hey,

had the same problem a while back, with my w124/722.433 transmission.


before pulling/replacing the transmission, try dropping the valve body and then inspecting the B2 brake band.


the problem could be that your b2 brake band needs to be adjusted via new(longer) thrust pin. its an inexpensive repair, a new longer thrust pin + retainer clip = $15-20 from dealer.

or

worse case scenario: broken b2 band = would require a rebuild


drop the valve body and take a better look.

good luck