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JohnsonUSAF 04-13-2010 03:25 AM

Differential oil question
Some of the higher end oils already have friction modifier. Would it be safe to use the royal purple with the friction modifier only? Or would you still add Mopar modifier?

Also if you did "double duty" and add both, would there be adverse effects?

John_R 04-13-2010 10:10 AM

Re: Differential oil question
At the auto parts store, they sell that limited slip additive in a 5 oz. bottle (iirc) and I want to say it's called TransX. I always add that to my LSD and even did on my GTO, which called for a GM spec number; never had any issues. I know many of the oils claim to have LSD aditive built in, but in my experiences, it's never sufficient. The way you can tell is go on the freeway for awhile, get it warm, then go in the parking lot and do some'll feel like you're on square wheels :D

I'm not 100% on the scientific reasoning, but if I recall, the additive simply thickens it up to be able to cling and stay on the clutches and such in your unit. So, you'll be OK adding it, just don't go wild.

hobbes630 04-13-2010 05:54 PM

Re: Differential oil question
So I got a differential oil question too hoping the experts here could give me their advice too.

I have an 05 Grand Cherokee 4.7 L 4x4 with Quadra-Trac II and the conventional differentials. I was planning on changing the oil and using Royal Purple Max Gear (75W140) Synthetic Gear Oil which I've read some really good reviews on. Now I know the royal purple already has the limited slip additive in there already but the additive is not required on the conventional differentials. Would I be safe using it on the the regular differentials anyways since it has the additive already in there? Does it do any damage or something like that?

What do you guys use on ur conventional differentials? Anyone who uses royal purple ur input is appreciated...

John_R 04-13-2010 06:06 PM

Re: Differential oil question
I would think you'd be alright. IIRC, I used RP in the front diff of my 5.9 (ZJ) without issue and know I used it in the rear, but added LSD additive for that, as mentioned above. Personally, I think a conventional, quality gear oil would be fine, so long as you change it on a regular basis (like maybe less than 30k of easier driving) and would be much less money. I am debating on whether I will use regular oil or synthetic on this WK (has the F/R 'lockers'). I just wasn't sold on the extra $$$ of syn in my ZJ (for instance) and esp. RP...only reason I went with it on the GTO is because everything came with synthetic from the factory (I was the original owner). Crap gets to be a lot of money and can imagine front/rear diff, trans and transfer case + 7 qts. of oil!

DJ BoNiOmArIo 04-13-2010 06:11 PM

Re: Differential oil question
for the QTII it is recommended that u do add the limited slip WK jeeps has the specs on how much to add and just add that much along with the RP to be on the safe side ...

mine is QTI and I still used the RP with limited slip additive and yes as John_R did mention on his first post it is to thicken the oil a tad bit so it can cling on the gears easier and have less wear on it just don't add too much

hobbes630 04-13-2010 06:35 PM

Re: Differential oil question
Correct me if I'm wrong here...Quadra-Trac II comes standard with C200F and C213R differentials which are NOT the ELSD. My build sheet says I have conventional differentials that I tells me I have C200F and C213R right?

I thought the limited slip additive is only for the models with ELSD which is standard on Quadra-Drive II. As far as I know the additive is NOT required for conventional I wrong here?

BDP08 04-13-2010 09:59 PM

Re: Differential oil question
i actually was thin king of doing this differential oil change at the dealer but they charge $150.00 and then the tranmission oil change aswell. i think i can get it done elsewhere cheaper. but idk what do you guys think, i normally like to stick to mopar when it comes to services, but ijust dont want to spend all that money either.
any suggestions???

John_R 04-13-2010 10:53 PM

Re: Differential oil question
Screw the dealer unless you like getting ripped off or your under warranty :) I'd go to a reputable shop and save the other half for gas or dinner or something nice. Most of the quality oils you get at the parts store or a good service shop will meet or exceed mopar requirements. Same thing goes for other parts, although there are some areas where a new factory item would be better than an autozone special (like an alternator, etc.)...But you get the idea.

hobbes630 04-13-2010 11:27 PM

Re: Differential oil question
ya screw the stealership at all as much of the work as you can on your own. If you are going to go to a service shop just read some reviews about the place online and maybe ask around and see if someone can recommend you a place. There is no point in spending more money on something the guy across the street can do.

BTW does someone know the answer to my previous itching to do some differential oil changes here :D:D

BDP08 04-14-2010 12:16 AM

Re: Differential oil question
yeah i know, so how much do you think is reasonable to pay for both, the transmission service and rear differential service? just to have an idea so when i go out there looking? and anything i should be aware of, like they told me no one will actually flush the system out but just provide service so not to buy into that if anyone tells me thats what theyre doing. lol thanks for the advice guys.

onorok 04-15-2010 06:54 PM

Re: Differential oil question
If all you're doing is changing the oils, do it yourself and save an ungodly amount. The rear differential isn't hard at all to do and the transmission is easy as well.

Here's a couple vids to get you started:


Rear Differential

On the rear-differential, it's a good idea to remove the whole cover after draining and check your gears for wear, it's not required but it is a good idea.

They really are easy to do if you have the right tools, and you save a helluva lot of money and get the benefit of feeling good about doing it yourself.

BDP08 04-16-2010 06:46 PM

Re: Differential oil question
^^^ thats perfect thanks for the info.

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