1997 Mercedes C230 Drive Line Issue

[Jamison]

Good Morning,

I have a 1997 Mercedes Benz C230 with over 240k miles on it. Recently, while driving my car, I noticed a weird humming noise, from what I thought was possibly the transmission. The noise went away for a few drives, then one day, something sounded like it fell from it's place in the Drivetrain. I took my car home with a extremely loud humming noise, which now I think I've located to the Differential. Upon finally getting my car home, it felt like the wheels locked up and would no longer move freely. Now that I've had my car parked, I'm having issues with getting the car out of park, the Shifter is loose feeling and won't engage into any gears. I lifted up the car and have drained the transmission oil pan to see if there was any metal there, none found, except for some very dirty oil. My question is to you all, is there any way to full diagnose this possible Differential failure, without having any damage to the rest of the Drivetrain? This is my first time dealing with a Mercedes model, so the repairs are new to me. Also, is there a tool kit for removing the special bolts attached to the axles? They are a new type of bolt, that I've not seen before.

Thanks in advance for any guidance you all can give!

Jamison

P.S. I purchased Flex Drive joints because I thought those may be the problem. But I fear it's much worse.

P.P.S. Pictures of the Drivetrain can be available upon request!