This example is on a 190e 2.6, swapping the original 3.27 diff for one from a 2.3 16v with LSD (also 3.27).
For a list of possible gear-ratios, check here: http://mbturbo.com/gear-ratios/
Start by loosening the exhaust and the metal protector going around the cardanshaft right in front of the differential. They are going to be in the way (alot) when you’re lowering the differential and loosening things.
Next, we want to get the flanges on the flex disc loose. After you have removed the bolts for the flex disc, use a prybar to get the flanges free from the flex-disc. The disc has metal rings that locks into the flanges when tightened. If these are rusty, they will be stuck real good, and be a pain in the ass to get loose when your differential is down.
After this it’s time to loosen the XZN bolts on the sides of the differential. A good place for loosening these bolts are on the front side of the shafts. And a good tool to get the shafts standing still is the handbrake. So, get the bolt/shaft in position, tighten the handbrake, loosen the bolt – repeat 12 times.
After this comes the annoying and somewhat difficult part if you ask me. The differential on these cars are hold in place in the front by a allen head bolt, which can’t be loosened unless you lower the entire rear subframe or have some special tool.
So you loosen and lower one side of the subframe as shown on the pic, get the tool in place on the top side of the frame, and start loosening the allen screw from below.
After this you loosen the ASR sensor on the right side and the four bolts at the rear of the differential, and you should have a differential coming down!
Good luck!