What is This Noise?
 

It started last week. I have a 1988 300SE. It sounds just like a bad constant velocity joint (if the car were front wheel drive) but it is a very rubbery sounding clicking not metalic at all. It happens from a dead stop to about 25 mph going straight if you are on the gas 1/2 throttle or so or from a dead stop or rolling start of 5-10 mph if you are making a fairly sharp turn and are on the gas 1/4 throttle or more.

I have never heard anything like it and it sounds as if it is coming from the front of the car not the rear. A very rubbery sounding CV Joint is the best description I can give.

Unrelated, the car is also stall ing like mad so it's going to the shop tomorrow morning. With the rough idle I'm hoping it's the OVP, we'll see. I'll have them check out the noise and since it's getting warm soon, have them find the leak in my A/C system. ALWAYS something.

Check your dirve shaft.
You have flexible disks between the front of the drive shaft adn the tranny, the rear of the drive shaft and the differential.
Additionally you have a center drive shaft rubber support. Theis will deteriate over time and cause a "bumping noise" while accelerating or at a particular speed.