Find yourself a steep hill and stop pointed down the hill. Place the tranny in reverse and back up the hill. Its almost certain that if the reverse clutches (no band problem for reverse in this tranny) are in failure the thing will slip and or chatter as the gas is applied.
If this is the case, repairs should be handled sooner than later. Seventeen hundred is a fair price to have your transmission rebuilt. I would advise having someone with rebuild experience do this rather than just a parts exchanger. There are lots of adjustment issues and any warrantee adjustments will obviously be better accomplished by those who can fix the internals.
Bosch Master, ASE Master, L1
33 years MB technician