I am in the process of removing the differential on my 1984 300SD. I am down to the four main bolts that hold the diff to the sub-frame. I can get my 19mm box end wrench on the nuts, but I can't enough leverage to break them free. Not enough room for my breaker bar. They are soaking in Busty tonight while I think about it some more.

Are there any hints/tips/tricks to removing these four nuts???

Slip a helper wrench over the other one?

Its tricky to explain...but you use the boxed in end of one wrench (an extra) and put it on the open end of the wrench you are trying to turn with in such a way you can get way more leverage. The only downside is...non-quality tools will break

What's Busty?

If it's like Liquid Wrench, then that should do it. But in like 10 miuntes or so...

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'87 924S
'81 280SEL

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81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

Busty is a penetrating oil.
http://www.hogwash.com/Busty%20Penetrating%20Oil.htm

Heating up the part that the bolts are threaded into will tend to expand it, make penetrating oil soak in faster, and make removal easier. It's best if heating is done quickly to minimize heating of the bolts.

At this point I'm going to presume you have the driveshaft off and the rear differential mount removed (the one that is attached to the rear cover of the differential.

You should have the back end of the car up on jackstands, being held by the frame - I think I did this either at the subframe mount points or further back near the rear sway bar mounts. Make darned sure the car is stable at this point, because you have little crush protection as the differential comes out, because that helps hold the subframe in place which in turn holds the rear wheels.

The problem you are having with clearance has to do with the subframe position. With the frame up on jackstands, as you push the wheel ends of the subframe upward, the differential will drop down, allowing you more access to the bolts. You can figure out your own method of holding the wheels up - I think I used a bottle jack somehow.

A lot of times I use extra wheels (lying on their sides) as crush protection by putting them under the frame. You really have to get pretty far under the car for the differential work and I fear not only for myself but others. I seem to remember spending a lot of time completely under the car in the vicinity of the front of the differential to get the front two bolts off.

Please be careful.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles