Rear Differential Fluid

[8UWITH6]

Did a search didnt really find what I was looking for. I just wanted to make sure Royal Purple 75W90 Full Synthetic gear oil would be okay for my new to me Mercury. I run it in my Buick with the GM additive and have had no problems. Does the Mercury need an additive or can I just drain and refill with the Royal Purple Full Synthetic gear oil? Thanks guys!

[marauder410]

im not 100% but sure some1 will chim in but no that was originialy designed to go in our cars but they charged it to 75w-140 and i just did a change and thats what i used

but ur correct on the addisive if you have royal purple thats the ****nit and you dont need to add the friction modifier it is already added in withthe royal pruple so its just a drain and fill

[8UWITH6]

oh, just to be clear I wont be adding the GM additive to the Merc. Just need to know if the Royal Purple 75W90 is good, vs 75W140, and if I even need a friction modifier (additive). THANKS GUYS

[MyBlackBeasts]

75W140 required

Check with RP CSR or someone who knows the product about FMA requirement

[ajdereicup]

I used RP 75w140 in my car. Said it had friction modifier in it already. Over $22 a quart = :( but I wanted the best

[fastblackmerc]

75w140 is the correct weight.

Like oil, use a good quality synthetic fluid. Almost all synthetic fluids do not need friction modifier added.

[ctrlraven]

I use Mobil 1 75w140 LS gear fluid. The LS stands for "limited slip" so it does come with the friction modifier already in it. 3 quarts is all that is needed.

[8UWITH6]

Ok. Darn. Had this stuff on the shelf. My computers at work state 75W90. But if you guys say 140 Ill get some! :) Thanks.

[fastblackmerc]

Ok. Darn. Had this stuff on the shelf. My computers at work state 75W90. But if you guys say 140 Ill get some! :) Thanks.

Ford changed the spec when they found out about the soft axle issue.

[Murked03']

Hey Neil congrats on the purchase did ya finally get rid of the Impala???

[8UWITH6]

Makes sense. Thanks fellas.

[8UWITH6]

Not yet. Had a guy drooling over it Monday, supposed to come look at it again Friday. Another guy called me last night to come look at it today at my work. We will see.

[Murked03']

Man you held out for awhile and found a DBP I'm like so jealous right now! I'm pretty sure the blues bros will seek you if they haven't already post pics asap!!!

[DOOM]

I use Mobil 1 75w140 LS gear fluid. The LS stands for "limited slip" so it does come with the friction modifier already in it. 3 quarts is all that is needed.

This!!! ^^^^^^

[8UWITH6]

Pictures of the car are in my marauder wanted topic. Check it out

[bill64]

Pictures of the car are in my marauder wanted topic. Check it out
i checked out the pics...nice car!!! the mm is a lot of fun to drive, i just got my first one two months ago, had to travel a little for it but it was worth it. the first thing i ordered for mine was the ford limited production cert. nice document to have with the mm

[montyd]

i put royal purple in mine with an eaton differential. not the thing to do! now im paying for it and cant get the stupid thing to quit chattering at low speed and am about to change the fluid again. so what im saying is if you run an eaton posi unit, 80-90 gear oil is what you need to have per eaton lol

[justbob]

I use Mobil 1 75w140 LS gear fluid. The LS stands for "limited slip" so it does come with the friction modifier already in it. 3 quarts is all that is needed.

I used the same crap two changes ago and guess what started chattering really BAD a couple weeks later??? Yup, I had to add FM! What a waste of money. Sorry, but I was pissed because I had just installed new clutches. Never again.


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[8UWITH6]

Hmm, what do I do then.........

[screamn]

Better add the friction modifier to be safe......

I used valvoline synpower plus the ams oil FM additive and all is well.

[justbob]

Hmm, what do I do then.........

Look above, I was commenting on Mobil1, not royal purple. Many members here have had excellent results with RP.



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[8UWITH6]

I just want to do the job correctly, once. Until I do gears. Looks like I need 75W140. No problem. Factory I assume is regular GL5 conventional. I am not against synthetics and use Royal Purple in the rear diff of my Grand National with no issues. I prefer Valvoline, Mobile 1, or Royal Purple Products. The car only has 30K so it cant be too messed up. So I guess the question is friction modifier or no friction modifier? Correct? Thanks fellas, you all rock.

[fastblackmerc]

I used Redline and NO fm.... quiet for the last 55k.

[guspech750]

I used the same crap two changes ago and guess what started chattering really BAD a couple weeks later??? Yup, I had to add FM! What a waste of money. Sorry, but I was pissed because I had just installed new clutches. Never again.


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LOL!! Same here. Remember when you changed my clutches before Louisville a few years back? I too had just used Mobile One with the Friction Modifier supposedly in it. And look where it got me. I had to order new clutches and a trip to Justbob Motorsports, (which is cool to be at). Never again with Mobile S,H,I,T, Y One for my rear differential.


