Differential oil filling

[SteveK]

I decided today was diff oil day so I took the car around the block a few times to heat things up and then parked it in the garage (level) and drained the differential.   I let it drain with the fill plug removed and all looked good.  But when I filled it up, it would only hold a little less than 2 quarts.  I took it around the block again and was then able to finish puting in the rest of the second quart.  The book says 2.5 liters which should be something like 2.7 quarts, so I should be around .7 quarts low.    Any ideas on what is going on?   

[paults1]

When the axles are at level, not all of the oil will drain out. I raise each axle one at a time with a jack under the trailing arm. Just a few inches up does the trick. 

Paul, '63 230SL

[SteveK]

Thanks, now that makes sense!  I put in some synthetic, so I think I'll run it for about 50 miles and then drain it again, the right way this time   By that time everything should be nice and clean so all new fresh oil will be good!

[Iconic]

This is slightly off topic, but specifically what oil did you use and can you report on whether or not you hear a difference?
Thank you !!

[SteveK]

I used Valvoline 80-90 weight synthetic.   Can't say that I can tell any difference in sound.   (My trunk is Dynamatted however which I suspect would mask most diff noise unless it was real bad)    Changing the oil is easy, a 14mm allen wrench removes both plugs.  I filled the diff connecting the bottle directly to a 4 ft. rubber hose which I ran from a wheel well to the fill plug. 

[Iconic]

Thank you.
I'm going to give Red Line a try.
The hose from the wheel well is a good idea. You just saved the world from one more disposable pump thrown into the garbage dump !!
Mark