Front & Rear Diff, What fluid?

[TKarnas]

Ok I searched and searched these forums and everyone uses something different. But I need to replace the fluid in the front and rear differentials.

I have a limited slip rear not sure about the front.



Some guys say synthetic is the way to go some say no use standard with additive for limited slip.



I know if the truck came with the standard oil with additive I can not mix it with synthetic fluid.



How do I know what type to use? DO I need to run my vin or something to find out what OEM put in?



Thanks

 

[SSalzer]

I'm pretty sure I've read on here that the fluid from the factory is a synthetic blend. If it's any consolation to you, I put Amsoil Severe Gear in both my front and rear without any problems.

 

[TKarnas]

thanks... were can I get Amsoil from? If any one else helps me, please let me know were you get the fluid you use please. I have Advance Auto parts, NAPA and walmart, of course the dealer. I really dont want to spend the $$ for the dealer.

 

[Jim W]

I ordered my fluid on line through the Amsoil site. I received my order in three working days from the time I ordered from Amsoil. This site also provides the approximate amount you need for each Diff just follow the instructions. AMSOIL Products - Auto and Light Trucks Lookup - amsoiloaf. 1769688

 

[DaveHess]

I'm pretty sure the factory fill is a full synthetic fore and aft. For the record, I use Redline 75W-90 Front and 75W-140 Rear. I use Redline in my drag car and have never been let down. I had an 8-3/4 fail in the car while running Amsoil so I will never run it again. Just my . 02. I use Shock-Proof Heavy in the drag car.

 

[TKarnas]

can any one tell me what size rear and front I have? will the glove box codes tell me this ?

 

[TKarnas]

Also forgot to ask... everyone seems to agree its Synthetic but do I need to add a posi additive? or is the synthetic already have it included? Sorry for the stupid questions but I really dont want to mess up the rear on the truck!

 

[steved]

Probably a 9. 25" AAM front and a 11. 50" AAM rear... no limited slip modifier is needed unless you experience chatter (unusual)...

The OE fill is 75w90 synthetic, front and rear.

 

[TKarnas]

Heres the funny thing... . called my local dodge dealer. Spoke with service to get a price on having them do the work... They did not know what oil they put in quoted me $400 which should cover the work. When I asked if this included the limited slip adder they said yes, but when I questioned him why the owners manual said I did not need it he could not answer my question! Then I transferred to parts to ask for the price of the fluid they could not answer me what was in it..... I think its time to look for another place!

 

[steved]

Changing the fluid is fairly easy... if you can change oil (or brakes), you should be able to handle the diffs.



They use a rubber-over-steel gasket that is reused... no sealant is required.



Remove all the bolts holding the cover on... that drains the oil.



Clean the surfaces, reinstall gasket and cover, and fill the diff with a 75w90 synthetic... nothing difficult.

 

[AH64ID]

Probably a 9. 25" AAM front and a 11. 50" AAM rear... no limited slip modifier is needed unless you experience chatter (unusual)...



The OE fill is 75w90 synthetic, front and rear.

Correct, and since the LSD is a helical gear unit you should never need modifier as it won't do anything to the LSD. .



AAM (the maker of the axle) says that the 11. 5 axle preforms better on 75w-90 than 75w-140 in all conditions except towing at or above GCWR thru death valley in summer...

 

[steved]

The LSD is not a true helical in the sense that it still has clutches. Look at the diagram from the FSM, they are termed "shoes".



That's the reason some people experience chatter...

 

[AH64ID]

The LSD is not a true helical in the sense that it still has clutches. Look at the diagram from the FSM, they are termed "shoes".



That's the reason some people experience chatter...

Hmm. . i'll have to look at that when I get home. . here is the AAM info page on it with a cut-away diagram. .

 

[pullya]

DON"T pay the dealer $400 to change your fluids. You can get all the help and advise you need right here. For $400 you can probably get one of those Dodge guys at the factory thats fix'n to get layed off, to come to your house and do it for you. :-laf

Jay

 

[steved]

Hmm. . i'll have to look at that when I get home. . here is the AAM info page on it with a cut-away diagram. .

OPERATION

When one wheel begins to spin the pinion gears on that side are forced toward the pinion brake shoes. The pinion brake shoes then cause frictional drag on the opposite pinion gears and the side gear. These friction forces transfer the power to the opposite wheel. Once the frictional forces are overcome, differentiation will occur. The torque will be continually biased by the frictional forces to the high traction wheel.


From the Dodge 2004 FSM, page 3-158, Rear Axle.

 

[EDankievitch]

Any one notice that the dealer has two 75-95wt oils, both are synthetic blends but one is very expencive... ... ... . Which one do we use????????

 

[steved]

Any one notice that the dealer has two 75-95wt oils, both are synthetic blends but one is very expencive... ... ... . Which one do we use????????

The full-synthetic you buy at the store... it cheaper!

 

[TKarnas]

Okay so now that I am still confused..... I live in PA so I do not see extreme heat but I do get some cold days in winter. I do not tow extreme amounts, maybe 1 ton trailer at most.

So this is what I am thinking.....

75-95w Full synthetic blends mybe aimsoil, Mobile 1 ?? . Get the friction adder to be on the safe side from Mopar.

How many quarts do I need? I hear any were from 3-4 front and 4-5 rear... stock covers

 

[steved]

75w90 in a quality synthetic will be fine... everyone has their favorite. Run a name brand and you should be fine... these differentials aren't as delicate as Dodge seems to indicate in that 15k change schedule.

Nix the synthetic blend. Just buy a full synthetic... Mobile 1, Amsoil, Royal Purple, Redline, even Lucas offer full synthetic gear oils. Dodge lubricant specified in the 2004 FSM:


REAR AXLE

10 1/2 AA - Mopar Synthetic Gear Lubricant 75W-90

11 1/2 AA - Mopar Synthetic Gear Lubricant 75W-90

NOTE: Trac-Lok differentials require Limited Slip Additive in the lubricant. Trac-Rite™ differentials DO NOT require Limited Slip Additive.



Nix getting the LSD additive, I would only buy it if you find its needed (ie you get chatter). Most synthetic gear oils already have some LSD additive in them. As noted above, the Trac-Rite does not require it.

The FSM indicates 4. 75 pints (2. 5 quarts) for the front 9. 25AAM and 7. 65 pints (4 quarts) for the rear 11. 50AAM. I would buy at least one, if not two, extra because they always seem to hold more than indicated.

Where in PA are you located??

 

[TKarnas]

okay all... . Two dealers ran my vin and both told me 10. 50" rear and 9. 25" front. Both told me 75-90w fluid but disagree on the rear adder... . Is there a site I can confirm that the rear is 10. 50"?