent. For trailer towing, use Mopar® Synthetic Gear & Axle Lubricant (SAE 75W-140) or equivalent. Models equipped with Trac-Lok require an additive.
JK Newbie
Joined: Apr 2007
Posts: 99
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From: Birmingham, Al
You do not need to use the additive with the Royal Purple. The necessary friction modifiers are already present in their gear oil. The 75-90 or the 75-140 will work fine in the diffs. The 75-140 is to be used if the diff will be under a heavy load from towing and possibly heavy offroading. I currently run the 75-90 in both of my diffs and have had no problems at all.
If you want to verify this please call the tech support line for them. They are very helpful and can further explain this. I believe the first number (75 or 80) has more to do with the climate temperature that anything. Good luck.
If you want to verify this please call the tech support line for them. They are very helpful and can further explain this. I believe the first number (75 or 80) has more to do with the climate temperature that anything. Good luck.
Last edited by Shoal Creek; Jun 16, 2007 at 07:41 PM.
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JK Enthusiast
Joined: Apr 2007
Posts: 147
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From: Edmonton, Alberta
So wouldn't running 37's on a daily driver be considered "heavy load" as compared to stock? If so, should 75-140 be used front and rear?
JK Newbie
Joined: May 2007
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From: Germany
first #: viscosity class cold (@ 20 ° Celsius)
scnd #: viscosity class warm (@ 100 ° Celsius)
=> a 140-er gives you much more reserves at high temperatures, which occurs with heavy load or high speeds for long time. You won´t need it in the front axle.
My oponion regarding the rear axle: If a manfacturer makes a difference between heavy load or not, doesn´t that mean the construction is a little "at the limit"? Never heard of that at other brands/ models. Would take the 140-er in every case here ...
scnd #: viscosity class warm (@ 100 ° Celsius)
=> a 140-er gives you much more reserves at high temperatures, which occurs with heavy load or high speeds for long time. You won´t need it in the front axle.
My oponion regarding the rear axle: If a manfacturer makes a difference between heavy load or not, doesn´t that mean the construction is a little "at the limit"? Never heard of that at other brands/ models. Would take the 140-er in every case here ...