I have a 1999 E300TD with about 170k on it. It has developed a squeak that is almost constant at lower speeds. Other characteristics:

- A bump will exacerbate it, but it sounds like something is wiggling
- It is not noticable at highway speeds or 35+ really
- I have replaced the ball joints and a bushing of which the name escapes me
- The Dealer said there was nothing noticably wrong (I mentioned the squeak when in there for something else)
- It is not clear whether this is a front end or rear end noise - I would bet front if I had to
- I cannot reproduce the sound by pushing down on any corner of the car
- Car has been serviced recently (don't ask ;-) I usually do it nmyself but it died 2 miles from the MB dealership so I got lazy (and now poor))
- New exhaust so it isn't that wiggling up under there. (although I did not put on new rubber mounts)

My guess is that it is either a motor mount or the transmission mount. Does this seem like a reasonable conclusion? Do these things usually need replacement? In other words, if I put new ones on and that it is not it, then can I still feel OK that I did not waste my $$$ (!)

Any other ideas?

Thanks in advance!