topping off rear differential w210
 

My rear differential on my 1999 e300td has somewhat of a leak. How difficult is it to check the fluid level, and top off if necessary? Any advice/experiences doing so are appreciated. Also, any recommendations on a particular differential/gear oil to use?

There is a fill plug on one side of the differential. It is a 17 mm allen head IIRC. Remove plug and add fluid till it runs out. After it stops running out reinstall plug. I typically use 75/90W synthetic different lube.

as engatwork said - use the filler plug, its exactly like the W124 (driver side of the diff).

The W210 were filled with regular SAE85W90 dino gear oil (the smelliest and thickest kind you will ever come across). If your diff is leaking then dont use a synthetic in there as it will super clean everything out and may make the leak worse.

get some cheap house brand gear oil from any store and top it up. Once you fix your leaks then fill up with synthetic.

I'd get some Lubro Moly 235.0 spec 85w90 gear oil, that should be what was originally spec'd in that car. It's non-synthetic but it is what's approved by MBZ for use in your diff. I used it in both my Benzes, including my W208 CLK430. I found it locally pretty reasonably-priced. I'm just a stickler for approved MB fluids.

Once you get the leak fixed, drain and fill with that same gear oil and motor happily.