Upgrading the rear differential oil on a w212 E350 CDI

[Psychil]

The w212's rear differential oil was just changed.

On Black Friday, I bought two 1-liter bottles of Fuchs Titan Sintopoid FE 75W-85 from Opie Oils for about £10 each, and it's listed as an acceptable fluid by Mercedes Bevo. Merc probably used that as the fluid in their bottles. Evidently, Fuchs is the only authorised provider of PAS fluid, as my recent thread on power steering fluid and the link to Bevo both indicate. Mercato clearly uses Fuchs extensively.


Both the differential's fill and drain plugs are 14 mm hex key, which is similar to a big allen key shape. A 14 mm sump key socket on a 3/8" square ratchet drive was part of my Laser sump key set, and it was the perfect match for the plug head. Prior to attempting to remove the drain plugs, clean them thoroughly and spray them with penetrating solution. Wait at least fifteen minutes.

I discovered that a 3/8" ratchet was sufficient to fit it into the gap between the exhaust, eliminating the requirement for a wobbling universal coupler.


I utilised this method since I was afraid of jacking up the differential; nevertheless, I am unable to guarantee the safety of jacking up, thus I cannot endorse it. Only on MOT ramps or a 4-post lift would I feel competent to accomplish this task.
Although many would recommend using axle stands, doing so exposes you to the possibility of jacking up the vehicle solely via the differential—which is already corroding after 12 years—and, in comparison to, say, a wheel and three feet of railway sleeper, I don't feel particularly secure under two neatly assembled axle supports with their relatively narrow bases. If the jack were to release, I would not be surprised if the heavily chunky and square-cut timber beneath the rear subframe could easily sustain the weight of the vehicle, especially with a wheel properly under the sill. Any 'drop' would be minor because there was less than 5mm of space between the subframe and the lumber and the wheel and between the sill and the wheel.

After raising the passenger side rear with a jack, I took the rear wheel off and placed it halfway under the car, under the sill and as near to the jack as I could get it. Under the rear subframe, I tucked a couple of large pieces of railway sleeper. beneath the watchful eye of an assistant who had received extensive training on how to use the jack, I snuck beneath the vehicle, cracked open the fill plug, and climbed back out. Only a few seconds.
Lower the vehicle to the ground after reattaching the wheel.

With the wheel beneath the sill and the railway sleepers under the rear subframe, I proceeded to jack up the driver's side using the identical procedure as described earlier. While under supervision, I slid under and completely undid the drain stopper, which I promptly dumped into the oil collect pan. In the space of twenty seconds beneath the vehicle.
After that, I cautiously lowered this side onto the jack to make the differential lean slightly towards the drain hole.
After the water had drained (which took around 20 minutes), I jack-knifed the vehicle again, this time positioning the related wheels and railway sleepers, and reinserted the drain plug from underneath. Roughly twenty seconds.
Once you've lowered it, put the wheel back on the driver's rear.

Once again, we must return to the rear of the vehicle on the passerger side, lift it up, remove the wheels, and place them under the sill, in addition to the railway sleepers. Noting that the car is sloping away from the fill hole, which causes a slight overfill of diff oil, I was able to remove the fill plug by reaching between the brake disc and the front of the rear wheel arch with a couple of socket extensions. I then filled up the differential without getting under the car by using a giant oil syringe/extractor with approximately 2 feet of clear, stiff poly hose.
Next, I levelled the vehicle by lowering it, which allowed the extra oil to drain to the proper level.
I jacked the car back up, set the wheel under the sill, etc., and then spent another 30 seconds whipping around under the car to fit the plug. After that, I quickly cleaned up with some baby wipes.

The job took approximately 90 minutes due to all the wheel on/wheel off, jack up/lower, repeat/repeat manoeuvres. However, I was more at ease with the car having three wheels on the ground, one under the sill and railway sleepers, and the front wheels chocked than with the rear wheels fully elevated on both sides using axle stands. This is especially true for rear wheel drive cars, where the front wheels are unrestricted by gears or handbrakes.

[Psychil]

https://operatingfluids.mercedes-benz.com/sheet/235.7

[VVC-Geeza]

Nice piece of writing, but please allow me to add anything. Loosen the filler plug before replenishing the diff fluid.

[Psychil]

Yes, I did that, and you can find it in the previous post.
I apologise for the delay in writing the post; it's conceivable that I was editing when you added this comment.
I started by posting the thread partially completed on my phone, which was too sluggish, and then switched to using a computer so I could type faster 👍.

[VVC-Geeza]

Yes, you did; it was my error. On two occasions, I have lifted my C55 using the differential, but each time, I have had to remove the metal heat sink, which is a major pain in and of itself. Rip the heat sink bolts, jack the car up one side, lower it back down, jack it under the differential and so on. The idea is clear. It hurts.

[paulh2602601]

Over the years, I've done it three or four times on each vehicle. Since my driveway is slanted, I level the car by driving it onto wheel ramps.
Fuchs and one of those inexpensive transfer pumps from eBay have always made refilling a breeze.
It’s such a cheap job as diy .