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Front and rear diff. fluid


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Ive lost some links to stuff whenever i got a new computer here a little while back, needing to know what kind and how much gear oil for my front and rear diffs. I think i used to have a link to a chart or somethings listing the amounts and types of fluid for the whole truck. Dana 60 in the front 80 in the rear. Thanks for the help-Jordan-

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Decided Im going to put on a magtec rear diffCouldnt find SAE 80W-90 gear oil.Found 85W-145 gear oil.Any problems running with that - and how do you know if LSD without jacking tires ???Im an auto so Dana 70 and guessing it has LSD.

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Decided Im going to put on a magtec rear diff Couldnt find SAE 80W-90 gear oil. Found 85W-145 gear oil. Any problems running with that - and how do you know if LSD without jacking tires ??? Im an auto so Dana 70 and guessing it has LSD.

85-145 is a little thick unless you're towing heavy or live where summer temps are regularly over triple digits. Most people dont know that thicker oil runs hotter than thinner oil too because of the hypoid friction. You may also notice a little loss in mileage as well running the thick stuff. If you dont tow heavy then you'll be fine with 80-90 or even the 110 weight. But whatever one you choose, I'd always suggest running synthetic. Todays trucks are bigger, heavier, and run more HP than older trucks and thats not even accounting for the additional HP we add over stock. Thats not to say that regular oils cant handle that but giving the extra edge of synthetic in drivetrain is worth the money.
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Depending on what you buy, some brands of gear oil already have friction modifier in the lube for limited slip units so there's no need to add any more. I cant speak for most brands but I do know that Amsoil and Royal Purple have the modifier already.

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Somewhere on here, I posted the info from Royal Purple (an email from their Tech Sppt) about what to use, should you want to go with their stuff.

If you can find it, I'd really like to see what they said too.
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If you can find it, I'd really like to see what they said too.

[h=2]Posted Image[/h]

From Royal Purple's tech sppt :

For your 2001 Dodge Ram 2500 Cummins we recommend the following:

Transfer Case: Royal Purple Synchromax (part #01512, quart bottle); 5.2 quarts;

(w/241HD w/ power take off)

Front Differential: Royal Purple Max Gear 75W-90 (part #01300, quart bottle); 4.25 quarts;

Rear Differential: Royal Purple Max Gear 75W-90 (part #01300, quart bottle); 5.05 quarts;

Power Steering: Royal Purple Max EZ (part #01326, 12-oz bottle);

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Thanks KATOOM for the link, thats exactly the old link i had but i just couldnt remember the site. As far as fluid goes we have some Castrol Syntec 75w90 at work that Im going to look up the info and specs on to see if i want to run it or not, and see if it already has the friction modifier in it or not.-Jordan-

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cool, let us know :)

--- Update to the previous post...

From this morning:

Good morning, Jim.

You informed me awhile back on what RP fluids to use in my 2001 Dodge Ram Cummins 6 speed (NV5600) 4WD.

Do the diff fluids require a friction modifier (truck is equipped with LSD differential) when using your Max Gear?

Thank you,

Rick Wall

Good morning Rick,

No, RP Max Gear includes the friction modifier additive for the limited slip differential clutches. If for some reason your differential seems to prefer a higher dose of friction modifier than what is included, (as evidenced by a shudder on slow tight turns) then there are some steps that can be taken to easily remedy the situation.

After the initial filling of the differentials with Max Gear for the first time, drive to a nearby parking lot and do 5 or 6 slow tight figure 8s. This works the new fluid in and forces fluid in between the clutches so they can be treated with the FM additive.

If after a period of highway type driving, you experience a shudder or noise upon making a tight slow tight turn, this would be an indication that your differential is one of the few that seems to prefer a higher dose of friction modifier than what is included in Max Gear.

At this point you can purchase some additional friction modifier from either your local Dodge/Ram dealer or some aftermarket limited slip friction modifier from your local parts store. Do not add the whole bottle since you are just trying to increase the dose that is in there already so as to be in the sweet spot. Just add about 2 ounces and re do the figure 8 procedure. This should take care of the shudder if it occurs after the initial fill. If it does not repeat the small dose adding of 2 ounces per treatment and redo figure 8s until he shudder is gone.

If you have any additional questions you can also call toll free at 1-888-382-6300 and just ask for Jim in tech.

Thank you for choosing Royal Purple and have a great day!

Jim Morrissey

That's some pretty good tech support, right there.. :smart:
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