Just changed my differential fluid and replaced it with MOBIL 1 Synthetic...
 

Hey.

Just finished the job and it took about 15 minutes to complete. I first opened the top bolt and then the drain one. I could not believe how bad the fluid smelled (literally like crap). It was very very black in color so I don't imagine that anyone has ever changed the fluid in there. I did get one of those squirt guns (don't know the proper name) and filled it with Mobil 1 75-90. The fluid was so different in color compared to the old one, like night and day.

I highly reccomend this maintenence to the car. I still could not believe what stench came from there.

Thanks

On the 240D? How much did you put back in?

Yes, on the 240D. I put probably 1.1 quarts or so.

Does this require one of those large allen wrench sockets? Was it difficult to loosen? (probably not if it only took 15 minutes) Finally, did you tilt the vehicle slightly to improve drainage or was the bolt underneath?

I pulled my 240D diff when I replaced it with the 2.88 from a scrapyard. My 240D has 242,000 miles, and the diff fluid smelled BAD too. The 2.88 did not, but I replaced it with Redline 75W-90 NS.

And you need a 14mm hex socket (Allen) to get the plugs off. Get a good one, those plugs are TIGHT! - I needed my 1/2" 3 foot long breaker bar on the socket to remove them.

I got a set of 3 Allen Head Sockets from AutoZone for 8 bucks. One of them was size 14mm so I needed that for this job. It wasn't all that tight, I put the socket in there and just pulled the hell out of it and it went loose.

The bolt was directly underneath the car. I actually had the car on ramps but in the rear.

[QUOTE=Old300D]I pulled my 240D diff when I replaced it with the 2.88 from a scrapyard. My 240D has 242,000 miles, and the diff fluid smelled BAD too.

Can't smell half as bad as the oil from the lower unit of an outboard :D

Cheers,

Bill

Have been using M-1 on my diff and tranny with very good results, no noise even after 500,000 miles of rough roads. I change my diff fluid at 30,000km and my M-1 ATF in the tranny at 25000km. Have been very happy with this procedure.

does it really make that much of a difference?

I don't feel any difference at all. I guess it just makes me feel better knowing that my maintenence on that part of the car is done. :cool:

There is no performance increase using M-1 as such but the benefits outweigh all the cons if there are any, you get less friction which leads to better mileage, smoother shifting, less noise and best of all, if M-1 is used when the vehicle is new or with a re-conditioned tranny or diff, the life nearly quadruples if the oil is changed and topped up regularly. On off road conditions, M-1 is a life saver in situations where the tranny is taking massive blows and plenty of wheel spin is induced.

What about....
 

what about Valvoline SynPower? I bought some Mobil 1 75-90, but returned it when I got the chance to buy Valvoline, as I am a big fan of theirs. Hoping to change that oil back there pretty soon.

Allthought I know to see If I can get the fill plug off before draining it, I dont know how much should be put in. Does it really make that much of a difference if I err on the side of overfilled? Is there a way to see how much should be in there?

Also what kind should I be using for a 76 300d?

Sorry for the hijack, but I just realized that the diff fluid is at least 10 years old.... :pukeface:

~Nate

I don't think it should really matter if it is overfilled, it's pretty hard to overfill, though DieselGiant overfilled his a tiny bit, that's because his car was sitting at an angle when he filled it. Check his page out, it should be of a little help to you.

http://dieselgiant.com/mercedesreardifferentialfluid.htm

The bottom of the fill hole is the proper level. So, fill it untill oil just starts to spill out, then cap it off.

Diff fluid always smells nasty. Even fresh gear lube, despite its nice color, smells pretty foul.
Any brand of gear lube is better than not changing it, but synthetic is better than conventional oils. I'm sure Mercedes has synthetic gear lube they will sell if you want to be a purist.

I used Valvoline Blend when I did mine about a month ago.
After I had the car on jackstands I used my hydraulic lift to push up and break loose the plug.
I filled it up while it was still on the jackstand so I'm sure a little extra got in there. But like DieselGiant said I'm not that anal to worry about an extra ounce or two.

Didn't notice a difference but I have the peace of mind that it's done.
And yeah those heavy oils really stink, even fresh oil.

Danny

That's why they're called the "rear end" :D

Good to know I need a 14mm hex, time to pick one of those up!

I broke the plugs on ours free the exact same way. :D

I did notice it made the whirring in both car's diff's go away. I'll be changing them again this week as we switched in June to the synthetic and I bet it has pretty much cleaned ALL the varnish off the inside of them by now, so its a good idea in my opinion. They do smell, it smells like natural gas to me...the Mobil 1 Syn does anyways....

You're right.
 

You're right, Mercedes would have a synthetic they would sell you......Valvoline SynPower!!!

I would have never guessed it, other than I couldn't completely empty the bottles into the diff, (due to their size) so I used two partial bottles worth. I then decided to poor the contents of the emptier one together into the more full one. I then put the pour spout back on the now-nearly-full bottle and wiped my spill off of it with a rag. As I finished, i thought to myself, "what a nice little mercedes........LOGO! Sure enough, the pour spout on both my bottles of SynPower (bought at Napa) have MB stars stamped into the lid!!

Go figure?

differential lube
 

Overfilling the differential has two disadvantages:
1) the ring is spinning through more lubricant, with variable power lost.
2) risk of seal failure

I think. lol

I recently put Mobil 1 in my diff, and looked at the bottles in the store. Both Valvoline and Mobil have the same logo on the caps. So, either both have the official MB approval, or it is a mark from the people who made the bottle (both bottles do look the same).
Either way, I think any oil on the market today exceeds the standards that MB had when these cars were new.

to add something(maybe) to this thread, i should ask/say that the wal mart(wherever i get my oil) has their own brand of synthetic gear oil. i was thinking the same thing about my rear differential...

it prolly has NEVER been drained or serviced except when mercedes did it under warranty(if even then)

would i start an oil war(heh heh) if i asked the difference between wal marts bootlegged brand of synthetic fluid and these surely more expensive mobile/valvoline.

also-- does havoline make a diesel rated oil? my father is a fan of texaco products and i have always used havoline 5w 30 in the neon with stupendously normal results. in fact, i have never experienced any difference in any other oil products, i dont understand how anyone can tell.

Texaco makes a diesel oil called Ursa. Hard to find though. Maybe an oil distributor could get it.

I don't see any difference between the Wal Mart brand synthetics and the Mobil, etc. brand.

I'm sure someone will argue that point so I am going to duck now....

Cheers,

Bill

There is very little difference between most oils thesedays as long as you stay within one group. ie: conventional or synthetic.
I do notice a difference between conventional, and synthetic oil. Not in power or economy, but in terms of pressure drop after long high-throttle pulls. I see less pressure loss (on other cars, my 220D is pegged at 45psi all the time) with Mobil 1 than I did with conventional oils.

The only synthetic I have used is Mobil 1, so I can't comment on that, but I would be interested in seeing some data compating the two.