Servicing rear diff fluid, what to use!

[Ilikeoldfords]

Ok guys. I know this one has been hit before but I am having a hard time finding the old threads on it.

 

My question is this. What fluid should I use? Is a new gasket required when putting the cover back on? Do I need any additive do go with the fluid? I dont believe I have limited slip. One tire will spin freely on slick surfaces anyway.

 

This is on my 01 ram 2500. Dana 80 rear end with 3.55's.

 

Thanks for any tips!!

[98whitelightnin]

I use house brand 75w90 or 80w90. No additive needed if you don't have limited slip. Use some good permatex and be done

[Hawkez]

I'm getting ready to do this as well so I'm also interested in the replies.

[Mopar1973Man]

I grab my modified 5 gallon bucket slip it under the the differential. Unbolt the cover and carefully pry the cover off. Allow the old fluid to drain out. I've always just used a bead of standard silicone around the cover. Now after working for Lindy for nearly a year I tend to like the grey Silicone now more so for the differential covers. Then I grab my 5 gallon bucket of 80w-90 gear lube with bucket pump and fill the differential. I typically cover half the hole with my thumb and pump in another 1-2 pumps and quickly throw the plug back in. I do this so there is plenty of gear lube to flood the bearings on the axles again after draining.

 

As for the Internet myth of over filling causing seal issues. I can answer that. Typically when we see those coming into the shop with leaking axles I can just about bet the differential vent is plugged with mud or grime. When the differential warms up and fluid expands there is no vent so it pushes oil out the seals. So over filling will not cause seal issues.

[rancherman]

I went with Mobil 1   75-140   'LS'.       Both  front and  rear.    8 quarts total,    iirc  3.5  front,   4.5 rear.          and    Permatex    'Right stuff'    on the covers.

[rancherman]

I agree too with Mike on the   seal leaking!     if  the  dang  seal  is going to leak..  it's because  it's  either shot, or  the   vent is  plugged.     Draining it  so  leak quits  is just  dumb..

 

 

Around here,    when  something  suddenly  stops leaking..  it means   its  out of  oil!  

[Hawkez]

As for the Internet myth of over filling causing seal issues. I can answer that. Typically when we see those coming into the shop with leaking axles I can just about bet the differential vent is plugged with mud or grime. When the differential warms up and fluid expands there is no vent so it pushes oil out the seals. So over filling will not cause seal issues.

 Where is the vent?

[Ilikeoldfords]

 Where is the vent?

 

Should be on top like where the brake line tee is. Should be a rubber hose coming off of it going up towards the pickup box.

[AGPTurbo]

Where is the vent?

Well, mine is zip tied up near the spare now since it mysteriously began dragging on the road . Must be a factory clip that holds in near the fuel tank somewhere

[Dieselfuture]

I got a mag cover on rear and I put 8 qt in of 75-110 amsoil with couple of small LS additive bottles, you'll be able to see if you got LS when you take cover off. P.S I love this mag cover been 4 years and about 15k of mostly towing and dipstick is magnetic and every time I check it barely has any black on it and oil is still clear. I also noticed pumpkin is a lot cooler, whether it's synthetic oil or the 8qt that I'm running.

[CTcummins24V]

For limited slip, the manual states 75-140 synthetic for the rear with at least one bottle of limited slip additive. The first time I did mine I needed 2 bottles to prevent chattering. This last time it was 3 bottles, Mopar brand only, any other off the shelf additives will not work, well at least for me. The front might only need 75-90. Permatex whatever, right stuff worked for me this last time, I think I used gray the first time.

[IBMobile]

I did mine about 30k ago with 75-140 synthetic with 1 bottle of additive. I use Permtex®  Ultra Black®  on just about every thing I put together.

Edited February 24, 2015 by IBMobile

[Wild and Free]

The "Right stuff" by permatex is the best stuff on the planet. Nice thing about it is it displaces oils and will seal unlike any other silicone style sealant where if the area being sealed isn't 100% dry and clean it doesn't stick and will not seal.

[Hawkez]

I know this is going to sound like a silly question to many of you, but do some of the 2nd gens have limited slip diffs and others don't?  How can I tell what I have?

[Wild and Free]

Not a generational thing or brand thing at all but to narrow it down to second gens assuming it has a factory limited slip unit it is a clutch type.

If you are not sure if you have a limited slip or not easy way to check is to jack up the rear end and with it in neutral rotate one rear wheel, if it is a limited slip both wheels will turn the same direction, if it is an open differential the wheels will turn opposite of each other.

Or leave it in park while jacked up and if you can not turn one rear wheel you have a limited slip and if you can easily turn the wheel and the other turns opposite you have an open diff.

[Hawkez]

Thanks, I just read your post on the other thread where you explained this. 

[IBMobile]

When you have a question such as axle size or type call the dealer's service department and give them the Vin#. They can look it up and tell all the equipment and options that was installed. 

[AGPTurbo]

Check the glove box door tag as well. 

[rancherman]

If you still have  the  tag...

 

Take  the   BOM   (bill of  material)   number  off of it.   then  go to this site

 

http://www2.dana.com/expertforms/deabill.aspx

 

 

 

and   type in your  BOM.     You'll  get a  list of  EVERYTHING you ever wanted to know  (parts lists,  differential,  gear ratios)   about  that  particular axle!

[Ironforger]

I thought I read somewhere that the dana 80 is a limited slip axle. That is ALL dana 80's are limited slip.

 

Regardless, I used permatex ultra grey and put in 80w-90 GL5 with 2 bottles of friction mod when I installed all new rear bearings last year, since the previous owner had an outter wheel bearing go bad to the point where the axle shaft was grinding into the axle tube.  He replaced it with a cheapo bearing so i decided to do the right thing and install complete a set of timkens, as well as spindle flat locking washers (eliminating the nylon insert lock nut & lock wedge). Got the whole kit from quad4x4.com   Good price, great customer service.

 

 

 

 

Bottom line is, I'm lucky I was able to save the axle. I don't know why the outer bearing went bad, who knows maybe he was low on lube. Regardless, i'm not taking chances. I'm soon going to change the lube and put in a slight overfill of synthetic 75-140 & a couple bottles of oem friction mod.

 

BTW, taken from the owners manual. Ironically, this page is from the "Towing" section of the manual, not the maint & lube section.