It Won't Reverse

1994 E320.

Yesterday the thing stopped going in reverse! I put ATF in, and it actually seemed to fix it... until this evening! If the car is on a flat surface, it will go back a little bit, but if it's on any kind of hill it won't go back at all (if you're backing up the hill, which I often do.)

SO, what to do? Replace transmission? Or is there a cheaper alternative?

If there is plenty of ATF in the tranny then you may have big problems. Has it been leaking? Make sure you don't over fill it which can be damaging to the trans. I really don't know of a fix if it is slipping except a good mechanic. Does not have to be a MB dealer to do the job right and save some money.