I'm going to change my diff oil but before I do I want to make 100% sure I have the drain and fill plugs located, I've attached a picture of what I think is the fill and drain plug, I know it might be hard to tell from the pictures but if anyone knows can you please confirm I have them right.

Also would anyone know what size tool I need to open the plug?

 

it takes a huge allen head socket, forgot what size exactly... but its big
you have the plugs right

 

Thanks dude, I've watched a few youtube videos where they actually have to remove the housing and drain the diff, then reseal it and put it back together. Im glad Mercedes was smart enough to install a few plugs!

 

soak the plugs with pb blaster or some sort of penetrating oil before you attempt to remove them. They corrode and have been known to strip before they come out. If that doesnt work heat the case around the plug with a propane torch, that will pretty much break up any corrosion

 

I bought a whole set of metric allen head sockets at Harbor Freight for around $10 and they worked great during my diff oil change. Make sure that you can loosen the fill plug before you remove the drain plug or you will have a problem refilling if it's seized up.

I had to buy a pump-style oil can to refill it as there is no way to get a bottle up there with the tight clearance. It took approximately 1.5 quarts to refill until it started oozing out (I used Valvoline 75w90 synthetic in mine). The original fluid looked quite dirty after only 10k miles, and measuring the fluid showed it was 1/3 quart low from the factory.

 

I was looking at running a diff pump and differential cooler the keep the rear-end temps low. I'd have to imagine fluids get rather hot with these cars, considering the exhaust runs right underneath it.

Think you could maybe figure out what thread pitch the plugs are for me?

 

if you have an advance auto on the island they have a small hand pump that fits on the top of the gear oil jug. it allows you to pump it in as you cant tilt the jug into the opening.
i run mobil 1 75/90 and havent had any issues with the synthetic oil

 

I just grabbed some redline 75w90 and will be doing this as a weekend project.

 

I couldn't find the correct size allen wrench for my old Mercedes so I looked in my used bolt drawer and found on that had the right head size and put some nuts on the end with a lock washer and used that to get the plug out. Naturally, I was very young when I did this, but it worked. Back yard engineering at its finest.

Les

 

the plugs on the rear diff arent allens. they are 13mm(i think thats the size) square heads. socket extentions are the wrong size to fit but harbor freight has a set for about 15$ that has the right size bit thats works great

 

the pics above do not look like squares to me..........

 

my apologies mike!! i just went out and climbed under the car and tried the bits. 14mm hex head!! long day and im suffering from old guy diesease!

 

I think I got you beat on the old guy part..... I 'thought' about going and looking under the car.... then decided to look at the pics instead.....

 

i looked at them! just see blurs now. eyes are friggin shot. need some new ones!

 

Come on you guys, I have 20 magnifying glasses of every size. Don't be stubborn, give in to the reality.

Les

 

Hrmmm I'm extremely confused now and I need your expertise to help me out lol

I called my local Chrysler dealership to book in a diff oil change, now the guy I spoke to seemed to be very knowledgeable, he called Chrysler directly and received confirmation that the diff is NOT LSD and it doesn’t need any special additives.

I called up a bigger Chrysler dealership just to double check this guy knows what he's doing, and they told me that they know it's not LSD but it still needs the additive, he said its to do with the type of DIFF and the locking characteristics of it. I proceeded to called another 2 dealerships and they both told me it needs the additive.

Now back to my local dealership, he said the oil they are using is directly approved by Chrysler and it's mineral based, does this sound right? I thought fully synthetic would be required. I'm thinking of calling and cancelling my appointment because I don’t know who to trust now lol

 

Just use a good synthetic like REDLINE. It meets the additive requirement so there is no need to worry about it.

 

Thanks man, the only thing is there doing the oil change for me so I dont get a say in what oil they use, Maybe I might cancel the appointment buy some redline and do it myself lol..

You know what they say. when you want something done right, do it yourself!

 

Most places will install the oil you provide and only charge labor fees in you wish to bring your own oil.

But doing it yourself if always preffered IMO.