I changed the 3.07 differential in my 300SD with a 2.47 from a 1982 380SE. All told, it took me about 6 hours, start to finish. Even with snow falling, it wasn't that bad of a job.

Here are some parts/tools you will need if you undertake this project:

+ 30mm, 12 point deep socket to remove the drive shaft yoke on the diff. I bought one from SnapOn for about $40 (I bought the impact socket, non-impact sockets are cheaper.)

+ 12mm, 1.50 pitch lock nuts (qty 4), for the differential mounting studs.

+ this is a great time to replace the flex disc and the pinion bearing seal.

+ a floor jack with a tall reach. I bought the 2 ton aluminum floor jack from Costco for $100 and it worked well.

Here's a tip - put the clips on the axle shafts BEFORE you bolt the diff in place. I needed a thinner spacing washer, and had to remove all bolts and drop the diff to swap the washers.

Unfortunately, I don't drive the 300SD during the salt season in Chicago, so I will have a couple months before I can give a drive report. I track the mileage of each tank of gas, so I will be able to report any mileage improvements.