W124 Reverse = Park?

[Savannah Buzz]

1993 300TE, 267K. Suddenly won't move in reverse, no slipping leading up to it. When shifter is moved to R, feels like engaged, but engine can rev and no movement of car. Tried in R position to roll back on an incline (backing down hill) - car moves slightly, then lurches to a stop, as if you had slammed it into park. When you move to N it still won't roll, have to move to D, inch forward (relieves some sort of "latch"?), then back to N, and it will roll down hill backwards. I would have thought if blown seal that it would move in R as if it were in the N position.

Thoughts, other than pull tranny and prepare for rebuild? Fluid normal, and changed fluid, no improvement. Filter? Anything in valve body I can adjust or replace?

Also, where's the best price on spheres for the rear suspension?