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DTR + 4.10's + Eaton swap = Wreeeeeeeeeeeeeeedom

[yjmud]

I like my rear end no more modifier

[ajdereicup]

Many members here have had excellent results with RP.

But hurt wallets:(

[marauder410]

But hurt wallets:(


ROYAL PURPLE is kinda of expensive but nothing but the best is used in my marauder

i got my 3 quarts off ebay for 42.00 what was a awesome price because in advanced auto parts the RP is 22.00 a quart :eek:

but like ALOT of members here has used it and never heard nothing bad from it and NO you DO NOT need to add friction modiifier in it, it is already included and says so on the bottle... so just pour in and let the tires spin :burnout:

RP has saved me a ton of money and saved my rear end becasue when bought my MM my car had the one wheel peel and had fluid in it and i did a rear dif fluid change and it's a miracle after i chnaged the fluid to royal purple 3 quarts NOW both wheels spin again like a new rear end.... i was soo happy and AMAZED that just doing a fluid change would fix my pone wheel peel...so ROYAL PURPLE FTMFW.....:banana2::banana2:

i love royal purple and use every brand fluid they make and is used in my MM....oil every 3k because drive my car daily and drive it hard,rear end diff fluid, transmission fluid and if you think the rear diff fluid hurt ur wallet then dont even think about using it in your MM lol bec our car takes what 10 quarts at 14.99 a quart :eek: but likei said it performes better than any other fluid brand out there by far and no! will chnage my mind or make be use any other fluid EVER.....155.00 for the trans fluid al together but nothing but the best luid wise wil ever hit my MARAUDER she deserves the best availible

so use RP and dont have to worry abut changing it for a long time OK and just get 3 quarts and pour it in and dont ADD nothing else and that should awnser all your question ok buddy enjoy your rauder and do lots of :burnout::burnout::burnout::D

[justbob]

LOL!! Same here. Remember when you changed my clutches before Louisville a few years back? I too had just used Mobile One with the Friction Modifier supposedly in it. And look where it got me. I had to order new clutches and a trip to Justbob Motorsports, (which is cool to be at). Never again with Mobile S,H,I,T, Y One for my rear differential.


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DTR + 4.10's + Eaton swap = Wreeeeeeeeeeeeeeedom

NOW you tell me what fluid you/they used? LOL I almost forgot about getting all up in your rear!


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[8UWITH6]

I have 4 quarts of 75W90 Royal Purple in the garage. I am going to take those back to my local parts guy (do a lot of business with him) and he said he will take them back and swap me out for the 75W140 Royal Purple. Thanks fellas. I appreciate your help.

[tbone]

It only calls for 1.8 liters or 3.75 pints which is about 2 quarts in the owner's manual. So when I took my car to Ford to install 4.10's, I brought 2 quarts of Mobil. They said it takes three, and charged me for another one. Sooooo, I go to change it myself this summer, and it wouldn't even take the entire 2nd quart, especially after the friction modifier goes in first. Don't waste your money buying three, and don't let the dealer/shop scam you.

[8UWITH6]

Doing it myself. No worries.

[DOOM]

LOL I almost forgot about getting all up in your rear!


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Damn biscuits! :eek: :eek:


Joe in other words bob is saying you we're nothing special! :D

[guspech750]

Damn biscuits! :eek: :eek:


Joe in other words bob is saying you we're nothing special! :D

Oh mannnnnnnn :(


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DTR + 4.10's + Eaton swap = Wreeeeeeeeeeeeeeedom

[marauder410]

when i did my fluid change and took the cover off and checked everytthing and cleaned it all up and when put back together it took 3 quarts no problem

[Vortech347]

Everytime I've tried a "friction modifier not required" bottle. The dif is loud as hell until I throw in some FoMoCo Modifier.

[justbob]

Two quarts here.spills right on out.


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[MyBlackBeasts]

Two quarts here.spills right on out.


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Depends on what cover you have. With my FOMOCO racing girdle mine uses approx 2.75 qts.

[marauder410]

oh yea forgot about that i got the ford racing cover so i guess thats why mine held the 3 quarts no problem i guess

[8UWITH6]

STOCK 30K mile car.........2 qts should be cool............ Royal Purple 75W140 on the shelf.......... ready to go :)

[ajdereicup]

I got 3 in mine? But have a different differential cover. Well a little less then 3 because I spilt some on myself...

[tbone]

Stock: 2 quarts.
Ford Racing cover: + Fluid which I indicated before in a different thread.

I guess it doesn't matter until it jizzes all over you.....

[GreekGod]

If you want to do it right the first time, go with an Eaton Truetrac & 31 spline axle shafts. No clutches to wear out. No spring to hassle with.
re:
http://www.eaton.com/Eaton/ProductsServices/Automotive/AutomotiveAftermarket/Differentials/PCT_221471

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