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Unread 08-04-2011, 06:51 PM   #1
wschilawskiw
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Question Royal Purple Differential - FM?

Hey all,

I have an '02 4.7 with Quadra-Trac II. I'm looking at changing the differential fluid and I'm wondering what to get. I've heard great things about royal purple, but I'm unsure if I need to have FM added. Some people say yes, some people say no. Also, I don't tow very often, a few times out of the year.

I know there are plenty of threads out there, but all I need is a simple list of things to get.

Thanks in advance!

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Unread 08-04-2011, 07:12 PM   #2
Best4x4
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The Royal Purple is a Full Synthetic and you shouldn't need to add anymore LSD additives. I was using RP in my 05 Rubicon until I recently removed the diff cover to repair a leaky air locker hose. I went with the cheap Full Synthetic that Wal-Mart sells at 11.50 a jug vs 19.00 for the RP Full Synthetic.
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Unread 08-04-2011, 07:29 PM   #3
WiCkeDuDe
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I run just the RP with no extra FM and have had no issue. The FM in the RP is sufficient for quadradrive even.
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Unread 08-04-2011, 08:15 PM   #4
straty1987
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i ran RP with the FM for limited slip and i need to add some FM, i used the mopar FM since i oicked up some with the 247 fluid.

put RP in, if you get sounds just add soem FM
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Unread 08-04-2011, 08:35 PM   #5
wsar10
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If you hav the D44 rear than you need to add a FM, I would go to the "stealer" and get the MOPAR FM.
http://www.wjjeeps.com/tcases.htm
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QUOTE=billzcat1;wsar10 is right on point on this oil thread - as usual. Anyone reading this would be well-served taking his advice.


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Unread 08-04-2011, 08:44 PM   #6
WiCkeDuDe
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What sounds are you refering to?
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Unread 08-04-2011, 08:59 PM   #7
metalhead
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Royal purple is the best stuff. I use royal purple for all the fluids exept oil because oil gets changed more often than the other fluids so its too expensive to use their motor oil. If you have the dana 44 with LSD than you may need to add some fm if you get any noise from the rear on sharp turns at slow speed. I have it but didn't bother with the fm but when I change the fluid I may add some this time.
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Unread 08-04-2011, 09:03 PM   #8
straty1987
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Quote:
Originally Posted by WiCkeDuDe View Post
What sounds are you refering to?
when you make a sharp turn at slow speeds sometimes the tires will screech if the FM is not right in the Diff with Limited slip
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Unread 08-04-2011, 11:34 PM   #9
Best4x4
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My 05 Rubicon has an Dana 44 with LSD and I run straight RP 75w140. Zero issues and I had the RP in for close to 25K and it still looked clean and purple. On the RP and Mobil1 bottles they say fully compatible with LSD.

I've never had the rear end of my Jeep chatter with the RP/Mobil1 or Lucas 80w90/75w140 diff fluid. On my old 89 Mitsubishi Montero's with a LSD they did chatter and required an LSD additive, but at the time I also was running straight dino 80w90 gear oil vs full synthetic.
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Unread 08-04-2011, 11:41 PM   #10
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I use RP in My diffs on My WJ Quadradrive, Had to add some mopar FM to Get rid of the chatter/bindings in the diff.
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Unread 08-05-2011, 09:20 AM   #11
WiCkeDuDe
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Strange, I get no tire lockup or chirp with straight RP, but then again im on 32s.
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Unread 08-05-2011, 11:27 AM   #12
billzcat1
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I'm not a big Royal Purple fan, but it all comes down to what 4WD system you have. The JKs use a different LSD so there's no point comparing the two. If you have Quadra Trac II, you do not need friction modifier of any sort as there is no limited slip differential to worry about.

Also, just because a fluid is synthetic does not mean it has FM or is compatible with QuadraDrive. The only two fluids known to be "good to go" right from the bottle are Redline 75W140 GL5 and Amsoil SevereGear 75W140. I prefer the Redline.
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Unread 08-05-2011, 11:44 AM   #13
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Quote:
Originally Posted by wschilawskiw View Post
Hey all,

I have an '02 4.7 with Quadra-Trac II. I'm looking at changing the differential fluid and I'm wondering what to get. I've heard great things about royal purple, but I'm unsure if I need to have FM added. Some people say yes, some people say no. Also, I don't tow very often, a few times out of the year.

I know there are plenty of threads out there, but all I need is a simple list of things to get.

Thanks in advance!
It would be very rare for a 2002 Quadra-Trac II WJ to have a Vari-Lok rear (LSD) differential. It would have had to be ordered and it would have been an extra cost option. Normally only Quadra-Drive WJs were certain to have Vari-Lok differentials. All WJs with the 4.7 came with the D44a whether it had Vari-Lok or not. Only Vari-Lok equipped differentials need FM.

If you remove the cover to drain the old lube, as most people do, a Vari-Lok differential will look different than an open differential. That would definitely tell you whether or not FM is needed. As I indicated above, it is very, very unlikely that your 02 QTII will need FM.
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Unread 08-05-2011, 12:08 PM   #14
wsar10
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Well gents all this talk about diff's prompted me to check my records and I have not done my rear in 20k mi.
So i just ordered up some AMSOIL extreme gear 75w140 and will be doing it tomorrow, got it for 15 bucks a qt. at my buddy's 4x4 shop.
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QUOTE=billzcat1;wsar10 is right on point on this oil thread - as usual. Anyone reading this would be well-served taking his advice.


-03 WJ laredo 4.0 120k a few minor mods
-93 XJ 5spd, 3" zone lift
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Unread 08-05-2011, 05:00 PM   #15
Best4x4
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RP says right on the bottle Limited Slip/Posi-Track.....

From Royal Purple's website:

Quote:
"All viscosities of Max-Gear are formulated with hypoid friction modifiers necessary for use in clutch or cone type differentials. No additional additives are necessary."
And who is talking about JK's?? My 05 IS NOT a JK lol
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